CHARACTERIZATION OF A GLUTATHIONE-REDUCTASE GENE AND ITS GENETIC-LOCUS FROM PEA (PISUM-SATIVUM L)

A cDNA encoding the chloroplast/mitochondrial form of glutathione redu ctase (GR; EC 1.6.4.2) from pea (Pisum sativum L.) was used to map a s ingle CR locus, named GOR1. In two domesticated genotypes of pea (cv. Birte and JI 399) it is likely that the GOR1 locus contains a single g ene. However, in a semi-domesticated land race of pea (JI 281) two dis tinct but closely related sets of GR gene sequences were detected at t he GOR1 locus. The extra GR sequences in JI 281 represent either a sec ond intact gene or a partial or pseudogene copy. A GR gene was cloned from cv. Birte, sequenced and its structure analysed. No feature of th e transcription or structure of the gene suggested a mechanism for gen erating any more than one form of GR. From these data plus previously published biochemical evidence we suggest that a second, distinct gene encoding for the cytosolic form of GR should be present in peas. The GOR1-encoded GR mRNA can be detected in all main organs of the plant a nd no alternative spliced species was present which could perhaps acco unt for the generation of multiple isoforms of GR. The mismatch betwee n the number of charge-separable isoforms in pea and the proposed numb er of genes suggests that different GR isoforms arise by some form of post-translational modification.