Journal Article

Transcripts of sulphur metabolic genes are co-ordinately regulated in developing seeds of common bean lacking phaseolin and major lectins

Dengqun Liao, Agnieszka Pajak, Steven R. Karcz, B. Patrick Chapman, Andrew G. Sharpe, Ryan S. Austin, Raju Datla, Sangeeta Dhaubhadel and Frédéric Marsolais

in Journal of Experimental Botany

Published on behalf of Society for Experimental Biology

Volume 63, issue 17, pages 6283-6295
Published in print October 2012 | ISSN: 0022-0957
Published online October 2012 | e-ISSN: 1460-2431 | DOI: https://dx.doi.org/10.1093/jxb/ers280

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The lack of phaseolin and phytohaemagglutinin in common bean (dry bean, Phaseolus vulgaris) is associated with an increase in total cysteine and methionine concentrations by 70% and 10%, respectively, mainly at the expense of an abundant non-protein amino acid, S-methyl-cysteine. Transcripts were profiled between two genetically related lines differing for this trait at four stages of seed development using a high density microarray designed for common bean. Transcripts of multiple sulphur-rich proteins were elevated, several previously identified by proteomics, including legumin, basic 7S globulin, albumin-2, defensin, albumin-1, the Bowman–Birk type proteinase inhibitor, the double-headed trypsin inhibitor, and the Kunitz trypsin inhibitor. A co-ordinated regulation of transcripts coding for sulphate transporters, sulphate assimilatory enzymes, serine acetyltransferases, cystathionine β-lyase, homocysteine S-methyltransferase and methionine gamma-lyase was associated with changes in cysteine and methionine concentrations. Differential gene expression of sulphur-rich proteins preceded that of sulphur metabolic enzymes, suggesting a regulation by demand from the protein sink. Up-regulation of SERAT1;1 and -1;2 expression revealed an activation of cytosolic O-acetylserine biosynthesis. Down-regulation of SERAT2;1 suggested that cysteine and S-methyl-cysteine biosynthesis may be spatially separated in different subcellular compartments. Analysis of free amino acid profiles indicated that enhanced cysteine biosynthesis was correlated with a depletion of O-acetylserine. These results contribute to our understanding of the regulation of sulphur metabolism in developing seed in response to a change in the composition of endogenous proteins.

Keywords: Common bean; cysteine; methionine; seed proteins; sulphur metabolism; transcript profiling

Journal Article.  9484 words.  Illustrated.

Subjects: Plant Sciences and Forestry

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