Effects of ultraviolet-B light on photosystem II phosphoproteins in barleywild type and its chlorophyll b-less mutant chlorina f2

The effects of ultraviolet-B light on the level and steady-state phosphoryl ation of photosystem II proteins have been studied in barley wild type and its chlorophyll b-less mutant chlorina f2. In the wild type, ultraviolet-B radiation is found to promote dephosphorylation of all thylakoid phosphopro teins. In addition, for reaction-centre proteins D1 and D2, dephosphorylati on is paralleled by degradation. Photosystem II core proteins in the mutant are not found to be significantly phosphorylated in any experimental condi tions, and loss of D1 and D2 reaction-centre proteins is slightly faster th an in the wild type. These results are consistent with the possibility that phosphorylation of reaction-centre proteins affects their stability, possi bly by slowing down the rate of degradation, as in the case of visible ligh t [E. Rintamaki, R. Kettunen, E.-M. Aro, J. Biol. Chem. 271 (1996) 14870-14 875]. (C) 1999 Elsevier Science S.A. All rights reserved.