ABSENCE OF NICOTIANAMINE SYNTHASE ACTIVITY IN THE TOMATO MUTANT CHLORONERVA

Nicotianamine is proposed to play a key role in iron (Fe) metabolism i n plants. In graminaceous plants nicotianamine is the precursor for ph ytosiderophores, and the activity of the nicotianamine synthase is str ongly enhanced under Fe deficiency. The tomato mutant 'chloronerva' (L ycopersicon esculentum Mill. cv. chloronerva) lacks nicotianamine and has a disturbed Fe homeostasis. Our objective was to compare nicotiana mine synthase activity of the mutant 'chloronerva' with the wild form ('Bonner Beste'). In contrast to the wild form which as high nicotiana mine synthase activity, no activity of the enzyme could be detected in roots or shoots of 'chloronerva', regardless of the iron nutritional status of the plants. This finding might allow comparison of promoter regions of the genes of 'chloronerva', 'Bonner Beste', and graminaceou s species to clarify the regulatory mechanism of gene expression by th e Fe nutritional status in graminaceous species.