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A Medicago truncatula homoglutathione synthetase is derived from glutathione synthetase by gene duplication

Author:
Frendo, P., Jimenez, M.J.H., Mathieu, C., Duret, L., Gallesi, D., Van de Sype, G., Herouart, D., Puppo, A.
Source:
Plant physiology 2001 v.126 no.4 pp. 1706-1715
ISSN:
0032-0889
Subject:
glutathione, leucine, complementary DNA, molecular weight, proline, alanine, phylogeny, amino acid sequences, gene expression, genes, nucleotide sequences, genetic complementation, glutathione synthase, glycine (amino acid), Medicago truncatula
Abstract:
Glutathione (GSH) and homo-GSH (hGSH) are the major low-molecular weight thiols synthesized in Medicago truncatula. Two M. truncatula cDNAs (gshs1 and gshs2) corresponding to a putative GSH synthetase (GSHS) and a putative hGSH synthetase (hGSHS) were characterized. Heterologous expression of gshs1 and gshs2 cDNAs in an Escherichia coli strain deficient in GSHS activity showed that GSHS1 and GSHS2 are a GSHS and an hGSHS, respectively. Leucine-534 and proline-535 present in hGSHS were substituted by alanines that are conserved in plant GSHS. These substitutions resulted in a strongly stimulated GSH accumulation in the transformed E. coli strain showing that these residues play a crucial role in the differential recognition of beta-alanine and glycine by hGSHS. Phylogenetic analysis of GSHS2 and GSHS1 with other eukaryotic GSHS sequences indicated that gshs2 and gshs1 are the result of a gene duplication that occurred after the divergence between Fabales, Solanales, and Brassicales. Analysis of the structure of gshs1 and gshs2 genes shows they are both present in a cluster and in the same orientation in the M. truncatula genome, suggesting that the duplication of gshs1 and gshs2 occurred via a tandem duplication.
Agid:
668533