| the structure and regulation of homeologous tobacco endochitinase genes of nicotiana sylvestris and n. tomentosiformis origin. | the fungicidal class i chitinases are believed to be important in the induced defense response of plants. we isolated and partially characterized genomic clones representing two members, chn14 and chn50, of the gene subfamily encoding these enzymes in nicotiana tabacum l. cv. havana 425. the coding sequences of genes chn14, chn50, and chn48, which was cloned earlier, are identical at 79-95% of the positions. tobacco is an amphidiploid species derived from ancestors most closely related to the pr ... | 1992 | 1588915 |
| the function of vacuolar beta-1,3-glucanase investigated by antisense transformation. susceptibility of transgenic nicotiana sylvestris plants to cercospora nicotianae infection. | vacuolar class i beta-1,3-glucanases (ec 3.2.1.39) are believed to be important in the induced defense reaction of plants to fungal infection. we used antisense transformation to test this hypothesis and to identify other possible physiological functions of this enzyme. nicotiana sylvestris plants were transformed with antisense constructions containing the region from position 27 to 608 of the coding sequence of the basic, vacuolar beta-1,3-glucanase gene gla of tobacco regulated by cauliflower ... | 1992 | 1643283 |
| high-level expression of a tobacco chitinase gene in nicotiana sylvestris. susceptibility of transgenic plants to cercospora nicotianae infection. | endochitinases (e.c.3.2.14, chitinase) are believed to be important in the biochemical defense of plants against chitin-containing fungal pathogens. we introduced a gene for class i (basic) tobacco chitinase regulated by cauliflower mosaic virus 35s-rna expression signals into nicotiana sylvestris. the gene was expressed to give mature, enzymatically active chitinase targeted to the intracellular compartment of leaves. most transformants accumulated extremely high levels of chitinase-up to 120-f ... | 1991 | 1888892 |
| increased disease susceptibility of transgenic tobacco plants with suppressed levels of preformed phenylpropanoid products. | it has been proposed that natural products synthesized by plants contribute to their resistance to pests and pathogens. we show here that transgenic tobacco plants with suppressed levels of the phenylpropanoid biosynthetic enzyme phenylalanine ammonia-lyase (l-phenylalanine ammonia-lyase, ec 4.3.1.5) and correspondingly low levels of chlorogenic acid, the major soluble leaf phenylpropanoid product, exhibit more rapid and extensive lesion development than wild-type plants after infection by the v ... | 1994 | 8052663 |
| isolation, sequence, and characterization of the cercospora nicotianae phytoene dehydrogenase gene. | we have cloned and sequenced the cercospora nicotianae gene for the carotenoid biosynthetic enzyme phytoene dehydrogenase. analysis of the derived amino acid sequence revealed it has greater than 50% identity with its counterpart in neurospora crassa and approximately 30% identity with prokaryotic phytoene dehydrogenases and is related, but more distantly, to phytoene dehydrogenases from plants and cyanobacteria. our analysis confirms that phytoene dehydrogenase proteins fall into two groups: th ... | 1994 | 8085820 |
| pathogenesis-related functions of plant beta-1,3-glucanases investigated by antisense transformation--a review. | plant beta-1,3-glucanases (beta glu) have been implicated in several physiological and developmental processes, e.g., cell division, microsporogenesis, pollen germination, fertilization and seed germination. these enzymes, particularly the antifungal class-i vacuolar isoforms, are also believed to be part of the defences of plants against fungal infection. the function of beta glu in tobacco and nicotiana sylvestris has been investigated by antisense transformation. transformation with gla, the ... | 1996 | 8955634 |
| a peroxidase gene promoter induced by phytopathogens and methyl jasmonate in transgenic plants. | the expression of two closely related peroxidase isogenes, shpx6a and shpx6b, of the legume stylosanthes humilis was studied using isogene-specific reverse transcriptase pcr techniques. results indicated that transcripts of both genes were rapidly induced following inoculation with the fungal pathogen colletotrichum gloeosporioides, wounding and treatment with the defense regulator methyl jasmonate (meja). in contrast treatment of leaves of s. humilis with abscisic acid (aba) and salicylic acid ... | 1997 | 9100378 |
| functional characterization of sor1, a gene required for resistance to photosensitizing toxins in the fungus cercospora nicotianae. | the cercospora nicotianae sor1 gene is required for resistance to singlet oxygen-generating photosensitizers. sor1 was characterized in the wild-type and in five photosensitizer-sensitive mutant strains which are complemented to photosensitizer resistance by transformation with sor1. sequence analysis determined that three of the mutants contain sor1 copies with mutations encoding substitutions in the protein-coding sequence; however, two other mutants had wild-type sor1 protein and promoter seq ... | 1999 | 9933360 |
| a highly conserved sequence is a novel gene involved in de novo vitamin b6 biosynthesis. | the cercospora nicotianae sor1 (singlet oxygen resistance) gene was identified previously as a gene involved in resistance of this fungus to singlet-oxygen-generating phototoxins. although homologues to sor1 occur in organisms in four kingdoms and encode one of the most highly conserved proteins yet identified, the precise function of this protein has, until now, remained unknown. we show that sor1 is essential in pyridoxine (vitamin b6) synthesis in c. nicotianae and aspergillus flavus, althoug ... | 1999 | 10430950 |
| a novel gene required for cercosporin toxin resistance in the fungus cercospora nicotianae. | cercosporin, a photosensitizing perylenequinone toxin produced by the plant pathogenic cercospora fungi, generates the highly toxic singlet oxygen (1o2) upon exposure to light. cercosporin shows broad toxicity against a wide range of organisms, including bacteria, fungi, plants, and animals; however, cercospora fungi are resistant to its effects. a novel gene, crg1 (cercosporin-resistance gene) was isolated from a wild-type strain of c. nicotianae by genetic complementation of a c. nicotianae mu ... | 1999 | 10517336 |
| vitamin b6 (pyridoxine) and its derivatives are efficient singlet oxygen quenchers and potential fungal antioxidants. | vitamin b6 (pyridoxine, 1) and its derivatives: pyridoxal (2), pyridoxal 5-phosphate (3) and pyridoxamine (4) are important natural compounds involved in numerous biological functions. pyridoxine appears to play a role in the resistance of the filamentous fungus cercospora nicotianae to its own abundantly produced strong photosensitizer of singlet molecular oxygen (1o2), cercosporin. we measured the rate constants (kq) for the quenching of 1o2 phosphorescence by 1-4 in d2o. the respective total ... | 2000 | 10687384 |
| phylogenetic analyses and comparative genomics of vitamin b6 (pyridoxine) and pyridoxal phosphate biosynthesis pathways. | vitamin b6 in its active form pyridoxal phosphate is an essential coenzyme of many diverse enzymes. biochemistry, enzymology and genetics of de novo vitamin b6 biosynthesis have been primarily investigated in escherichia coli. database searches revealed that the key enzymes involved in ring closure of the aromatic pyridoxin ring (pdxa; pdxj) are present mainly in genomes of bacteria constituting the gamma subdivision of proteobacteria. the distribution of dxs, a transketolase-like enzyme involve ... | 2001 | 11200221 |
| analysis of the pdx-1 (snz-1/sno-1) region of the neurospora crassa genome: correlation of pyridoxine-requiring phenotypes with mutations in two structural genes. | we report the analysis of a 36-kbp region of the neurospora crassa genome, which contains homologs of two closely linked stationary phase genes, snz1 and sno1, from saccharomyces cerevisiae. homologs of snz1 encode extremely highly conserved proteins that have been implicated in pyridoxine (vitamin b6) metabolism in the filamentous fungi cercospora nicotianae and in aspergillus nidulans. in n. crassa, snz and sno homologs map to the region occupied by pdx-1 (pyridoxine requiring), a gene that ha ... | 2001 | 11238395 |
| isolation of pdx2, a second novel gene in the pyridoxine biosynthesis pathway of eukaryotes, archaebacteria, and a subset of eubacteria. | in this paper we describe the isolation of a second gene in the newly identified pyridoxine biosynthesis pathway of archaebacteria, some eubacteria, fungi, and plants. although pyridoxine biosynthesis has been thoroughly examined in escherichia coli, recent characterization of the cercospora nicotianae biosynthesis gene pdx1 led to the discovery that most organisms contain a pyridoxine synthesis gene not found in e. coli. pdx2 was isolated by a degenerate primer strategy based on conserved seque ... | 2001 | 11344146 |
| functional expression and cellular localization of cercosporin-resistance proteins fused with the gfp in cercospora nicotianae. | the cercospora nicotianae pdx1 and crg1 genes were previously identified as genes required for resistance to the singlet oxygen ((1)o(2))-generating toxin cercosporin. the pdx1 gene has subsequently been shown to be required for pyridoxine biosynthesis, but both the precise biochemical function of the pdx1 protein and the function of the crg1 protein remain undefined, as both sequences lack defined enzymatic domains or cofactor-binding sites. the gfp gene encoding green fluorescent protein was t ... | 2002 | 12111097 |
| a r2r3-myb gene, atmyb30, acts as a positive regulator of the hypersensitive cell death program in plants in response to pathogen attack. | hypersensitive response (hr) is a programmed cell death that is commonly associated with disease resistance in plants. among the different hr-related early induced genes, the atmyb30 gene is specifically, rapidly, and transiently expressed during incompatible interactions between arabidopsis and bacterial pathogens. its expression was also shown to be deregulated in arabidopsis mutants affected in the control of cell death initiation. here, we demonstrate that overexpression in arabidopsis and t ... | 2002 | 12119395 |
| constitutive expression of a celery mannitol dehydrogenase in tobacco enhances resistance to the mannitol-secreting fungal pathogen alternaria alternata. | our previous observation that host plant extracts induce production and secretion of mannitol in the tobacco pathogen alternaria alternata suggested that, like their animal counterparts, plant pathogenic fungi might produce the reactive oxygen quencher mannitol as a means of suppressing reactive oxygen-mediated plant defenses. the concurrent discovery that pathogen attack induced mannitol dehydrogenase (mtd) expression in the non-mannitol-containing host tobacco suggested that plants, unlike ani ... | 2002 | 12366799 |
| involvement of calcium/calmodulin signaling in cercosporin toxin biosynthesis by cercospora nicotianae. | cercosporin is a non-host-selective, perylenequinone toxin produced by many phytopathogenic cercospora species. the involvement of ca(2+)/calmodulin (cam) signaling in cercosporin biosynthesis was investigated by using pharmacological inhibitors. the results suggest that maintaining endogenous ca(2+) homeostasis is required for cercosporin biosynthesis in cercospora nicotianae. the addition of excess ca(2+) to the medium slightly increased fungal growth but resulted in a reduction in cercosporin ... | 2003 | 12571046 |
| the crg1 gene required for resistance to the singlet oxygen-generating cercosporin toxin in cercospora nicotianae encodes a putative fungal transcription factor. | the cercospora nicotianae crg1 gene is involved in cellular resistance to the perylenequinone toxin, cercosporin, that generates highly toxic singlet oxygen upon exposure to light. the entire open reading frame (orf) of crg1 was isolated and sequenced. the gene contains an orf of 1950bp including a 65-bp intron. the predicted 650 amino acid crg1 protein contains a cys(6)zn(2) binuclear cluster dna-binding motif with homology to various fungal regulatory proteins, indicating that crg1 may act fun ... | 2003 | 12604346 |
| expression of the cercosporin toxin resistance gene ( crg1) as a dicistronic mrna in the filamentous fungus cercospora nicotianae. | the crg1 gene in cercospora nicotianae encodes a transcription factor and is required for cercosporin toxin resistance and production. cloning and sequencing of the downstream region of the crg1 gene led to the discovery of an adjacent gene ( put1) encoding a putative uracil transporter. expression of crg1 and put1 as assessed by northern analysis indicated that, in addition to the expected monocistronic mrnas (2.6 kb and 2.0 kb, respectively), a common 4.5-kb mrna could be identified, using eit ... | 2003 | 12802507 |
| cercosporin-deficient mutants by plasmid tagging in the asexual fungus cercospora nicotianae. | we have successfully adapted plasmid insertion and restriction enzyme-mediated integration (remi) to produce cercosporin toxin-deficient mutants in the asexual phytopathogenic fungus cercospora nicotianae. the use of pre-linearized plasmid or restriction enzymes in the transformation procedure significantly decreased the transformation frequency, but promoted a complicated and undefined mode of plasmid integration that leads to mutations in the c. nicotianae genome. vector dna generally integrat ... | 2003 | 12937958 |
| phenylpropanoid compounds and disease resistance in transgenic tobacco with altered expression of l-phenylalanine ammonia-lyase. | tobacco plants over-expressing l-phenylalanine ammonia-lyase (pal(+)) produce high levels of chlorogenic acid (cga) and exhibit markedly reduced susceptibility to infection with the fungal pathogen cercospora nicotianae, although their resistance to tobacco mosaic virus (tmv) is unchanged. levels of the signal molecule salicylic acid (sa) were similar in uninfected pal(+) and control plants and also following tmv infection. in crosses of pal(+) tobacco with tobacco harboring the bacterial nahg s ... | 2003 | 12946414 |
| characterization of the products of the genes sno1 and snz1 involved in pyridoxine synthesis in saccharomyces cerevisiae. | genes sno1 and snz1 are saccharomyces cerevisiae homologues of pdx2 and pdx1 which participate in pyridoxine synthesis in the fungus cercospora nicotianae. in order to clarify their function, the two genes sno1 and snz1 were expressed in escherichia coli either individually or simultaneously and with or without a his-tag. when expressed simultaneously, the two protein products formed a complex and showed glutaminase activity. when purified to homogeneity, the complex exhibited a specific activit ... | 2004 | 14764090 |
| tobacco transgenic for the flax rust resistance gene l expresses allele-specific activation of defense responses. | tobacco was transformed with three different alleles (l2, l6, and l10) of the flax rust resistance gene l, a member of the toll interleukin-1 receptor, nucleotide-binding site, leucine-rich repeat (tir-nbs-lrr) class of plant disease resistance genes. l6 transgenics had a stunted phenotype, expressed several defense response genes constitutively, and had increased resistance to the fungus cercospora nicotianae and the oomycete phytophthora parasitica pv. nicotianae. l2 and l10 transgenics, with ... | 2004 | 14964536 |
| a highly conserved gene for vitamin b biosynthesis may have consequences for stress and hormone responses in plants. | pyridoxine (vitamin b(6)) is not only an essential cofactor in amino acid biosynthesis but has recently been added to the list of potent antioxidants found in plants (bilski et al., 71: 129-134, 2000). herein the cloning of a gene (pvpdx1) from phaseolus vulgaris that has a high degree of similarity to pdx1 from cercospora nicotianae is reported. in c. nicotianae, pdx1 is involved in the biosynthesis of pyridoxine as null mutants exhibit pyridoxine auxotrophy (ehrenshaft et al., proc natl acad s ... | 2004 | 15086812 |
| functional complementation between the pdx1 vitamin b6 biosynthetic gene of cercospora nicotianae and pdxj of escherichia coli. | the pathway for de novo vitamin b(6) biosynthesis has been characterized in escherichia coli, however plants, fungi, archaebacteria, and most bacteria utilize an alternative pathway. two unique genes of the alternative pathway, pdx1 and pdx2, have been described. pdx2 encodes a glutaminase, however the enzymatic function of the product encoded by pdx1 is not known. we conducted reciprocal transformation experiments to determine if there was functional homology between the e. coli pdxa and pdxj g ... | 2004 | 15094056 |
| the ctb1 gene encoding a fungal polyketide synthase is required for cercosporin biosynthesis and fungal virulence of cercospora nicotianae. | cercosporin is a light-activated, non-host-selective toxin produced by many cercospora fungal species. in this study, a polyketide synthase gene (ctb1) was functionally identified and molecularly characterized to play a key role in cercosporin biosynthesis by cercospora nicotianae. we also provide conclusive evidence to confirm the crucial role of cercosporin in fungal pathogenesis. ctb1 encoded a polypeptide with a deduced length of 2,196 amino acids containing a keto synthase (ks), an acyltran ... | 2005 | 15915645 |
| expression of the cercosporin transporter, cfp, in tobacco reduces frog-eye lesion size. | the cercosporin major facilitator superfamily (mfs) transporter, cfp, under the control of the camv 35s promoter, was introduced into the xanthi cultivar of tobacco by agrobacterium-mediated transformation. cfp(+) transgenic plants were physically indistinguishable from non-transgenic xanthi and progressed normally through growth to seed set. accumulation of cfp in the leaf membrane fraction of cfp(+ )transgenic plants was associated with decreased cercosporin phytotoxicity. frog-eye leaf lesion ... | 2005 | 16245172 |
| the cercospora nicotianae gene encoding dual o-methyltransferase and fad-dependent monooxygenase domains mediates cercosporin toxin biosynthesis. | cercosporin, a photo-activated, non-host-selective phytotoxin produced by many species of the plant pathogenic fungus cercospora, causes peroxidation of plant cell membranes by generating reactive oxygen species and is an important virulence determinant. here we report a new gene, ctb3 that is involved in cercosporin biosynthesis in cercospora nicotianae. ctb3 is adjacent to a previously identified ctb1 encoding a polyketide synthase which is also required for cercosporin production. ctb3 contai ... | 2007 | 17074519 |
| deletion of a mfs transporter-like gene in cercospora nicotianae reduces cercosporin toxin accumulation and fungal virulence. | many phytopathogenic cercospora species produce a host-nonselective polyketide toxin, called cercosporin, whose toxicity exclusively relies on the generation of reactive oxygen species. here, we describe a cercospora nicotianae ctb4 gene that encodes a putative membrane transporter and provide genetic evidence to support its role in cercosporin accumulation. the predicted ctb4 polypeptide has 12 transmembrane segments with four conserved motifs and has considerable similarity to a wide range of ... | 2007 | 17250832 |
| molecular analysis of the cercosporin biosynthetic gene cluster in cercospora nicotianae. | we describe a core gene cluster, comprised of eight genes (designated ctb1-8), and associated with cercosporin toxin production in cercospora nicotianae. sequence analysis identified 10 putative open reading frames (orfs) flanking the previously characterized ctb1 and ctb3 genes that encode, respectively, the polyketide synthase and a dual methyltransferase/monooxygenase required for cercosporin production. expression of eight of the genes was co-ordinately induced under cercosporin-producing co ... | 2007 | 17462021 |
| functional characterization of three genes encoding putative oxidoreductases required for cercosporin toxin biosynthesis in the fungus cercospora nicotianae. | cercosporin is a non-host-selective, photoactivated polyketide toxin produced by many phytopathogenic cercospora species, which plays a crucial role during pathogenesis on host plants. upon illumination, cercosporin converts oxygen molecules to toxic superoxide and singlet oxygen that damage various cellular components and induce lipid peroxidation and electrolyte leakage. three genes (ctb5, ctb6 and ctb7) encoding putative fad/fmn- or nadph-dependent oxidoreductases in the cercosporin toxin bio ... | 2007 | 17660442 |
| identification of genes differentially expressed in the phytopathogenic fungus cercospora nicotianae between cercosporin toxin-resistant and -susceptible strains. | plant pathogens from the genus cercospora produce cercosporin, a photoactivated fungal toxin that generates toxic reactive oxygen species. mechanisms governing toxin auto-resistance in cercospora spp. are poorly understood. in this work, suppressive subtractive hybridization was used to identify genes differentially expressed between the cercosporin-resistant wild-type (wt) cercospora nicotianae and a sensitive strain lacking a transcription factor (crg1) that regulates resistance. out of 338 se ... | 2007 | 17850326 |
| production of cercosporin toxin by the phytopathogenic cercospora fungi is affected by diverse environmental signals. | cercosporin is a polyketide phytotoxin produced by many phytopathogenic cercospora spp. we investigated environmental signals that have elaborate control of cercosporin production. light is the most critical factor for cercosporin production. cercospora nicotianae accumulated substantial quantities of cercosporin only when grown on a particular potato dextrose agar under light but produced little cercosporin on other brands of potato dextrose agar or media with defined ingredients. in addition t ... | 2008 | 18388998 |
| ethylene-insensitive tobacco shows differentially altered susceptibility to different pathogens. | abstract transgenic tobacco plants (tetr) expressing the mutant etr1-1 gene from arabidopsis thaliana are insensitive to ethylene and develop symptoms of wilting and stem rot when grown in nonautoclaved soil. several isolates of fusarium, thielaviopsis, and pythium were recovered from stems of diseased tetr plants. inoculation with each of these isolates of 6-week-old plants growing in autoclaved soil caused disease in tetr plants but not in nontransformed plants. also, when 2-week-old seedlings ... | 2003 | 18943162 |
| the abc transporter atr1 is necessary for efflux of the toxin cercosporin in the fungus cercospora nicotianae. | the cercospora nicotianae mutant deficient for the crg1 transcription factor has marked reductions in both resistance and biosynthesis of the toxin cercosporin. we cloned and sequenced full-length copies of two genes, atr1 and cncfp, previously identified from a subtractive library between the wild type (wt) and a crg1 mutant. atr1 is an abc transporter gene and has an open reading frame (orf) of 4368bp with one intron. cncfp encodes a mfs transporter with homology to cercospora kikuchii cfp, pr ... | 2009 | 19095071 |
| gene-specific disruption in the filamentous fungus cercospora nicotianae using a split-marker approach. | to determine if dna configuration, gene locus, and flanking sequences will affect homologous recombination in the phytopathogenic fungus cercospora nicotianae, we evaluated and compared disruption efficiency targeting four cercosporin toxin biosynthetic genes encoding a polyketide synthase (ctb1), a monooxygenase/o-methyltransferase (ctb3), a nadph-dependent oxidoreductase (ctb5), and a fad/fmn-dependent oxidoreductase (ctb7). transformation of c. nicotianae using a circular plasmid resulted in ... | 2009 | 19506835 |
| expression of the shpx2 peroxidase gene of stylosanthes humilis in transgenic tobacco leads to enhanced resistance to phytophthora parasitica pv. nicotianae and cercospora nicotianae. | abstract previous research indicated that the constitutive expression of a pathogen-inducible peroxidase gene (shpx6a) from stylosanthes humilis in transgenic plants resulted in enhanced resistance to fungal pathogens ( kazan, k., goulter, k.c., way, h.m. and manners, j.m. (1998) expression of a pathogenesis-related peroxidase of stylosanthes humilis in transgenic tobacco and canola and its effect on disease development. plant sci. 136, 207-217). we have now investigated another pathogen-inducib ... | 2000 | 20572969 |