| o-glucosylation of cis-zeatin in maize. characterization of genes, enzymes, and endogenous cytokinins. | trans-zeatin is a major and ubiquitous cytokinin in higher plants. cis-zeatin has traditionally been viewed as an adjunct with low activity and rare occurrence. recent reports of cis-zeatin and its derivatives as the predominant cytokinin components in some plant tissues may call for a different perspective on cis-isomers. the existence of a maize (zea mays) gene (ciszog1) encoding an o-glucosyltransferase specific to cis-zeatin (r.c. martin, m.c. mok, j.e. habben, d.w.s. mok [2001] proc natl ac ... | 2003 | 12644686 |
| whole-genome comparison of leucine-rich repeat extensins in arabidopsis and rice. a conserved family of cell wall proteins form a vegetative and a reproductive clade. | we have searched the arabidopsis and rice (oryza sativa) genomes for homologs of lrx1, an arabidopsis gene encoding a novel type of cell wall protein containing a leucine-rich repeat (lrr) and an extensin domain. eleven and eight lrx (lrr/extensin) genes have been identified in these two plant species, respectively. the lrx gene family encodes proteins characterized by a short n-terminal domain, a domain with 10 lrrs, a cysteine-rich motif, and a variable c-terminal extensin-like domain. phyloge ... | 2003 | 12644681 |
| the medicago species a2-type cyclin is auxin regulated and involved in meristem formation but dispensable for endoreduplication-associated developmental programs. | phytohormones as well as temporal and spatial regulation of the cell cycle play a key role in plant development. here, we investigated the function and regulation of an alfalfa (medicago sativa) a2-type cyclin in three distinct root developmental programs: in primary and secondary root development, nodule development, and nematode-elicited gall formation. using transgenic plants carrying the medsa;cyca2;2 promoter-beta-glucuronidase gene fusion, in combination with other techniques, cyca2;2 expr ... | 2003 | 12644661 |
| the dornroschen/enhancer of shoot regeneration1 gene of arabidopsis acts in the control of meristem ccll fate and lateral organ development. | the two main tasks of a meristem, self-perpetuation and organ initiation, are separated spatially. slowly dividing cells in the meristem center act as pluripotent stem cells, and only their derivatives in the meristem periphery specify new organs. meristem integrity and cellular proliferation are controlled in part by regulatory interactions between genes that are expressed in specific subdomains of the meristem. using transposon-mediated activation tagging, we have identified dornröschen (drn-d ... | 2003 | 12615942 |
| cell polarity and pin protein positioning in arabidopsis require sterol methyltransferase1 function. | plants have many polarized cell types, but relatively little is known about the mechanisms that establish polarity. the orc mutant was identified originally by defects in root patterning, and positional cloning revealed that the affected gene encodes sterol methyltransferase1, which is required for the appropriate synthesis and composition of major membrane sterols. smt1(orc) mutants displayed several conspicuous cell polarity defects. columella root cap cells revealed perturbed polar positionin ... | 2003 | 12615936 |
| leader proteinase of beet yellows virus functions in long-distance transport. | the 66-kda leader proteinase (l-pro) of the beet yellows virus (byv) possesses a nonconserved n-terminal domain and a conserved, papain-like c-terminal domain. previous work revealed that the n-terminal domain functions in rna amplification, whereas the c-terminal domain is required for autoproteolysis. alanine-scanning mutagenesis was applied to complete the functional analysis of l-pro throughout the virus life cycle. this analysis indicated that the c-terminal domain of l-pro, in addition to ... | 2003 | 12584307 |
| atidb: arabidopsis thaliana insertion database. | insertional mutagenesis techniques, including transposon- and t-dna-mediated mutagenesis, are key resources for systematic identification of gene function in the model plant species arabidopsis thaliana. we have developed a database (http://atidb.cshl.org/) for archiving, searching and analyzing insertional mutagenesis lines. flanking sequences from approximately 10 500 insertion lines (including transposon and t-dna insertions) from several tagging programs in arabidopsis were mapped to the gen ... | 2003 | 12582244 |
| arabidopsis leafy cotyledon1 represents a functionally specialized subunit of the ccaat binding transcription factor. | leafy cotyledon1 (lec1) is a central regulator that is required for many aspects of arabidopsis embryogenesis and sufficient to induce embryo development in vegetative cells when expressed ectopically. we previously showed that lec1 encodes an hap3 subunit of the ccaat binding factor and that the 10 arabidopsis hap3 (ahap3) subunits can be divided into two classes, the lec1-type and the non-lec1-type, based on sequence similarity within their b domains. by analyzing the ability of chimeric hap3 ... | 2003 | 12578989 |
| low temperature inhibits rna silencing-mediated defence by the control of sirna generation. | temperature dramatically affects plant-virus interactions. outbreaks of virus diseases are frequently associated with low temperature, while at high temperature viral symptoms are often attenuated (heat masking) and plants rapidly recover from virus diseases. however, the underlying mechanisms of these well-known observations are not yet understood. rna silencing is a conserved defence system of eukaryotic cells, which operates against molecular parasites including viruses and transgenes. here w ... | 2003 | 12554663 |
| metabolic engineering of valine- and isoleucine-derived glucosinolates in arabidopsis expressing cyp79d2 from cassava. | glucosinolates are amino acid-derived natural products that, upon hydrolysis, typically release isothiocyanates with a wide range of biological activities. glucosinolates play a role in plant defense as attractants and deterrents against herbivores and pathogens. a key step in glucosinolate biosynthesis is the conversion of amino acids to the corresponding aldoximes, which is catalyzed by cytochromes p450 belonging to the cyp79 family. expression of cyp79d2 from cassava (manihot esculenta crantz ... | 2003 | 12586901 |
| the role of free histidine in xylem loading of nickel in alyssum lesbiacum and brassica juncea. | exposure of the hyperaccumulator alyssum lesbiacum to nickel (ni) is known to result in a dose-dependent increase in xylem sap concentrations of ni and the chelator free histidine (his). addition of equimolar concentrations of exogenous l-his to an ni-amended hydroponic rooting medium enhances ni flux into the xylem in the nonaccumulator alyssum montanum, and, as reported here, in brassica juncea l. cv vitasso. in b. juncea, reducing the entry of l-his into the root by supplying d-his instead of ... | 2003 | 12586895 |
| overexpression of arabidopsis phytochelatin synthase paradoxically leads to hypersensitivity to cadmium stress. | phytochelatin (pc) plays an important role in heavy metal detoxification in plants and other living organisms. therefore, we overexpressed an arabidopsis pc synthase (atpcs1) in transgenic arabidopsis with the goal of increasing pc synthesis, metal accumulation, and metal tolerance in these plants. transgenic arabidopsis plants were selected, designated pcs lines, and analyzed for tolerance to cadmium (cd). transgenic pcs lines showed 12- to 25-fold higher accumulation of atpcs1 mrna, and produc ... | 2003 | 12586889 |
| atcsla7, a cellulose synthase-like putative glycosyltransferase, is important for pollen tube growth and embryogenesis in arabidopsis. | the cellulose synthase-like proteins are a large family of proteins in plants thought to be processive polysaccharide beta-glycosyltransferases. we have characterized an arabidopsis mutant with a transposon insertion in the gene encoding atcsla7 of the csla subfamily. analysis of the transmission efficiency of the insertion indicated that atcsla7 is important for pollen tube growth. moreover, the homozygous insertion was embryo lethal. a detailed analysis of seed developmental progression reveal ... | 2003 | 12586879 |
| wvd2 and wdl1 modulate helical organ growth and anisotropic cell expansion in arabidopsis. | wild-type arabidopsis roots develop a wavy pattern of growth on tilted agar surfaces. for many arabidopsis ecotypes, roots also grow askew on such surfaces, typically slanting to the right of the gravity vector. we identified a mutant, wvd2-1, that displays suppressed root waving and leftward root slanting under these conditions. these phenotypes arise from transcriptional activation of the novel wave-dampened2 (wvd2) gene by the cauliflower mosaic virus 35s promoter in mutant plants. seedlings ... | 2003 | 12586874 |
| auxin acts in xylem-associated or medullary cells to mediate apical dominance. | a role for auxin in the regulation of shoot branching was described originally in the thimann and skoog model, which proposes that apically derived auxin is transported basipetally directly into the axillary buds, where it inhibits their growth. subsequent observations in several species have shown that auxin does not enter axillary buds directly. we have found similar results in arabidopsis. grafting studies indicated that auxin acts in the aerial tissue; hence, the principal site of auxin acti ... | 2003 | 12566587 |
| biosynthesis and emission of terpenoid volatiles from arabidopsis flowers. | arabidopsis is believed to be mostly self-pollinated, although several lines of genetic and morphological evidence indicate that insect-mediated outcrossing occurs with at least a low frequency in wild populations. here, we show that arabidopsis flowers emit both monoterpenes and sesquiterpenes, potential olfactory cues for pollinating insects. of the 32 terpene synthase genes in the arabidopsis genome, 20 were found to be expressed in flowers, 6 of these exclusively or almost exclusively so. tw ... | 2003 | 12566586 |
| cipk3, a calcium sensor-associated protein kinase that regulates abscisic acid and cold signal transduction in arabidopsis. | plants respond to environmental stress by activating "stress genes." the plant hormone abscisic acid (aba) plays an important role in stress-responsive gene expression. although ca(2+) serves as a common second messenger in signaling stress and aba, little is known about the molecular basis of ca(2+) action in these pathways. here, we show that cipk3, a ser/thr protein kinase that associates with a calcineurin b-like calcium sensor, regulates aba response during seed germination and aba- and str ... | 2003 | 12566581 |
| the beta-subunit of the arabidopsis g protein negatively regulates auxin-induced cell division and affects multiple developmental processes. | plant cells respond to low concentrations of auxin by cell expansion, and at a slightly higher concentration, these cells divide. previous work revealed that null mutants of the alpha-subunit of a putative heterotrimeric g protein (gpa1) have reduced cell division. here, we show that this prototypical g protein complex acts mechanistically by controlling auxin sensitivity toward cell division. loss-of-function g protein mutants have altered auxin-mediated cell division throughout development, es ... | 2003 | 12566580 |
| the arabidopsis cax1 mutant exhibits impaired ion homeostasis, development, and hormonal responses and reveals interplay among vacuolar transporters. | the arabidopsis ca(2+)/h(+) transporter cax1 (cation exchanger1) may be an important regulator of intracellular ca(2+) levels. here, we describe the preliminary localization of cax1 to the tonoplast and the molecular and biochemical characterization of cax1 mutants. we show that these mutants exhibit a 50% reduction in tonoplast ca(2+)/h(+) antiport activity, a 40% reduction in tonoplast v-type h(+)-translocating atpase activity, a 36% increase in tonoplast ca(2+)-atpase activity, and increased ... | 2003 | 12566577 |
| the arabidopsis srr1 gene mediates phyb signaling and is required for normal circadian clock function. | plants possess several photoreceptors to sense the light environment. in arabidopsis cryptochromes and phytochromes play roles in photomorphogenesis and in the light input pathways that synchronize the circadian clock with the external world. we have identified srr1 (sensitivity to red light reduced), a gene that plays an important role in phytochrome b (phyb)-mediated light signaling. the recessive srr1 null allele and phyb mutants display a number of similar phenotypes indicating that srr1 is ... | 2003 | 12533513 |
| arabidopsis tobamovirus multiplication (tom) 2 locus encodes a transmembrane protein that interacts with tom1. | the tom2-1 mutation of arabidopsis thaliana reduces the efficiency of intracellular multiplication of tobamoviruses. the tom2-1 mutant was derived from fast-neutron-irradiated seeds, and the original mutant line also carries ttm1, a dominant modifier that increases tobamovirus multiplication efficiency in a tobamovirus-strain-specific manner in the tom2-1 genetic background. here, we show that the tom2-1 mutation involved a deletion of approximately 20 kb in the nuclear genome. the deleted regio ... | 2003 | 12514139 |
| rna target sequences promote spreading of rna silencing. | it is generally recognized that a silencing-inducing locus can efficiently reduce the expression of genes that give rise to transcripts partially homologous to those produced by the silencing-inducing locus (primary targets). interestingly, the expression of genes that produce transcripts without homology to the silencing-inducing locus (secondary targets) can also be decreased dramatically via transitive rna silencing. this phenomenon requires primary target rnas that contain sequences homologo ... | 2003 | 12529532 |
| the arabidopsis atipt8/pga22 gene encodes an isopentenyl transferase that is involved in de novo cytokinin biosynthesis. | cytokinin plays a critical role in plant growth and development by stimulating cell division and cell differentiation. despite many years' research efforts, our current understanding of this hormone is still limited regarding both its biosynthesis and signaling. to genetically dissect the cytokinin pathway, we have used a functional screen to identify arabidopsis gain-of-function mutations that enable shoot formation in the absence of exogenous cytokinins. by using a chemical-inducible activatio ... | 2003 | 12529525 |
| diversity of the superfamily of phloem lectins (phloem protein 2) in angiosperms. | phloem protein 2 (pp2) is one of the most abundant and enigmatic proteins in the phloem sap. although thought to be associated with structural p-protein, pp2 is translocated in the assimilate stream where its lectin activity or rna-binding properties can exert effects over long distances. analyzing the diversity of these proteins in vascular plants led to the identification of pp2-like genes in species from 17 angiosperm and gymnosperm genera. this wide distribution of pp2 genes in the plant kin ... | 2003 | 12529520 |
| the sucrose transporter stsut1 localizes to sieve elements in potato tuber phloem and influences tuber physiology and development. | the sucrose (suc) h(+)-cotransporter stsut1 from potato (solanum tuberosum), which is essential for long-distance transport of suc and assumed to play a role in phloem loading in mature leaves, was found to be expressed in sink tubers. to answer the question of whether sut1 serves a function in phloem unloading in tubers, the promoter was fused to gusa and expression was analyzed in transgenic potato. sut1 expression was unexpectedly detected not in tuber parenchyma but in the phloem of sink tub ... | 2003 | 12529519 |
| dual role of toc1 in the control of circadian and photomorphogenic responses in arabidopsis. | to examine the role of the toc1 (timing of cab expression1) gene in the arabidopsis circadian system, we generated a series of transgenic plants expressing a gradation in toc1 levels. silencing of the toc1 gene causes arrhythmia in constant darkness and in various intensities of red light, whereas in blue light, the clock runs faster in silenced plants than in wild-type plants. increments in toc1 gene dosage delayed the pace of the clock, whereas toc1 overexpression abolished rhythmicity in all ... | 2003 | 12509533 |
| the arabidopsis ref2 mutant is defective in the gene encoding cyp83a1 and shows both phenylpropanoid and glucosinolate phenotypes. | the arabidopsis ref2 mutant was identified in a screen for plants having altered fluorescence under uv light. characterization of the ref2 mutants showed that they contained reduced levels of a number of phenylpropanoid pathway-derived products: sinapoylmalate in leaves, sinapoylcholine in seeds, and syringyl lignin in stems. surprisingly, positional cloning of the ref2 locus revealed that it encodes cyp83a1, a cytochrome p450 sharing a high degree of similarity to cyp83b1, an enzyme involved in ... | 2003 | 12509530 |
| arabidopsis atmyc2 (bhlh) and atmyb2 (myb) function as transcriptional activators in abscisic acid signaling. | in arabidopsis, the induction of a dehydration-responsive gene, rd22, is mediated by abscisic acid (aba). we reported previously that myc and myb recognition sites in the rd22 promoter region function as cis-acting elements in the drought- and aba-induced gene expression of rd22. bhlh- and myb-related transcription factors, rd22bp1 (renamed atmyc2) and atmyb2, interact specifically with the myc and myb recognition sites, respectively, in vitro and activate the transcription of the beta-glucuroni ... | 2003 | 12509522 |
| enhanced transcription of the arabidopsis disease resistance genes rpw8.1 and rpw8.2 via a salicylic acid-dependent amplification circuit is required for hypersensitive cell death. | the arabidopsis disease resistance (r) genes rpw8.1 and rpw8.2 couple the recognition of powdery mildew pathogens of this plant with the subsequent induction of a localized necrosis, or hypersensitive response (hr). the hr restricts the spread of the infection and renders the plant resistant. one-third of arabidopsis plants transformed with a genomic fragment containing rpw8.1 and rpw8.2 developed spontaneous hr-like lesions (shl) in the absence of pathogens. we demonstrate that shl occurs in tr ... | 2003 | 12509520 |
| the arabidopsis sos5 locus encodes a putative cell surface adhesion protein and is required for normal cell expansion. | cell surface proteoglycans have been implicated in many aspects of plant growth and development, but genetic evidence supporting their function has been lacking. here, we report that the salt overly sensitive5 (sos5) gene encodes a putative cell surface adhesion protein and is required for normal cell expansion. the sos5 mutant was isolated in a screen for arabidopsis salt-hypersensitive mutants. under salt stress, the root tips of sos5 mutant plants swell and root growth is arrested. the root-s ... | 2003 | 12509519 |
| leafy cotyledon1-like defines a class of regulators essential for embryo development. | arabidopsis leafy cotyledon1 (lec1) is a critical regulator required for normal development during the early and late phases of embryogenesis that is sufficient to induce embryonic development in vegetative cells. lec1 encodes a hap3 subunit of the ccaat binding transcription factor. we show that the 10 arabidopsis hap3 (ahap3) subunits can be divided into two classes based on sequence identity in their central, conserved b domain. lec1 and its most closely related subunit, lec1-like (l1l), cons ... | 2003 | 12509518 |
| a sugar beet chlorophyll a/b binding protein promoter void of g-box like elements confers strong and leaf specific reporter gene expression in transgenic sugar beet. | modification of leaf traits in sugar beet requires a strong leaf specific promoter. with such a promoter, expression in taproots can be avoided which may otherwise take away available energy resources for sugar accumulation. | 2004 | 15579211 |
| the role of [delta]1-pyrroline-5-carboxylate dehydrogenase in proline degradation. | in response to stress, plants accumulate pro, requiring degradation after release from adverse conditions. delta1-pyrroline-5-carboxylate dehydrogenase (p5cdh), the second enzyme for pro degradation, is encoded by a single gene expressed ubiquitously. to study the physiological function of p5cdh, t-dna insertion mutants in atp5cdh were isolated and characterized. although pro degradation was undetectable in p5cdh mutants, neither increased pro levels nor an altered growth phenotype were observed ... | 2004 | 15548746 |
| the essential basic helix-loop-helix protein fit1 is required for the iron deficiency response. | regulation of iron uptake is critical for plant survival. although the activities responsible for reduction and transport of iron at the plant root surface have been described, the genes controlling these activities are largely unknown. we report the identification of the essential gene fe-deficiency induced transcription factor 1 (fit1), which encodes a putative transcription factor that regulates iron uptake responses in arabidopsis thaliana. like the fe(iii) chelate reductase fro2 and high af ... | 2004 | 15539473 |
| arabidopsis wpp-domain proteins are developmentally associated with the nuclear envelope and promote cell division. | the nuclear envelope (ne) acts as a selective barrier to macromolecule trafficking between the nucleus and the cytoplasm and undergoes a complex reorganization during mitosis. different eukaryotic kingdoms show specializations in ne function and composition. in contrast with vertebrates, the protein composition of the ne and the function of ne proteins are barely understood in plants. mfp1 attachment factor 1 (maf1) is a plant-specific ne-associated protein first identified in tomato (lycopersic ... | 2004 | 15548735 |
| diversification and alteration of recognition specificity of the pollen ligand sp11/scr in self-incompatibility of brassica and raphanus. | the recognition specificity of the pollen ligand of self-incompatibility (sp11/scr) was investigated using brassica rapa transgenic plants expressing sp11 transgenes, and sp11 of raphanus sativus s-21 was found to have the same recognition specificity as that of b. rapa s-9. in a set of three s haplotypes, whose sequence identities of sp11 and srk are fairly high, r. sativus s-6 showed the same recognition specificity as brassica oleracea s-18 and a slightly different specificity from b. rapa s- ... | 2004 | 15548734 |
| identification of the arabidopsis palmitoyl-monogalactosyldiacylglycerol delta7-desaturase gene fad5, and effects of plastidial retargeting of arabidopsis desaturases on the fad5 mutant phenotype. | hexadeca 7,10,13-trienoic acid (16:3delta(7,10,13)) is one of the most abundant fatty acids in arabidopsis (arabidopsis thaliana) and a functional component of thylakoid membranes, where it is found as an sn-2 ester of monogalactosyldiacylglycerol. the arabidopsis fad5 mutant lacks activity of the plastidial palmitoyl-monogalactosyldiacylglycerol delta7-desaturase fad5, and is characterized biochemically by the absence of 16:3delta(7,10,13) and physiologically by reduced chlorophyll content and ... | 2004 | 15579662 |
| promoter analysis of the barley pht1;1 phosphate transporter gene identifies regions controlling root expression and responsiveness to phosphate deprivation. | previous studies have shown that the promoter from the barley (hordeum vulgare) phosphate transporter gene, hvpht1;1, activates high levels of expression in rice (oryza sativa) roots and that the expression level was induced by up to 4-fold in response to phosphorus (p) deprivation. to identify promoter regions controlling gene regulation specificities, successive promoter truncations were made and attached to reporter genes. promoters of between 856 and 1,400 nucleotides activated gene expressi ... | 2004 | 15542491 |
| progression through meiosis i and meiosis ii in arabidopsis anthers is regulated by an a-type cyclin predominately expressed in prophase i. | meiosis is often described as a special case of cell division since it differs from mitosis in having two nuclear divisions without an intervening s-phase. it will be of great interest to uncover what molecular mechanisms underlie these special features of meiosis. we previously reported that the tardy asynchronous meiosis (tam) mutant of arabidopsis (arabidopsis thaliana) is slower in cell cycle progression in male meiosis. here we report that tam encodes the a-type cyclin, cyca1;2. the point m ... | 2004 | 15557098 |
| nuclear sdh2-1 and sdh2-2 genes, encoding the iron-sulfur subunit of mitochondrial complex ii in arabidopsis, have distinct cell-specific expression patterns and promoter activities. | three different nuclear genes encode the essential iron-sulfur subunit of mitochondrial complex ii (succinate dehydrogenase) in arabidopsis (arabidopsis thaliana), raising interesting questions about their origin and function. to find clues about their role, we have undertaken a detailed analysis of their expression. two genes (sdh2-1 and sdh2-2) that likely arose via a relatively recent duplication event are expressed in all organs from adult plants, whereas transcripts from the third gene (sdh ... | 2004 | 15563621 |
| reorganization and in vivo dynamics of microtubules during arabidopsis root hair development. | root hairs emerge from epidermal root cells (trichoblasts) and differentiate by highly localized tip growth. microtubules (mts) are essential for establishing and maintaining the growth polarity of root hairs. the current knowledge about the configuration of the mt cytoskeleton during root hair development is largely based on experiments on fixed material, and reorganization and in vivo dynamics of mts during root hair development is at present unclear. this in vivo study provides new insights i ... | 2004 | 15557102 |
| intracellular trafficking of nucleic acids. | until recently, the attention of most researchers has focused on the first and last steps of gene transfer, namely delivery to the cell and transcription, in order to optimise transfection and gene therapy. however, over the past few years, researchers have realised that the intracellular trafficking of plasmids is more than just a "black box" and is actually one of the major barriers to effective gene delivery. after entering the cytoplasm, following direct delivery or endocytosis, plasmids or ... | 2004 | 16296725 |
| manipulation of det1 expression in tomato results in photomorphogenic phenotypes caused by post-transcriptional gene silencing. | the tomato high pigment-2 gene encodes an orthologue of the arabidopsis nuclear protein de-etiolated 1 (det1). from genetic analyses it has been proposed that det1 is a negative regulator of light signal transduction, and recent results indicate that it may control light-regulated gene expression at the level of chromatin remodelling. to gain further understanding about the function of det1 during plant development, we generated a range of overexpression constructs and introduced them into tomat ... | 2004 | 15469492 |
| rearrangements in the cf-9 disease resistance gene cluster of wild tomato have resulted in three genes that mediate avr9 responsiveness. | cf resistance genes in tomato confer resistance to the fungal leaf pathogen cladosporium fulvum. both the well-characterized resistance gene cf-9 and the related 9dc gene confer resistance to strains of c. fulvum that secrete the avr9 protein and originate from the wild tomato species lycopersicon pimpinellifolium. we show that 9dc and cf-9 are allelic, and we have isolated and sequenced the complete 9dc cluster of l. pimpinellifolium la1301. this 9dc cluster harbors five full-length cf homologs ... | 2004 | 15579714 |
| an arabidopsis thaliana plasma membrane proton pump is essential for pollen development. | the plasma membrane proton pump (h(+)-atpase) found in plants and fungi is a p-type atpase with a polypeptide sequence, structure, and in vivo function similar to the mammalian sodium pump (na(+), k(+)-atpase). despite its hypothetical importance for generating and maintaining the proton motive force that energizes the carriers and channels that underlie plant nutrition, genetic evidence for such a central function has not yet been reported. using a reverse genetic approach for investigating eac ... | 2004 | 15579716 |
| accumulation of photosystem one1, a member of a novel gene family, is required for accumulation of [4fe-4s] cluster-containing chloroplast complexes and antenna proteins. | to investigate the nuclear-controlled mechanisms of [4fe-4s] cluster assembly in chloroplasts, we selected arabidopsis thaliana mutants with a decreased content of photosystem i (psi) containing three [4fe-4s] clusters. one identified gene, accumulation of photosystem one1 (apo1), belongs to a previously unknown gene family with four defined groups (apo1 to apo4) only found in nuclear genomes of vascular plants. all homologs contain two related motifs of approximately 100 amino acid residues tha ... | 2004 | 15494558 |
| structure-function analysis of the presumptive arabidopsis auxin permease aux1. | we have investigated the subcellular localization, the domain topology, and the amino acid residues that are critical for the function of the presumptive arabidopsis thaliana auxin influx carrier aux1. biochemical fractionation experiments and confocal studies using an n-terminal yellow fluorescent protein (yfp) fusion observed that aux1 colocalized with plasma membrane (pm) markers. because of its pm localization, we were able to take advantage of the steep ph gradient that exists across the pl ... | 2004 | 15486104 |
| a novel molecular recognition motif necessary for targeting photoactivated phytochrome signaling to specific basic helix-loop-helix transcription factors. | the phytochrome (phy) family of sensory photoreceptors (phya to phye) in arabidopsis thaliana control plant developmental transitions in response to informational light signals throughout the life cycle. the photoactivated conformer of the photoreceptor pfr has been shown to translocate into the nucleus where it induces changes in gene expression by an unknown mechanism. here, we have identified two basic helix-loop-helix (bhlh) transcription factors, designated phytochrome-interacting factor5 ( ... | 2004 | 15486100 |
| the arabidopsis csn5a and csn5b subunits are present in distinct cop9 signalosome complexes, and mutations in their jamm domains exhibit differential dominant negative effects on development. | the cop9 signalosome (csn) is an evolutionarily conserved multisubunit protein complex involved in a variety of signaling and developmental processes through the regulation of protein ubiquitination and degradation. a known biochemical role attributed to csn is a metalloprotease activity responsible for the derubylation of cullins, core components for several types of ubiquitin e3 ligases. the csn's derubylation catalytic center resides in its subunit 5, which in arabidopsis thaliana is encoded ... | 2004 | 15486099 |
| telomerase activator1 induces telomerase activity and potentiates responses to auxin in arabidopsis. | telomerase activity is highly regulated, abundant in rapidly dividing cells and reproductive organs, but undetectable in most other differentiated tissues. little is known about mechanisms that regulate telomerase. here, we used a biochemical assay to screen activation-tagged lines of arabidopsis thaliana for mutants that ectopically express this enzyme in their leaves. in one such mutant, a previously uncharacterized zinc-finger protein we designate telomerase activator1 (tac1) is overexpressed ... | 2004 | 15486103 |
| characterization of a xyloglucan endotransglucosylase gene that is up-regulated by gibberellin in rice. | xyloglucan endotransglucosylases/hydrolases (xths) that mediate cleavage and rejoining of the beta (1-4)-xyloglucans of the primary cell wall are considered to play an important role in the construction and restructuring of xyloglucan cross-links. a novel rice (oryza sativa) xth-related gene, osxth8, was cloned and characterized after being identified by cdna microarray analysis of gibberellin-induced changes in gene expression in rice seedlings. osxth8 was a single copy gene; its full-length cd ... | 2004 | 15516498 |
| the arabidopsis trehalose-6-p synthase attps1 gene is a regulator of glucose, abscisic acid, and stress signaling. | in arabidopsis (arabidopsis thaliana), trehalose is present at almost undetectable levels, excluding its role as an osmoprotectant. here, we report that overexpression of attps1 in arabidopsis using the 35s promoter led to a small increase in trehalose and trehalose-6-p levels. in spite of this, transgenic plants displayed a dehydration tolerance phenotype without any visible morphological alterations, except for delayed flowering. moreover, seedlings overexpressing attps1 exhibited glucose (glc ... | 2004 | 15516499 |
| aria, an arabidopsis arm repeat protein interacting with a transcriptional regulator of abscisic acid-responsive gene expression, is a novel abscisic acid signaling component. | arabidopsis (arabidopsis thaliana) genome contains more than 90 armadillo (arm) repeat proteins. however, their functions are largely unknown. here, we report that an arabidopsis arm repeat protein is involved in abscisic acid (aba) response. we carried out two-hybrid screens to identify signaling components that modulate aba-responsive gene expression. employing a transcription factor, abf2, which controls the aba-dependent gene expression via the g-box type aba-responsive elements, we isolated ... | 2004 | 15516505 |
| ca2+ dynamics in a pollen grain and papilla cell during pollination of arabidopsis. | ca2+ dynamics in the growing pollen tube have been well documented in vitro using germination assays and ca2+ imaging techniques. however, very few in vivo studies of ca2+ in the pollen grain and papilla cell during pollination have been performed. we expressed yellow cameleon, a ca2+ indicator based on green fluorescent protein, in the pollen grains and papilla cells of arabidopsis (arabidopsis thaliana) and monitored ca2+ dynamics during pollination. in the pollen grain, [ca2+]cyt increased at ... | 2004 | 15489279 |
| versatile gene-specific sequence tags for arabidopsis functional genomics: transcript profiling and reverse genetics applications. | microarray transcript profiling and rna interference are two new technologies crucial for large-scale gene function studies in multicellular eukaryotes. both rely on sequence-specific hybridization between complementary nucleic acid strands, inciting us to create a collection of gene-specific sequence tags (gsts) representing at least 21,500 arabidopsis genes and which are compatible with both approaches. the gsts were carefully selected to ensure that each of them shared no significant similari ... | 2004 | 15489341 |
| isolation and characterization of an arabidopsis mutant that overaccumulates o-acetyl-l-ser. | o-acetyl-l-ser (oas) is a positive regulator for the expression of sulfur (s) deficiency-inducible genes. in this study, through the isolation and analysis of arabidopsis mutants exhibiting altered expression of s-responsive genes, we identified a thiol reductase as a regulator of the oas levels. ethyl methanesulfonate-mutagenized m2 seeds of transgenic arabidopsis nob7 carrying a chimeric s-responsive promoter driving the green fluorescent protein gene were screened for mutants with altered lev ... | 2004 | 15466229 |
| uncoupling the effects of abscisic acid on plant growth and water relations. analysis of sto1/nced3, an abscisic acid-deficient but salt stress-tolerant mutant in arabidopsis. | we have identified a t-dna insertion mutation of arabidopsis (ecotype c24), named sto1 (salt tolerant), that results in enhanced germination on both ionic (nacl) and nonionic (sorbitol) hyperosmotic media. sto1 plants were more tolerant in vitro than wild type to na(+) and k(+) both for germination and subsequent growth but were hypersensitive to li(+). postgermination growth of the sto1 plants on sorbitol was not improved. analysis of the amino acid sequence revealed that sto1 encodes a 9-cis-e ... | 2004 | 15466233 |
| arabidopsis seedling growth response and recovery to ethylene. a kinetic analysis. | responses to the plant hormone ethylene are mediated by a family of five receptors in arabidopsis that act in the absence of ethylene as negative regulators of response pathways. in this study, we examined the rapid kinetics of growth inhibition by ethylene and growth recovery after ethylene withdrawal in hypocotyls of etiolated seedlings of wild-type and ethylene receptor-deficient arabidopsis lines. this analysis revealed that there are two phases to growth inhibition by ethylene in wild type: ... | 2004 | 15466220 |
| reserve mobilization in the arabidopsis endosperm fuels hypocotyl elongation in the dark, is independent of abscisic acid, and requires phosphoenolpyruvate carboxykinase1. | arabidopsis thaliana is used as a model system to study triacylglycerol (tag) accumulation and seed germination in oilseeds. here, we consider the partitioning of these lipid reserves between embryo and endosperm tissues in the mature seed. the arabidopsis endosperm accumulates significant quantities of storage lipid, and this is effectively catabolized upon germination. this lipid differs in composition from that in the embryo and has a specific function during germination. removing the endospe ... | 2004 | 15367715 |
| phytochrome phosphorylation modulates light signaling by influencing the protein-protein interaction. | plant photoreceptor phytochromes are phosphoproteins, but the question as to the functional role of phytochrome phosphorylation has remained to be elucidated. we investigated the functional role of phytochrome phosphorylation in plant light signaling using a pfr-specific phosphorylation site mutant, ser598ala of oat (avena sativa) phytochrome a (phya). the transgenic arabidopsis thaliana (phya-201 background) plants with this mutant phya showed hypersensitivity to light, suggesting that phytochr ... | 2004 | 15377754 |
| a classical arabinogalactan protein is essential for the initiation of female gametogenesis in arabidopsis. | classical arabinogalactan proteins (agps) are an abundant class of cell surface proteoglycans widely distributed in flowering plants. we have used a combination of enhancer detection tagging and rna interference (rnai)-induced posttrancriptional silencing to demonstrate that agp18, a gene encoding a classical arabinogalactan protein, is essential for female gametogenesis in arabidopsis thaliana. agp18 is expressed in cells that spatially and temporally define the sporophytic to gametophytic tran ... | 2004 | 15377758 |
| divergent roles of a pair of homologous jumonji/zinc-finger-class transcription factor proteins in the regulation of arabidopsis flowering time. | flowering in arabidopsis thaliana is controlled by multiple pathways, including the photoperiod pathway and the flowering locus c (flc)-dependent pathway. here, we report that a pair of related jumonji-class transcription factors, early flowering 6 (elf6) and relative of early flowering 6 (ref6), play divergent roles in the regulation of arabidopsis flowering. elf6 acts as a repressor in the photoperiod pathway, whereas ref6, which has the highest similarity to elf6, is an flc repressor. ectopic ... | 2004 | 15377760 |
| hanaba taranu is a gata transcription factor that regulates shoot apical meristem and flower development in arabidopsis. | we have isolated a new mutant, hanaba taranu (han), which affects both flower and shoot apical meristem (sam) development in arabidopsis thaliana. mutants have fused sepals and reduced organ numbers in all four whorls, especially in the 2nd (petal) and 3rd (stamen) whorls. han meristems can become flatter or smaller than in the wild type. han encodes a gata-3-like transcription factor with a single zinc finger domain. han is transcribed at the boundaries between the meristem and its newly initia ... | 2004 | 15367721 |
| silencing in arabidopsis t-dna transformants: the predominant role of a gene-specific rna sensing mechanism versus position effects. | pronounced variability of transgene expression and transgene silencing are commonly observed among independent plant lines transformed with the same construct. single-copy t-dna lines harboring reporter genes of various kind and number under the control of a strong promoter were established in arabidopsis thaliana for a comprehensive analysis of transgene expression. characterization of 132 independent transgenic lines revealed no case of silencing as a result of site of t-dna integration. below ... | 2004 | 15367719 |
| in vivo investigation of the transcription, processing, endonucleolytic activity, and functional relevance of the spatial distribution of a plant mirna. | we show, with mir171, that plant mirna genes are modular independent transcription units in which the fold-back pre-mirna is sufficient for mirna processing, and that the upstream region contains highly specific promoter elements. processing depends on flanking sequences within the mirna stem-loop precursor rather than the mirna sequence itself, and mutations affecting target pairing at the center and 5' but not 3' region of the mirna compromise its function in vivo. inactivation of the sde1 rna ... | 2004 | 15371337 |
| lwr1 and lwr2 are required for osmoregulation and osmotic adjustment in arabidopsis. | with the goal of identifying molecular components of the low-water-potential response, we have carried out a two-part selection and screening strategy to identify new arabidopsis mutants. using a system of polyethylene glycol-infused agar plates to impose a constant low-water-potential stress, putative mutants impaired in low-water-potential induction of the tomato (lycopersicon esculentum) le25 promoter were selected. these lines were then screened for altered accumulation of free pro. the seed ... | 2004 | 15347788 |
| light regulation of the arabidopsis respiratory chain. multiple discrete photoreceptor responses contribute to induction of type ii nad(p)h dehydrogenase genes. | controlled oxidation reactions catalyzed by the large, proton-pumping complexes of the respiratory chain generate an electrochemical gradient across the mitochondrial inner membrane that is harnessed for atp production. however, several alternative respiratory pathways in plants allow the maintenance of substrate oxidation while minimizing the production of atp. we have investigated the role of light in the regulation of these energy-dissipating pathways by transcriptional profiling of the alter ... | 2004 | 15333756 |
| frd3 controls iron localization in arabidopsis. | the frd3 mutant of arabidopsis exhibits constitutive expression of its iron uptake responses and is chlorotic. these phenotypes are consistent with defects either in iron deficiency signaling or in iron translocation and localization. here we present several experiments demonstrating that a functional frd3 gene is necessary for correct iron localization in both the root and shoot of arabidopsis plants. reciprocal grafting experiments with frd3 and wild-type arabidopsis plants reveal that the phe ... | 2004 | 15310833 |
| athkt1 facilitates na+ homeostasis and k+ nutrition in planta. | genetic and physiological data establish that arabidopsis athkt1 facilitates na(+) homeostasis in planta and by this function modulates k(+) nutrient status. mutations that disrupt athkt1 function suppress nacl sensitivity of sos1-1 and sos2-2, as well as of sos3-1 seedlings grown in vitro and plants grown in controlled environmental conditions. hkt1 suppression of sos3-1 nacl sensitivity is linked to higher na(+) content in the shoot and lower content of the ion in the root, reducing the na(+) ... | 2004 | 15347798 |
| related to ubiquitin 1 and 2 are redundant and essential and regulate vegetative growth, auxin signaling, and ethylene production in arabidopsis. | related to ubiquitin (rub)/nedd8 is a ubiquitin-like protein that covalently attaches to cullins, a subunit of the scf (for skp, cdc53p/cul1, and f-box protein) complex, an e3 ubiquitin ligase, and has been shown to be required for robust function of the complex. the effects of reducing protein levels for two rub proteins, rub1 and rub2, were characterized in arabidopsis thaliana. t-dna insertional null lines homozygous at a single rub-encoding locus were analyzed and found to have a wild-type p ... | 2004 | 15319484 |
| role of an atypical e2f transcription factor in the control of arabidopsis cell growth and differentiation. | the balance between cell proliferation and differentiation is crucial in multicellular organisms, where it is regulated by complex gene expression networks. this is particularly relevant in plants because organogenesis is a continuous postembryonic process. here, we investigate the function of arabidopsis thaliana e2ff, an atypical member of the e2f family of transcription factors, which acts independently of a dimerization partner. we have focused our analysis on roots and hypocotyls, organs wh ... | 2004 | 15308755 |
| napp and pirp encode subunits of a putative wave regulatory protein complex involved in plant cell morphogenesis. | the arp2/3 complex is an important regulator of actin nucleation and branching in eukaryotic organisms. all seven subunits of the arp2/3 complex have been identified in arabidopsis thaliana, and mutation of at least three of the subunits results in defects in epidermal cell expansion, including distorted trichomes. however, the mechanisms regulating the activity of the arp2/3 complex in plants are largely unknown. in mammalian cells, wave and wasp proteins are involved in activation of the arp2/ ... | 2004 | 15316111 |
| recessive-interfering mutations in the gibberellin signaling gene sleepy1 are rescued by overexpression of its homologue, sneezy. | this article reports the genetic interaction of two f-box genes, sleepy1 (sly1) and sneezy (sne), in arabidopsis thaliana gibberellin (ga) signaling. the sly1 gene encodes an f-box subunit of a skp1-cullin-f-box (scf) e3 ubiquitin ligase complex that positively regulates ga signaling. the sly1-2 and sly1-10 mutants have recessive, ga-insensitive phenotypes including delayed germination, dwarfism, reduced fertility, and overaccumulation of the della proteins rga (repressor of ga1-3), gai (ga-inse ... | 2004 | 15308775 |
| graft transmission of a floral stimulant derived from constans. | photoperiod in plants is perceived by leaves and in many species influences the transition to reproductive growth through long-distance signaling. constans (co) is implicated as a mediator between photoperiod perception and the transition to flowering in arabidopsis. to test the role of co in long-distance signaling, co was expressed from a promoter specific to the companion cells of the smallest veins of mature leaves. this expression in tissues at the inception of the phloem translocation stre ... | 2004 | 15299137 |
| the sensitive to freezing2 gene, required for freezing tolerance in arabidopsis thaliana, encodes a beta-glucosidase. | the sensitive to freezing2-1 (sfr2-1) mutation causes freezing sensitivity in arabidopsis thaliana. by mapping, transgenic complementation, and sequencing, sfr2-1 was revealed to be a mutation in gene at3g06510. a new knockout allele was obtained, and its identical freezing-sensitive phenotype confirmed that the sfr2 gene product is essential for freezing tolerance. transcription of sfr2 was observed to be constitutive rather than stress inducible and was distributed throughout most aerial tissu ... | 2004 | 15258268 |
| increased glutathione biosynthesis plays a role in nickel tolerance in thlaspi nickel hyperaccumulators. | worldwide more than 400 plant species are now known that hyperaccumulate various trace metals (cd, co, cu, mn, ni, and zn), metalloids (as) and nonmetals (se) in their shoots. of these, almost one-quarter are brassicaceae family members, including numerous thlaspi species that hyperaccumulate ni up to 3% of there shoot dry weight. we observed that concentrations of glutathione, cys, and o-acetyl-l-serine (oas), in shoot tissue, are strongly correlated with the ability to hyperaccumulate ni in va ... | 2004 | 15269333 |
| functional analysis of a 450-amino acid n-terminal fragment of phytochrome b in arabidopsis. | phytochrome, a major photoreceptor in plants, consists of two domains: the n-terminal photosensory domain and the c-terminal domain. recently, the 651-amino acid photosensory domain of phytochrome b (phyb) has been shown to act as a functional photoreceptor in the nucleus. the phytochrome (phy) domain, which is located at the c-terminal end of the photosensory domain, is required for the spectral integrity of phytochrome; however, little is known about the signal transduction activity of this do ... | 2004 | 15273294 |
| arabidopsis thaliana gln2-encoded glutamine synthetase is dual targeted to leaf mitochondria and chloroplasts. | in higher plants, photorespiratory gly oxidation in leaf mitochondria yields ammonium in large amounts. mitochondrial ammonium must somehow be recovered as glutamate in chloroplasts. as the first step in that recovery, we report glutamine synthetase (gs) activity in highly purified arabidopsis thaliana mitochondria isolated from light-adapted leaf tissue. leaf mitochondrial gs activity is further induced in response to either physiological co(2) limitation or transient darkness. historically, wh ... | 2004 | 15273293 |
| spermidine synthase genes are essential for survival of arabidopsis. | the cellular polyamines putrescine, spermidine, and spermine are ubiquitous in nature and have been implicated in a wide range of growth and developmental processes. there is little information, however, on mutant plants or animals defective in the synthesis of polyamines. the arabidopsis genome has two genes encoding spermidine synthase, spds1 and spds2. in this paper, we describe t-dna insertion mutants of both of these genes. while each mutant allele shows normal growth, spds1-1 spds2-1 doubl ... | 2004 | 15247389 |
| isolation and characterization of a terminal flower homolog and its correlation with juvenility in citrus. | terminal flower is a key regulator of floral timing in arabidopsis and other herbaceous species. a homolog of this gene, cstfl, was isolated from the hybrid perennial tree crop washington navel orange (citrus sinensis l. osbeck). the deduced amino acid sequence of cstfl was 65% identical to the arabidopsis tfl1 protein. wild-type arabidopsis plants ectopically expressing cstfl showed late-flowering phenotypes similar to those described for overexpression of arabidopsis tfl1. in addition, the 35s ... | 2004 | 15235113 |
| overexpression of osraa1 causes pleiotropic phenotypes in transgenic rice plants, including altered leaf, flower, and root development and root response to gravity. | there are very few root genes that have been described in rice as a monocotyledonous model plant so far. here, the osraa1 (oryza sativa root architecture associated 1) gene has been characterized molecularly. osraa1 encodes a 12.0-kd protein that has 58% homology to the atfpf1 (flowering promoting factor 1) in arabidopsis, which has not been reported as modulating root development yet. data of in situ hybridization and osraa1::gus transgenic plant showed that osraa1 expressed specifically in the ... | 2004 | 15247372 |
| a plant-specific subclass of c-terminal kinesins contains a conserved a-type cyclin-dependent kinase site implicated in folding and dimerization. | cyclin-dependent kinases (cdks) control cell cycle progression through timely coordinated phosphorylation events. two kinesin-like proteins that interact with cdka;1 were identified and designated kca1 and kca2. they are 81% identical and have a similar three-partite domain organization. the n-terminal domain contains an atp and microtubule-binding site typical for kinesin motors. a green fluorescent protein (gfp) fusion of the n-terminal domain of kca1 decorated microtubules in bright yellow-2 ... | 2004 | 15247388 |
| characterization of arabidopsis glutamine phosphoribosyl pyrophosphate amidotransferase-deficient mutants. | using a transgene-based screening, we previously isolated several arabidopsis mutants defective in protein import into chloroplasts. positional cloning of one of the loci, cia1, revealed that cia1 encodes gln phosphoribosyl pyrophosphate amidotransferase 2 (atase2), one of the three atase isozymes responsible for the first committed step of de novo purine biosynthesis. the cia1 mutant had normal green cotyledons but small and albino/pale-green mosaic leaves. adding amp, but not cytokinin or nadh ... | 2004 | 15266056 |
| the biosynthesis of d-galacturonate in plants. functional cloning and characterization of a membrane-anchored udp-d-glucuronate 4-epimerase from arabidopsis. | pectic cell wall polysaccharides owe their high negative charge to the presence of d-galacturonate, a monosaccharide that appears to be present only in plants and some prokaryotes. udp-d-galacturonate, the activated form of this sugar, is known to be formed by the 4-epimerization of udp-d-glucuronate; however, no coding regions for the epimerase catalyzing this reaction have previously been described in plants. to better understand the mechanisms by which precursors for pectin synthesis are prod ... | 2004 | 15247385 |
| jasmonate-insensitive1 encodes a myc transcription factor essential to discriminate between different jasmonate-regulated defense responses in arabidopsis. | in spite of the importance of jasmonates (jas) as plant growth and stress regulators, the molecular components of their signaling pathway remain largely unknown. by means of a genetic screen that exploits the cross talk between ethylene (et) and jas, we describe the identification of several new loci involved in ja signaling and the characterization and positional cloning of one of them, jasmonate-insensitive1 (jai1/jin1). jin1 encodes atmyc2, a nuclear-localized basic helix-loop-helix-leucine z ... | 2004 | 15208388 |
| arabidopsis radical-induced cell death1 belongs to the wwe protein-protein interaction domain protein family and modulates abscisic acid, ethylene, and methyl jasmonate responses. | experiments with several arabidopsis thaliana mutants have revealed a web of interactions between hormonal signaling. here, we show that the arabidopsis mutant radical-induced cell death1 (rcd1), although hypersensitive to apoplastic superoxide and ozone, is more resistant to chloroplastic superoxide formation, exhibits reduced sensitivity to abscisic acid, ethylene, and methyl jasmonate, and has altered expression of several hormonally regulated genes. furthermore, rcd1 has higher stomatal cond ... | 2004 | 15208394 |
| the calcium sensor calcineurin b-like 9 modulates abscisic acid sensitivity and biosynthesis in arabidopsis. | calcium plays a pivotal role in plant responses to several stimuli, including pathogens, abiotic stresses, and hormones. however, the molecular mechanisms underlying calcium functions are poorly understood. it is hypothesized that calcium serves as second messenger and, in many cases, requires intracellular protein sensors to transduce the signal further downstream in the pathways. the calcineurin b-like proteins (cbls) represent a unique family of calcium sensors in plant cells. here, we report ... | 2004 | 15208400 |
| a semidominant mutation in an arabidopsis mitogen-activated protein kinase phosphatase-like gene compromises cortical microtubule organization. | reversible protein phosphorylation regulates many cellular processes, including the dynamics and organization of the microtubule cytoskeleton, but the events mediating it are poorly understood. a semidominant phs1-1 allele of the arabidopsis thaliana propyzamide-hypersensitive 1 locus exhibits phenotypes indicative of compromised cortical microtubule functions, such as left-handed helical growth of seedling roots, defective anisotropic growth at low doses of microtubule-destabilizing drugs, enha ... | 2004 | 15208393 |
| overexpression of glutamine dumper1 leads to hypersecretion of glutamine from hydathodes of arabidopsis leaves. | secretion is a fundamental process providing plants with the means for disposal of solutes, improvement of nutrient acquisition, and attraction of other organisms. specific secretory organs, such as nectaries, hydathodes, and trichomes, use a combination of secretory and retrieval mechanisms, which are poorly understood at present. to study the mechanisms involved, an arabidopsis thaliana activation tagged mutant, glutamine dumper1 (gdu1), was identified that accumulates salt crystals at the hyd ... | 2004 | 15208395 |
| a conserved upstream open reading frame mediates sucrose-induced repression of translation. | sugars have been shown to regulate transcription of numerous genes in plants. sucrose controls translation of the group s basic region leucine zipper (bzip)-type transcription factor atb2/atbzip11 (rook et al., 1998a). this control requires the unusually long 5' untranslated region (utr) of the gene. point mutations and deletions of the 5'utr have uncovered the sequences involved. a highly conserved upstream open reading frame (uorf) coding for 42 amino acids is essential for the repression mech ... | 2004 | 15208401 |
| members of the toc159 import receptor family represent distinct pathways for protein targeting to plastids. | plastids represent a diverse group of organelles that perform essential metabolic and signaling functions within all plant cells. the differentiation of specific plastid types relies on the import of selective sets of proteins from among the approximately 2500 nucleus-encoded plastid proteins. the toc159 family of gtpases mediates the initial targeting of proteins to plastids. in arabidopsis thaliana, the toc159 family consists of four genes: attoc159, attoc132, attoc120, and attoc90. in vivo an ... | 2004 | 15090618 |
| evidence for acyl homoserine lactone signal production in bacteria associated with marine sponges. | we report for the first time the production of acyl homoserine lactones (ahls) by bacteria associated with marine sponges. given the involvement of ahls in bacterial colonization of many higher organisms, we speculate that such quorum sensing signals could play a part in interactions between sponges and the dense bacterial communities living within them. | 2004 | 15240326 |
| a probable na+(k+)/h+ exchanger on the chloroplast envelope functions in ph homeostasis and chloroplast development in arabidopsis thaliana. | electroneutral monovalent cation/proton antiport across the chloroplast envelope has been shown previously to have an important regulatory effect on stromal ph and thereby on photosynthetic carbon reduction. here we report that an arabidopsis nuclear gene, atchx23, encodes a putative na(+)(k(+))/h(+) exchanger and functions in the adjustment of ph in the cytosol and possibly in maintaining a high ph level in the chloroplast stroma. the atchx23 protein is localized in the chloroplast envelope. pl ... | 2004 | 15220473 |
| an arabidopsis homeodomain transcription factor gene, hos9, mediates cold tolerance through a cbf-independent pathway. | to investigate essential components mediating stress signaling in plants, we initiated a large-scale stress response screen using arabidopsis plants carrying the firefly luciferase reporter gene under the control of the stress-responsive rd29a promoter. here we report the identification and characterization of a mutant, hos9-1 (for high expression of osmotically responsive genes), in which the reporter construct was hyperactivated by low temperature, but not by abscisic acid or salinity stress. ... | 2004 | 15205481 |
| modulation of the polyamine biosynthetic pathway in transgenic rice confers tolerance to drought stress. | we have generated transgenic rice plants expressing the datura stramonium adc gene and investigated their response to drought stress. we monitored the steady-state mrna levels of genes involved in polyamine biosynthesis (datura adc, rice adc, and rice samdc) and polyamine levels. wild-type plants responded to the onset of drought stress by increasing endogenous putrescine levels, but this was insufficient to trigger the conversion of putrescine into spermidine and spermine (the agents that are b ... | 2004 | 15197268 |
| biochemical and molecular characterization of transgenic lotus japonicus plants constitutively over-expressing a cytosolic glutamine synthetase gene. | higher plants assimilate nitrogen in the form of ammonia through the concerted activity of glutamine synthetase (gs) and glutamate synthase (gogat). the gs enzyme is either located in the cytoplasm (gs1) or in the chloroplast (gs2). to understand how modulation of gs activity affects plant performance, lotus japonicus l. plants were transformed with an alfalfa gs1 gene driven by the camv 35s promoter. the transformants showed increased gs activity and an increase in gs1 polypeptide level in all ... | 2004 | 15197594 |
| a family of auxin-conjugate hydrolases that contributes to free indole-3-acetic acid levels during arabidopsis germination. | auxins are hormones important for numerous processes throughout plant growth and development. plants use several mechanisms to regulate levels of the auxin indole-3-acetic acid (iaa), including the formation and hydrolysis of amide-linked conjugates that act as storage or inactivation forms of the hormone. certain members of an arabidopsis amidohydrolase family hydrolyze these conjugates to free iaa in vitro. we examined amidohydrolase gene expression using northern and promoter-beta-glucuronida ... | 2004 | 15155875 |
| type-b response regulators display overlapping expression patterns in arabidopsis. | two-component signaling systems, involving his kinases, his-containing phosphotransfer proteins, and response regulators, have been implicated in plant responses to hormones and environmental factors. genomic analysis of arabidopsis supports the existence of 22 response regulators (arrs) that can be divided into at least two distinct groups designated type-a and type-b. phylogenetic analysis indicates that the type-b family is composed of one major and two minor subfamilies. the expression of th ... | 2004 | 15173562 |
| expression of the isochrysis c18-delta9 polyunsaturated fatty acid specific elongase component alters arabidopsis glycerolipid profiles. | a cdna isolated from the prymnesiophyte micro-alga isochrysis galbana, designated igase1, encodes a fatty acid elongating component that is specific for linoleic acid (c18:2n-6) and alpha-linolenic acid (c18:3n-3). constitutive expression of igase1 in arabidopsis resulted in the accumulation of eicosadienoic acid (eda; c20:2n-6) and eicosatrienoic acid (etra; c20:3n-3) in all tissues examined, with no visible effects on plant morphology. positional analysis of the various lipid classes indicated ... | 2004 | 15173563 |
| centrin2 modulates homologous recombination and nucleotide excision repair in arabidopsis. | a genetic screen of a population of arabidopsis thaliana lines exhibiting enhanced somatic homologous recombination yielded a mutant affected in expression of a gene encoding a caltractin-like protein (centrin). the hyperrecombinogenic phenotype could be reproduced using rna interference (rnai) technology. both the original mutant and the rnai plants exhibited a moderate uv-c sensitivity as well as a reduced efficiency of in vitro repair of uv-damaged dna. transcription profiling of the mutant s ... | 2004 | 15155891 |