Characterization of the salt-inducible methionine synthase from barley leaves

Abstract

We have cloned a cDNA encoding a putative methionine synthase from barley leaves by differential display. The full-length cDNA contained an open reading frame (2295 bp) encoding a deduced 765 amino acid polypeptide without any typical signal sequence, suggesting that it is localized in the cytosol. Expression of this gene was induced by salt stress in barley leaves. The gene expression was induced by light, but more strongly induced under salt, drought and cold stresses and by treatment with ABA or H 2O 2. A complementation test using a yeast mutant lacking the ability to synthesize methionine showed that this gene complements the yeast mutant under both non-stress and high-salinity (1 M NaCl) conditions. Although plant methionine synthase is known to be induced at the level of mRNA but not at that of protein, we found that the protein level of methionine synthase is also significantly increased in barley leaves under salt stress.