Thermostability and Photostability of Photosystem II in Leaves of the Chlorina-f2 XXXX Mutant Deficient in Light-Harvesting Chlorophyll a/b Protein Complexes.

@entity11079 @entity2247 @entity26 @entity425 @entity8291 @entity942
The chlorophyll-b-less chlorina-f2 @entity2247 mutant is deficient in the major as well as some minor light-harvesting chlorophyll-protein complexes of photosystem II (LHCII). Although the @entity942 had relatively minor repercussions on the leaf photosynthetic performances, the responses of photosystem II (PSII) to elevated temperatures and to bright light were markedly modified. The chlorina-f2 mutation noticeably reduced the thermostability of PSII, with thermal denaturation of PSII starting at about 35[deg]C and 38.5[deg]C in chlorina-f2 and in the wild type, respectively. The increased susceptibility of PSII to @entity8291 in chlorina-f2 leaves was due to the weakness of its electron donor side, with moderate @entity8291 causing detachment of the 33-kD extrinsic PSII protein from the @entity26 -evolving complex. Prolonged dark adaptation of chlorina-f2 leaves was also observed to inhibit the PSII donor side. However, @entity425 slowly reversed the dark-induced inhibition of PSII in chlorina-f2 and cancelled the difference in PSII thermostability observed between chlorina-f2 and wild-type leaves. The mutant was more sensitive to photoinhibition than the wild type, with strong light stress impairing the PSII donor side in chlorina-f2 but not in the wild type. This difference was not observed in anaerobiosis or in the presence of @entity11079 , @entity11079 . The acceptor side of PSII was only slightly affected by the mutation and/or the aforementioned stress conditions. Taken together, our results indicate that LHCII stabilize the PSII complexes and maintain the water-oxidizing system in a functional state under varying environmental conditions.
