A Medicago truncatula Homoglutathione Synthetase Is Derived from Glutathione Synthetase by Gene Duplication
Open Access
- 1 August 2001
- journal article
- Published by Oxford University Press (OUP) in Plant Physiology
- Vol. 126 (4) , 1706-1715
- https://doi.org/10.1104/pp.126.4.1706
Abstract
Glutathione (GSH) and homo-GSH (hGSH) are the major low-molecular weight thiols synthesized in Medicago truncatula. TwoM. truncatula cDNAs (gshs1 andgshs2) corresponding to a putative GSH synthetase (GSHS) and a putative hGSH synthetase (hGSHS) were characterized. Heterologous expression of gshs1 and gshs2 cDNAs in anEscherichia 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 β-alanine and glycine by hGSHS. Phylogenetic analysis of GSHS2 and GSHS1 with other eukaryotic GSHS sequences indicated that gshs2 and gshs1are 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 ofgshs1 and gshs2 occurred via a tandem duplication.Keywords
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