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

Author:
Liao, Dengqun, Pajak, Agnieszka, Karcz, Steven R., Chapman, B. Patrick, Sharpe, Andrew G., Austin, Ryan S., Datla, Raju, Dhaubhadel, Sangeeta, Marsolais, Frédéric
Source:
Journal of experimental botany 2012 v.63 no.17 pp. 6283-6295
ISSN:
0022-0957
Subject:
Kunitz-type proteinase inhibitor, Phaseolus vulgaris, acetyltransferases, amino acid composition, beans, biosynthesis, cystathionine, cysteine, gene expression regulation, genes, homocysteine, lectins, legumin, methionine, methionine S-methyltransferase, microarray technology, nonprotein amino acids, phaseolin, phytohemagglutinin, proteomics, seed development, seeds, serine, sulfur, transporters
Abstract:
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.
Agid:
1188668