INCREASED RESISTANCE OF ARABIDOPSIS CPR5 MUTANT TO H2O2- INDUCED PHOTOOXIDATION

Abstract

cpr5 is predicted to be a putative transmembrane protein involved in several cellular processes, including signal transduction plant defense and trichome development. The mutation of the cpr5 gene increases the resistance of Arabidopsis to pathogens. In this study, we show an In vitro increased resistance of cpr5 leaves to hydrogen peroxide-induced photooxidation. Both fluorescence parameters (including Fv/Fm, фPSⅡ, qP and NPQ) and the activities of two anti-oxidative enzymes (SOD and APX) were used to evaluate the response of mutant and wild-type leaves to H2O2 treatment. During a 360-min., treatment, both mutant and wild-type leaves showed a time course dependent decrease trend in Fv/Fm values. However, the decrease rate for mutant leaves (0.046/min) was nearly twenty five-fold lower than that for wild-type leaves (0.101/min). The leaves of cpr5 dramatically delayed the reduction of фPSⅡ values and showed a different profile of фPSⅡ from the wild-type. At 240 min., of treatment, the value of фPSⅡ for the mutant leaves was nearly six-fold as that of the wild-type. The rates of cellular membrane leakage were constitutively lower in the cpr5 leaves than in the wild-type. In addition, the cpr5 leaves showed slightly higher activities of the SOD and APX enzymes than did the wild type. These results indicated that cpr5 mutant increased both anti-oxidative capability and the stability of PSII to H2O2-induced photooxidation.