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The glutathione‐deficient, cadmium‐sensitive mutant, cad2–1 , of Arabidopsis thaliana is deficient in γ‐glutamylcysteine synthetase
Author(s) -
Cobbett Christopher S.,
May Mike J.,
Howden Ross,
Rolls Barbara
Publication year - 1998
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1046/j.1365-313x.1998.00262.x
Subject(s) - biology , mutant , biochemistry , cysteine , microbiology and biotechnology , glutathione , gene , enzyme , complementary dna
Summary This paper reports that the glutathione (GSH)‐deficient mutant,cad2–1, of Arabidopsis is deficient in the first enzyme in the pathway of GSH biosynthesis, γ‐glutamylcysteine synthetase (GCS). The mutant accumulates a substrate of GCS, cysteine, and is deficient in the product, γ‐glutamylcysteine.In vitroenzyme assays showed that thecad2–1mutant has 40% of wild‐type levels of GCS activity but is unchanged in the activity of the second enzyme in the pathway, GSH synthetase. TheCAD2locus maps to chromosome 4 and is tightly linked to a gene,GSHA, identified by a previously isolated cDNA. A genomic clone ofGSHAcomplements both the phenotypic and biochemical deficiencies of thecad2–1mutant. The nucleotide sequence of the gene has been determined and, in the mutant, this gene contains a 6 bp deletion within an exon. These data demonstrate that theCAD2gene encodes GCS. Thecad2–1mutation is close to the conserved cysteine which is believed to bind the substrate glutamate and the specific inhibitor L‐buthionine‐[S,R] sulfoximine (BSO). Both root growth and GCS activity of thecad2–1mutant was less sensitive than the wild‐type to inhibition by BSO, indicating that the mutation may alter the affinity of the inhibitor binding site.