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A highly conserved sequence is a novel gene involved in de novo vitamin B6 biosynthesis.

ABSTRACT: 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.

SUBMITTER: Ehrenshaft M

PROVIDER: S-EPMC17790 | biostudies-literature | 1999 Aug

REPOSITORIES: biostudies-literature

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A highly conserved sequence is a novel gene involved in de novo vitamin B6 biosynthesis.

Ehrenshaft M M Bilski P P Li M Y MY Chignell C F CF Daub M E ME

Proceedings of the National Academy of Sciences of the United States of America 19990801 16

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 ...[more]

PMID: 10430950

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Project description:BackgroundSaponins are mainly amphipathic glycosides that posses many biological activities and confer potential health benefits to humans. Inspite of its medicinal attributes most of the triterpenes and enzymes involved in the saponin biosynthesis remains uncharacterized at the molecular level. Since the major steroidal components are present in the roots of A. racemosus our study is focussed on the comparative denovo transcriptome analysis of root versus leaf tissue and identifying some root specific transcripts involved in saponin biosynthesis using high-throughput next generation transcriptome sequencing.ResultsAfter sequencing, de novo assembly and quantitative assessment, 126861 unigenes were finally generated with an average length of 1200 bp. Then functional annotation and GO enrichment analysis was performed by aligning all-unigenes with public protein databases including NR, SwissProt, and KEGG. Differentially expressed genes in root were initially identified using the RPKM method using digital subtraction between root and leaf. Twenty seven putative secondary metabolite related transcripts were experimentally validated for their expression in root or leaf tissue using q-RT PCR analysis. Most of the above selected transcripts showed preferential expression in root as compared to leaf supporting the digitally subtracted result obtained. The methyl jasmonate application induces the secondary metabolite related gene transcripts leading to their increased accumulation in plants. Therefore, the identified transcripts related to saponin biosynthesis were further analyzed for their induced expression after 3, 5 and 12 hours of exogenous application of Methyl Jasmonate in tissue specific manner.ConclusionsIn this study, we have identified a large set of cDNA unigenes from A. racemosus leaf and root tissue. This is the first transcriptome sequencing of this non-model species using Illumina, a next generation sequencing technology. The present study has also identified number of root specific transcripts showing homology with saponin biosynthetic pathway. An integrated pathway of identified saponin biosynthesis transcripts their tissue specific expression and induced accumulation after methyl jasmonate treatment was discussed.

Project description:Jute fiber, extracted from stem bast, is called golden fiber. It is essential for fiber improvement to discover the genes associated with jute development at the vegetative growth stage. However, only 858 EST sequences of jute were deposited in the GenBank database. Obviously, the public available data is far from sufficient to understand the molecular mechanism of the fiber biosynthesis. It is imperative to conduct transcriptomic sequence for jute, which can be used for the discovery of a number of new genes, especially genes involved in cellulose biosynthesis.A total of 79,754,600 clean reads (7.98 Gb) were generated using Illumina paired-end sequencing. De novo assembly yielded 48,914 unigenes with an average length of 903 bp. By sequence similarity searching for known proteins, 27,962 (57.16 %) unigenes were annotated for their function. Out of these annotated unigenes, 21,856 and 11,190 unigenes were assigned to gene ontology (GO) and euKaryotic Ortholog Groups (KOG), respectively. Searching against the Kyoto Encyclopedia of Genes and Genomes Pathway database (KEGG) indicated that 14,216 unigenes were mapped to 268 KEGG pathways. Moreover, 5 Susy, 3 UGPase, 9 CesA, 18 CSL, 2 Kor (Korrigan), and 12 Cobra unigenes involving in cellulose biosynthesis were identified. Among these unigenes, the unigenes of comp11264_c0 (SuSy), comp24568_c0 (UGPase), comp11363_c0 (CesA), comp11363_c1 (CesA), comp24217_c0 (CesA), and comp23531_c0 (CesA), displayed relatively high expression level in stem bast using FPKM and RT-qPCR, indicating that they may have potential value of dissecting mechanism on cellulose biosynthesis in jute. In addition, a total of 12,518 putative gene-associate SNPs were called from these assembled uingenes.We characterized the transcriptome of jute, discovered a broad survey of unigenes associated with vegetative growth and development, developed large-scale SNPs, and analyzed the expression patterns of genes involved in cellulose biosynthesis for bast fiber. All these provides a valuable genomics resource, which will accelerate the understanding of the mechanism of fiber development in jute.

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A highly conserved sequence is a novel gene involved in de novo vitamin B6 biosynthesis.

Publications

A highly conserved sequence is a novel gene involved in de novo vitamin B6 biosynthesis.

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