Effect of iron deficiency on S‐adenosylmethionine synthetase in barley roots

Abstract

S‐adenosyl‐L‐methionine (SAM) synthetase, which catalyzes methionine to SAM, is one of the enzymes involved in the biosynthesis of the mugineic acid‐family phytosiderophores (MAs). The MAs are secreted from grass roots under iron (Fe)‐deficient conditions. We compared the SAM synthetase activities between Fe‐deficient and Fe‐sufficient barley roots. However, no difference was observed. Then we performed Northern hybridization analysis between Fe‐deficient and Fe‐sufficient barley tissues by a cDNA fragment of SAM synthetase isolated from barley. No increase in the amount of mRNA was detected in the Fe‐deficient barley roots as compared to the Fe‐sufficient ones. It was suggested that the first step in the phytosiderophore biosynthesis induced under the Fe‐deficiency is not SAM synthetase, but NA synthase and the second induced step is NA aminotransferase.