The Experts below are selected from a list of 459 Experts worldwide ranked by ideXlab platform
Margaret E. Daub - One of the best experts on this subject based on the ideXlab platform.
-
engineering Cercospora disease resistance via expression of Cercospora nicotianae cercosporin resistance genes and silencing of cercosporin production in tobacco
PLOS ONE, 2020Co-Authors: Elizabeth Thomas, Aydin Beseli, Roslyn D Noar, Sonia Herrero, Nafisa Gomaa, Jeff Gillikin, Margaret E. DaubAbstract:Fungi in the genus Cercospora cause crop losses world-wide on many crop species. The wide host range and success of these pathogens has been attributed to the production of a photoactivated toxin, cercosporin. We engineered tobacco for resistance to Cercospora nicotianae utilizing two strategies: 1) transformation with cercosporin autoresistance genes isolated from the fungus, and 2) transformation with constructs to silence the production of cercosporin during disease development. Three C. nicotianae cercosporin autoresistance genes were tested: ATR1 and CFP, encoding an ABC and an MFS transporter, respectively, and 71cR, which encodes a hypothetical protein. Resistance to the pathogen was identified in transgenic lines expressing ATR1 and 71cR, but not in lines transformed with CFP. Silencing of the CTB1 polyketide synthase and to a lesser extent the CTB8 pathway regulator in the cercosporin biosynthetic pathway also led to the recovery of resistant lines. All lines tested expressed the transgenes, and a direct correlation between the level of transgene expression and disease resistance was not identified in any line. Resistance was also not correlated with the degree of silencing in the CTB1 and CTB8 silenced lines. We conclude that expression of fungal cercosporin autoresistance genes as well as silencing of the cercosporin pathway are both effective strategies for engineering resistance to Cercospora diseases where cercosporin plays a critical role.
-
The Toxin Cercosporin is a Virulence Factor for Infection of Coffee by Cercospora coffeicola
2019Co-Authors: A. G. C. Souza, Sonia Herrero, Margaret E. DaubAbstract:ABSTRACT Brown eye spot, caused by Cercospora coffeicola, causes significant losses in both quality and quantity of coffee production. As many Cercospora spp. produce the photoactivated toxin cercosporin, this study aimed to determine the role of cercosporin in C. coffeicola pathogenesis by creating disruption mutants unable to produce the toxin. Six C. coffeicola isolates from Brazilian fields, representing organic and conventional production systems in the Minas Gerais state, were evaluated for their ability to produce cercosporin in vitro. Toxin production varied among isolates, ranging from 3.5 – 25.3 µM/ 5 mm mycelial plug; production was undetectable in one isolate. The C. coffeicola homolog of the polyketide synthase gene (CTB1) involved in cercosporin production was amplified using a degenerate primer strategy. The 7044 nt ccCTB1 gene sequence was 90.3% identical to the cnCTB1 gene in Cercospora nicotianae and encoded a putative protein of 2196 amino acids with 98.2% similarity and 97.5% identity to its counterpart in C. nicotianae. Transformation of two isolates of C. coffeicola with a CTB1 disruption construct resulted in the recovery of six ctb1 disruption mutants. All of the ctb1 disruptants were deficient in cercosporin production. Disruption mutants did not differ significantly from the wild type for either growth or sporulation, but were significantly altered in virulence on coffee. As compared to wild type, time to lesion development was significantly increased and numbers of lesions were significantly decreased in coffee plants inoculated with ctb1 disruption mutants. These results show that cercosporin toxin is a virulence factor for C. coffeicola infection of coffee.
-
Phylogenetic analysis of PKS8-1.
2019Co-Authors: Roslyn D Noar, Elizabeth Thomas, Margaret E. DaubAbstract:RAxML was used to create a maximum likelihood phylogenetic tree of PKS protein sequences, using the PKS sequences described previously [18] and others including the monodictyphenone-producing MdpG from A. nidulans, the cladofulvin-producing ClaG from C. fulvum, and the PKS8-1 homolog sequences identified from P. musae and P. eumusae. The clade containing PKS8-1, its P. musae and P. eumusae homologs, the monodictyphenone-producing PKS from A. nidulans, and the cladofulvin-producing PKS from C. fulvum is shown with a red box. Bootstrap values are indicated on the tree, and the scale bar indicates substitutions per site. An = Aspergillus nidulans; Ap = Aspergillus parasiticus; As = Alternaria solani; At = Aspergillus terreus; Bm = Bipolaris maydis; Bo = Bipolaris oryzae; Cf = Cladosporium fulvum; Cg = Colletotrichum graminicola; Cn = Cercospora nicotianae; Czm = Cercospora zeae-maydis; Ed = Exophiala dermatitidis; Fm = Fusarium moniliforme; Fv = Fusarium verticillioides; Gl = Glarea lozoyensis; Pc = Penicillium citrinum; Pg = Penicillium griseofulvum; Pe = PseudoCercospora eumusae; Pf = PseudoCercospora fijiensis; Pm = PseudoCercospora musae.
-
Maximum likelihood phylogenetic tree of PKS protein sequences.
2016Co-Authors: Roslyn D Noar, Margaret E. DaubAbstract:RAxML was used to generate a maximum likelihood phylogenetic tree of M. fijiensis PKS protein sequences as well as protein sequences from well-characterized PKS genes from other species. Products of each well-characterized PKS enzyme are indicated on the tree, along with abbreviations for species names. Numbers on branches indicate bootstrap support for the clade. Scale bar of branch length indicates substitutions per site. Number of iterations catalyzed by each PKS enzyme is indicated next to the name of the polyketide product of the PKS, in a matching color font. Orange = 3 ketide subunits; Brown = 5 ketide subunits; Red = 7 ketide subunits; Blue = 8 ketide subunits; Purple = 9 ketide subunits; Green = 10 ketide subunits; Pink = 20 ketide subunits. An = Aspergillus nidulans; Ap = Aspergillus parasiticus; As = Alternaria solani; At = Aspergillus terreus; Bm = Bipolaris maydis; Bo = Bipolaris oryzae; Cg = Colletotrichum graminicola; Cn = Cercospora nicotianae; Czm = Cercospora zeae-maydis; Ed = Exophiala dermatitidis; Fv = Fusarium verticillioides; Gl = Glarea lozoyensis; Pc = Penicillium citrinum; Pg = Penicillium griseofulvum. Accession numbers for each PKS sequence are available in S1 Table.
-
Membrane transporters in self resistance of Cercospora nicotianae to the photoactivated toxin cercosporin
Current Genetics, 2015Co-Authors: Aydin Beseli, Sonia Herrero, Alongkorn Amnuaykanjanasin, Elizabeth Thomas, Margaret E. DaubAbstract:The goal of this work is to characterize membrane transporter genes in Cercospora fungi required for autoresistance to the photoactivated, active-oxygen-generating toxin cercosporin they produce for infection of host plants. Previous studies implicated a role for diverse membrane transporters in cercosporin resistance. In this study, transporters identified in a subtractive cDNA library between a Cercospora nicotianae wild type and a cercosporin-sensitive mutant were characterized, including two ABC transporters (CnATR2, CnATR3), an MFS transporter (CnMFS2), a uracil transporter, and a zinc transport protein. Phylogenetic analysis showed that only CnATR3 clustered with transporters previously characterized to be involved in cercosporin resistance. Quantitative RT-PCR analysis of gene expression under conditions of cercosporin toxicity, however, showed that only CnATR2 was upregulated, thus this gene was selected for further characterization. Transformation and expression of CnATR2 in the cercosporin-sensitive fungus Neurospora crassa significantly increased cercosporin resistance. Targeted gene disruption of CnATR2 in the wild type C. nicotianae , however, did not decrease resistance. Expression analysis of other transporters in the cnatr2 mutant under conditions of cercosporin toxicity showed significant upregulation of the cercosporin facilitator protein gene ( CFP ), encoding an MFS transporter previously characterized as playing an important role in cercosporin autoresistance in Cercospora species. We conclude that cercosporin autoresistance in Cercospora is mediated by multiple genes, and that the fungus compensates for mutations by up-regulation of other resistance genes. CnATR2 may be a useful gene, alone or in addition to other known resistance genes, for engineering Cercospora resistance in crop plants.
Kuangren Chung - One of the best experts on this subject based on the ideXlab platform.
-
gene specific disruption in the filamentous fungus Cercospora nicotianae using a split marker approach
Archives of Microbiology, 2009Co-Authors: Kuangren ChungAbstract: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 low disruption frequency. The use of endonucleases or a selectable marker DNA fragment flanked by homologous sequence either at one end or at both ends in the transformation procedures, increased disruption efficiency in some but not all CTB genes. A split-marker approach, using two DNA fragments overlapping within the selectable marker, increased the frequency of targeted gene disruption and homologous integration as high as 50%, depending on the target gene and on the length of homologous DNA sequence flanking the selectable marker. The results indicate that the split-marker approach favorably decreased ectopic integration and thus, greatly facilitated targeted gene disruption in this important fungal pathogen.
-
molecular analysis of the cercosporin biosynthetic gene cluster in Cercospora nicotianae
Molecular Microbiology, 2007Co-Authors: Huiqin Chen, Margret E Daub, Kuangren ChungAbstract:Summary 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 conditions and was regulated by the Zn(II)Cys6 transcriptional activator, CTB8. Expression of the genes, affected by nitrogen and carbon sources and pH, was also controlled by another transcription activator, CRG1, previously shown to regulate cercosporin production and resistance. Disruption of the CTB2 gene encoding a methyltransferase or the CTB8 gene yielded mutants that were completely defective in cercosporin production and inhibitory expression of the other CTB cluster genes. Similar ‘feedback’ transcriptional inhibition was observed when the CTB1, or CTB3 but not CTB4 gene was inactivated. Expression of four ORFs located on the two distal ends of the cluster did not correlate with cercosporin biosynthesis and did not show regulation by CTB8, suggesting that the biosynthetic cluster was limited to CTB1–8. A biosynthetic pathway and a regulatory network leading to cercosporin formation are proposed.
-
the Cercospora nicotianae gene encoding dual o methyltransferase and fad dependent monooxygenase domains mediates cercosporin toxin biosynthesis
Fungal Genetics and Biology, 2007Co-Authors: Katherine L Dekkers, Vivek S Gowda, Huiling Liao, Peter P Ueng, Kuangren ChungAbstract:Abstract 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 contains a putative O-methyltransferase domain in the N-terminus and a putative flavin adenine dinucleotide (FAD)-dependent monooxygenase domain in the C-terminus. The N-terminal amino acid sequence also is similar to that of the transcription enhancer AFLS (formerly AFLJ) involved in aflatoxin biosynthesis. Expression of CTB3 was differentially regulated by light, medium, nitrogen and carbon sources and pH. Disruption of the N- or C-terminus of CTB3 yielded mutants that failed to accumulate the CTB3 transcript and cercosporin. The Δctb3 disruptants produced a yellow pigment that is not toxic to tobacco suspension cells. Production of cercosporin in a Δctb3 null mutant was fully restored when transformed with a functional CTB3 clone or when paired with a Δctb1-null mutant (defective in polyketide synthase) by cross feeding of the biosynthetic intermediates. Pathogenicity assays using detached tobacco leaves revealed that the Δctb3 disruptants drastically reduced lesion formation.
-
deletion of a mfs transporter like gene in Cercospora nicotianae reduces cercosporin toxin accumulation and fungal virulence
FEBS Letters, 2007Co-Authors: Mathias Choquer, Kuangren ChungAbstract: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 transporters belonging to the major facilitator superfamily (MFS). Disruption of the CTB4 gene resulted in a mutant that displayed a drastic reduction of cercosporin production and accumulation of an unknown brown pigment. Cercosporin was detected largely from fungal hyphae of ctb4 disruptants, but not from the surrounding medium, suggesting that the mutants were defective in both cercosporin biosynthesis and secretion. Cercosporin purified from the ctb4 disruptants exhibited toxicity to tobacco suspension cells, insignificantly different from wild-type, whereas the disruptants formed fewer lesions on tobacco leaves. The ctb4 null mutants retained normal resistance to cercosporin and other singlet oxygen-generating photosensitizers, indistinguishable from the parental strain. Transformation of a functional CTB4 clone into a ctb4 null mutant fully revived cercosporin production. Thus, we propose that the CTB4 gene encodes a putative MFS transporter responsible for secretion and accumulation of cercosporin.
-
Functional characterization of three genes encoding putative oxidoreductases required for cercosporin toxin biosynthesis in the fungus Cercospora nicotianae.
Microbiology (Reading England), 2007Co-Authors: Huiqin Chen, Miin-huey Lee, Kuangren ChungAbstract: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 biosynthetic pathway of C. nicotianae were functionally analysed. Replacement of each gene via double recombination was utilized to create null mutant strains that were completely impaired in cercosporin production as a consequence of specific interruption at the CTB5, CTB6 or CTB7 locus. Expression of CTB1, CTB5, CTB6, CTB7 and CTB8 was drastically reduced or nearly abolished when CTB5, CTB6 or CTB7 was disrupted. Production of cercosporin was revived when a functional gene cassette was introduced into the respective mutants. All ctb5, ctb6 and ctb7 null mutants retained wild-type levels of resistance against toxicity of cercosporin or singlet-oxygen-generating compounds, indicating that none of the genes plays a role in self-protection.
Marilyn Ehrenshaft - One of the best experts on this subject based on the ideXlab platform.
-
vitamin b6 pyridoxine and its derivatives are efficient singlet oxygen quenchers and potential fungal antioxidants
Photochemistry and Photobiology, 2007Co-Authors: Piotr Bilski, Margaret E. Daub, Marilyn Ehrenshaft, Colin F ChignellAbstract: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 (
-
Functional complementation between the PDX1 vitamin B6 biosynthetic gene of Cercospora nicotianae and pdxJ of Escherichia coli.
FEBS Letters, 2004Co-Authors: Denise K Wetzel, Marilyn Ehrenshaft, Sheri A Denslow, Margaret E. DaubAbstract: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 genes and PDX1 of Cercospora nicotianae. Although expression of pdxJ and pdxA in C. nicotianae pdx1 mutants, either separately or together, failed to complement the pyridoxine mutation in this fungus, expression of PDX1 restored pyridoxine prototrophy to the E. coli pdxJ mutant. Expression of PDX1 in the E. coli pdxA mutant restored very limited ability to grow on medium lacking pyridoxine. We conclude that the PDX1 gene of the alternative B(6) pathway encodes a protein responsible for synthesis of the pyridoxine ring.
-
A highly conserved gene for vitamin B6 biosynthesis may have consequences for stress and hormone responses in plants
Physiologia Plantarum, 2004Co-Authors: Cindy M. Graham, Marilyn Ehrenshaft, Georg Hausner, David M. ReidAbstract: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 Sci USA 96: 9374-9378, 1999). Expression of pvPDX1 in PDX1 mutants of C. nicotianae partially complements pyridoxine auxotrophy suggesting that a similar biosynthetic pathway for pyridoxine exists in both plants and fungi. In P. vulgaris, expression of pvPDX1 was induced by mechanical wounding via a mechanism that is independent of the production of AOS (active oxygen species). Furthermore, whereas the expression of pvPDX1 in P. vulgaris was up-regulated by treatment with 1-aminocyclopropane-1- carboxylic acid (ACC) treatment in a time course similar to that observed with wounding, expression was not consistently regulated by other treatments that caused a similar increase in ethylene production suggesting a more complicated regulatory pathway.
-
Cercosporin-deficient mutants by plasmid tagging in the asexual fungus Cercospora nicotianae
Molecular Genetics and Genomics, 2003Co-Authors: K.-r. Chung, Marilyn Ehrenshaft, D. K. Wetzel, Margaret E. DaubAbstract: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 integrated in multiple copies, and no increase in single-copy insertion was observed when enzymes were added to the transformation mixture. Out of 1873 transformants tested, 39 putative cercosporin toxin biosynthesis ( ctb ) mutants were recovered that showed altered levels of cercosporin production. Seven ctb mutants were recovered using pre-linearized plasmids without the addition of enzymes, and these were considered to be non-REMI mutants. The correlation between a specific insertion and a mutant phenotype was confirmed using rescued plasmids as gene disruption vectors in the wild-type strain. Six out of fifteen rescued plasmids tested yielded cercosporin-deficient transformants when re-introduced into the wild-type strain, suggesting a link between the insertion site and the cercosporin-deficient phenotype. Sequence analysis of a fragment flanking the insert site recovered from one insertion mutant showed it to be disrupted in sequences with high homology to the acyl transferase domain of polyketide synthases from other fungi. Disruption of this polyketide synthase gene ( CTB1 ) using a rescued plasmid resulted in mutants that were defective in cercosporin production. Thus, we provide the first molecular evidence that cercosporin is synthesized via a polyketide pathway as previously hypothesized.
-
Expression of the cercosporin toxin resistance gene (CRG1) as a dicistronic mRNA in the filamentous fungus Cercospora nicotianae
Current Genetics, 2003Co-Authors: Kuangren Chung, Margaret E. Daub, Marilyn EhrenshaftAbstract: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 either a CRG1 or a PUT1 gene probe. The 2.6-kb transcript identified only by the CRG1 probe was expressed constitutively, whereas the 2.0-kb transcript identified only by the PUT1 probe was differentially expressed in various media. Four cDNA clones containing CRG1 , PUT1 , and the CRG1 – PUT1 intergenic region were identified as part of the products from the 4.5-kb transcript. Both the 4.5-kb and 2.6-kb transcripts were not detectable in three crg1 -disrupted mutants, using the CRG1 probe. The 2.0-kb transcript, but not the 4.5-kb one was detected using the PUT1 probe in the three crg1 -disrupted mutants. Taken together, we conclude that the 4.5-kb transcript is a dicistronic mRNA of both CRG1 and PUT1 in the fungus C. nicotianae . This is the first example of a dicistronic mRNA identified in filamentous fungi.
Colin F Chignell - One of the best experts on this subject based on the ideXlab platform.
-
vitamin b6 pyridoxine and its derivatives are efficient singlet oxygen quenchers and potential fungal antioxidants
Photochemistry and Photobiology, 2007Co-Authors: Piotr Bilski, Margaret E. Daub, Marilyn Ehrenshaft, Colin F ChignellAbstract: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 (
-
symposium in print vitamin b6 pyridoxine and its derivatives are efficient singlet oxygen quenchers and potential fungal antioxidants
Photochemistry and Photobiology, 2000Co-Authors: Piotr Bilski, Margaret E. Daub, Marilyn Ehrenshaft, Colin F ChignellAbstract:Abstract 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 (physical and chemical quenching) kq values are: 5.5 × 107 M−1 s−1 for 1; 7.5 × 107 M−1 s−1 for 2, 6.2 ×107 M−1 s−1 for 3 and 7.5 × 107 M−1 s−1 for 4, all measured at pD 6.2. The quenching efficacy increased up to five times in alkaline solutions and decreased ∼10 times in ethanol. Significant contribution to total quenching by chemical reaction(s) is suggested by the degradation of all the vitamin derivatives by 1O2, which was observed as declining absorption of the pyridoxine moiety upon aerobic irradiat...
-
A Divergence in the Biosynthetic Pathway and a New Role for Vitamin B6
Biochemistry and Molecular Biology of Vitamin B6 and PQQ-dependent Proteins, 2000Co-Authors: Marilyn Ehrenshaft, Piotr Bilski, Colin F Chignell, Margaret E. Daub, Anne E. Jenns, Kuangren ChungAbstract:Studies on resistance of the fungus Cercospora nicotianae to singlet oxygen generating photosensitizers revealed new insights into the biological role of vitamin B6. Heterologous expression of a gene originally isolated because it complemented photosensitizer-sensitive mutants revealed that this gene (PDXI) is an essential component in vitamin B6 synthesis. Data base analysis has revealed that organisms contain either PDXI homologues or homologues to Escherichia coli biosynthetic genes but not homologues to both, suggesting the existence of divergent pathways. Furthermore, vitamin B6 is an efficient quencher of singlet oxygen and quenching occurs through a chemical interaction during which vitamin B6 is consumed.
-
a highly conserved sequence is a novel gene involved in de novo vitamin b6 biosynthesis
Proceedings of the National Academy of Sciences of the United States of America, 1999Co-Authors: Marilyn Ehrenshaft, Ming Y Li, Piotr Bilski, Colin F Chignell, Margaret E. DaubAbstract: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, although it shows no homology to previously identified pyridoxine synthesis genes identified in Escherichia coli. Sequence database analysis demonstrated that organisms encode either SOR1 or E. coli pyridoxine biosynthesis genes, but not both, suggesting that there are two divergent pathways for de novo pyridoxine biosynthesis in nature. Pathway divergence appears to have occurred during the evolution of the eubacteria. We also present data showing that pyridoxine quenches singlet oxygen at a rate comparable to that of vitamins C and E, two of the most highly efficient biological antioxidants, suggesting a previously unknown role for pyridoxine in active oxygen resistance.
Piotr Bilski - One of the best experts on this subject based on the ideXlab platform.
-
vitamin b6 pyridoxine and its derivatives are efficient singlet oxygen quenchers and potential fungal antioxidants
Photochemistry and Photobiology, 2007Co-Authors: Piotr Bilski, Margaret E. Daub, Marilyn Ehrenshaft, Colin F ChignellAbstract: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 (
-
symposium in print vitamin b6 pyridoxine and its derivatives are efficient singlet oxygen quenchers and potential fungal antioxidants
Photochemistry and Photobiology, 2000Co-Authors: Piotr Bilski, Margaret E. Daub, Marilyn Ehrenshaft, Colin F ChignellAbstract:Abstract 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 (physical and chemical quenching) kq values are: 5.5 × 107 M−1 s−1 for 1; 7.5 × 107 M−1 s−1 for 2, 6.2 ×107 M−1 s−1 for 3 and 7.5 × 107 M−1 s−1 for 4, all measured at pD 6.2. The quenching efficacy increased up to five times in alkaline solutions and decreased ∼10 times in ethanol. Significant contribution to total quenching by chemical reaction(s) is suggested by the degradation of all the vitamin derivatives by 1O2, which was observed as declining absorption of the pyridoxine moiety upon aerobic irradiat...
-
A Divergence in the Biosynthetic Pathway and a New Role for Vitamin B6
Biochemistry and Molecular Biology of Vitamin B6 and PQQ-dependent Proteins, 2000Co-Authors: Marilyn Ehrenshaft, Piotr Bilski, Colin F Chignell, Margaret E. Daub, Anne E. Jenns, Kuangren ChungAbstract:Studies on resistance of the fungus Cercospora nicotianae to singlet oxygen generating photosensitizers revealed new insights into the biological role of vitamin B6. Heterologous expression of a gene originally isolated because it complemented photosensitizer-sensitive mutants revealed that this gene (PDXI) is an essential component in vitamin B6 synthesis. Data base analysis has revealed that organisms contain either PDXI homologues or homologues to Escherichia coli biosynthetic genes but not homologues to both, suggesting the existence of divergent pathways. Furthermore, vitamin B6 is an efficient quencher of singlet oxygen and quenching occurs through a chemical interaction during which vitamin B6 is consumed.
-
a highly conserved sequence is a novel gene involved in de novo vitamin b6 biosynthesis
Proceedings of the National Academy of Sciences of the United States of America, 1999Co-Authors: Marilyn Ehrenshaft, Ming Y Li, Piotr Bilski, Colin F Chignell, Margaret E. DaubAbstract: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, although it shows no homology to previously identified pyridoxine synthesis genes identified in Escherichia coli. Sequence database analysis demonstrated that organisms encode either SOR1 or E. coli pyridoxine biosynthesis genes, but not both, suggesting that there are two divergent pathways for de novo pyridoxine biosynthesis in nature. Pathway divergence appears to have occurred during the evolution of the eubacteria. We also present data showing that pyridoxine quenches singlet oxygen at a rate comparable to that of vitamins C and E, two of the most highly efficient biological antioxidants, suggesting a previously unknown role for pyridoxine in active oxygen resistance.