Repair of UV-B-induced damage of Photosystem II and DNA in Chlamydomonas reinhardtii

摘要

Depletion of the stratospheric ozone layer is believed to lead to an increase in the level of UV-B (290-320 nm) reaching to the Earth's surface. UV-B radiation causes the harmful effects on the various functions and components in plants, such as theactivities of photosystem II (PS II), Rubisco and ATPase, the degradation of PS II reaction center proteins (D1 and D2), and the lesions of DNA (Strid et al., 1994; Britt, 1996; Vass, 1997; Jansen et al., 1998). There is a consensus that UV-B radiationcauses the severe damage of PS II electron transport activity, but no or a little effect on PS I (Strid et al., 1994; Vass, 1997). The action sites in the PS II components of UV-B radiation have been suggested to be the acceptor sites (Q_A, Q_B and plastoquinone pool), theredox-active tyrosine residues (Tyr-Z and Tyr-D) and the water-oxidizing complex. UV-B irradiation of living organisms causes the structural modification of DNAincluding formation of photoproducts. The most common DNA photoproducts are cyclobutane pyrimidine dimers (CPD) and the pyrimidine (6-4) pyrimidinone photoproducts (6-4 PP) (Britt, 1996; Jansen et al., 1998). Photoproducts formed byUV-B radiation cause to eliminate expression of a transcriptional unit.