AUTHOR=Liao Dengqun , Cram Dustin , Sharpe Andrew G., Marsolais Frédéric 

TITLE=Transcriptome Profiling Identifies Candidate Genes Associated with the Accumulation of Distinct Sulfur γ-Glutamyl Dipeptides in Phaseolus vulgaris and Vigna mungo Seeds

JOURNAL=Frontiers in Plant Science

VOLUME=4

YEAR=2013

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2013.00060

DOI=10.3389/fpls.2013.00060

ISSN=1664-462X

ABSTRACT=<p>Common bean (<italic>Phaseolus vulgaris</italic>) and black gram (<italic>Vigna mungo</italic>) accumulate γ-Glutamyl-<italic>S</italic>-methylcysteine and γ-Glutamyl-methionine in seed, respectively. Transcripts were profiled by 454 pyrosequencing data at a similar developmental stage coinciding with the beginning of the accumulation of these metabolites. Expressed sequence tags were assembled into Unigenes, which were assigned to specific genes in the early release chromosomal assembly of the <italic>P. vulgaris</italic> genome. Genes involved in multiple sulfur metabolic processes were expressed in both species. Expression of <italic>Sultr3</italic> members was predominant in <italic>P. vulgaris</italic>, whereas expression of <italic>Sultr5</italic> members predominated in <italic>V. mungo</italic>. Expression of the cytosolic SERAT1;1 and -1;2 was approximately fourfold higher in <italic>P. vulgaris</italic> while expression of the plastidic SERAT2;1 was twofold higher in <italic>V. mungo</italic>. Among <italic>BSAS</italic> family members, <italic>BSAS4;1</italic>, encoding a cytosolic cysteine desulfhydrase, and <italic>BSAS1;1</italic>, encoding a cytosolic <italic>O</italic>-acetylserine sulphydrylase were most highly expressed in both species. This was followed by <italic>BSAS3;1</italic> encoding a plastidic β-cyanoalanine synthase which was more highly expressed by 10-fold in <italic>P. vulgaris</italic>. The data identify BSAS3;1 as a candidate enzyme for the biosynthesis of <italic>S</italic>-methylcysteine through the use of methanethiol as substrate instead of cyanide. Expression of <italic>GLC1</italic> would provide a complete sequence leading to the biosynthesis of γ-Glutamyl-<italic>S</italic>-methylcysteine in plastids. The detection of <italic>S</italic>-methylhomoglutathione in <italic>P. vulgaris</italic> suggested that homoglutathione synthetase may accept, to some extent, γ-Glutamyl-<italic>S</italic>-methylcysteine as substrate, which might lead to the formation of <italic>S</italic>-methylated phytochelatins. In conclusion, 454 sequencing was effective at revealing differences in the expression of sulfur metabolic genes, providing information on candidate genes for the biosynthesis of distinct sulfur amino acid γ-Glutamyl dipeptides between <italic>P. vulgaris</italic> and <italic>V. mungo</italic>.</p>