重写cpr5-3重写cpr5-3.doc

Resistance of Arabidopsis cpr5 mutants to photooxidation induced by H2O2 HUANG Hong-Ying1，2, PENG Chang-Lian1* 1) Key Laboratory of Ecology and Environmental Science in Guangdong Higher Education, College of Life Sciences, South China Normal University, Guangzhou 510631,China; 2) Department of Chemistry and Life science, Xiangnan College,Chenzhou,Hunan, 423000,China Abstract: Chlorophyll fluorescence imaging and antioxidative capability in detached leaf discs of Arabidopsis cpr5 mutant and its wild type (Col) were investigated under photooxidation induced by exogenous H2O2. In comparison with wild type (WT) plant, photooxidation resulted in smaller decreases in fluorescence parameters (Fv/Fm，фPSⅡ，qP and NPQ) and the activities of SOD and APX, and an increase in cell membrane leakage rate in leaves of cpr5 mutant. After treatment for 240 min, фPSⅡ in leaves of cpr5 mutant remained 0.13, but nearly zero in WT. The sequence of sensitivity to photooxidation in leaves of two phenotypes were cpr5WT. The results indicated that cpr5 mutant exhibited higher antioxidative capability and more stable PSII than that in WT under photooxidative stress induced by exogenous H2O2. Key words: Arabidopsis; cpr5 mutant; photooxidation; chlorophyll fluorescence imaging; antioxidative capacity. CPR5 gene is involved in several processes including signal transduction, cell proliferation , cell death and pathogendefence responses. CPR5 gene plays a repressive role in early processes for the induction of general pathogendefence responses (Yoshida et al., 2002). CPR5 gene encodes a novel putative transmembrane protein containing five (pathogenesis-related genes) putative transmembrane helices at the C terminus. CPR5 is predicted to be a Type IIIa membrane protein, with the N-terminus being cytoplasmatic (PSORT). In addition, a nuclear localization signal (NLS) is found at the N-terminus at position 40-56 (PSORT) (Kirik et al., 2001). Mutations in cpr5 have pleiotropic effects on t