Cadmium inhibits epoxidation of diatoxanthin to diadinoxanthin in the xanthophyll cycle of the marine diatom Phaeodactylum tricornutum

Cd has pleiotropic effects on plant physiology and in particular on photosy nthesis. It has not been established yet if Cd alters the functioning of th e xanthophyll cycle. To answer this question, an exponentially growing cult ure of the marine diatom Phaeodactylum tricornutum was incubated with Cd (2 0 mg/l) for 24 h and irradiated with a light activating the xanthophyll cyc le, which in diatoms, consists of the reversible deepoxidation of diadinoxa nthin to diatoxanthin. The measurements show that the deepoxidation step is not influenced by Cd. In contrast, the Cd concentration used sharply inhib its the epoxidation of diatoxanthin to diadinoxanthin. (C) 2001 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All r ights reserved.