INDUCTION OF PLASMA-MEMBRANE NADH-FERRICYANIDE REDUCTASE FOLLOWING IRON STRESS IN TOMATO ROOTS

Roots from tomato (Lycopersicon esculentum) plants grown in the absence of iron developed higher plasma membrane-bound NADH-ferricyanide and NADH-Fe3+ citrate reductase activities. Plasma membrane vesicles obtained by aqueous two-phase partitioning were solubilized with 1% (w/w) lysophosphatidylcholine and membrane proteins separated by gel filtration using Fast Protein Liquid Chromatography (FPLC). An NADH-ferricyanide reductase component with an apparent molecular mass of about 70 kDa was strongly increased in roots from iron starved plants with respect to controls, while two other peaks of NADH-ferricyanide reductase activity were not affected. This response was not observed in the T3820fer (JvL) tomato mutant, as the 70 kDa protein was absent both in the control and the Fe-stressed roots. Other redox enzymes, namely NADH- and NAD(P)H-duroquinone reductases, were scarcely affected by the iron status of the tomato plants.