Transcripts of sulphur metabolic genes are co-ordinately regulated in developing seeds of common bean lacking phaseolin and major lectins.
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.
Agriculture and Agri-Food Canada, Genomics and Biotechnology, Southern Crop Protection and Food Research Centre, 1391 Sandford St., London, Ontario N5V 4T3,  Canada.
Dengqun
D
Liao
Agnieszka
A
Pajak
Steven R
SR
Karcz
B Patrick
BP
Chapman
Andrew G
AG
Sharpe
Ryan S
RS
Austin
Raju
R
Datla
Sangeeta
S
Dhaubhadel
Frédéric
F
Marsolais
D000596:Amino Acids / Q000378:metabolism; D016000:Cluster Analysis; D003545:Cysteine / Q000031:analogs & derivatives / Q000378:metabolism*; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D037102:Lectins / Q000378:metabolism*; D008715:Methionine / Q000378:metabolism*; D020411:Oligonucleotide Array Sequence Analysis; D027805:Phaseolus / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D018749:RNA, Plant / Q000235:genetics; D055314:Seed Storage Proteins / Q000235:genetics / Q000378:metabolism; D012639:Seeds / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D012694:Serine / Q000031:analogs & derivatives / Q000378:metabolism; D013455:Sulfur / Q000378:metabolism*
D000596:Amino Acids; D037102:Lectins; D010940:Plant Proteins; D012333:RNA, Messenger; D018749:RNA, Plant; D055314:Seed Storage Proteins; C048826:phaseolin protein, Phaseolus vulgaris; D012694:Serine; D013455:Sulfur; C008425:S-methylcysteine; D008715:Methionine; C043943:O-acetylserine; D003545:Cysteine