REGULATION AND ROLE OF THE ALTERNATIVE OXIDASE IN CHILLING INJURY OF GREEN BELL PEPPER (Capsicum annuum L.)

Mature green bell peppers (Capsicum annuum L.) were stored at 15°C, 4°C and 1°C for 6 to 8 days. Peppers exhibited fewer chilling injury (CI) symptoms (sheet pitting, seed darkening, increased respiration rates and decreased chlorophyll fluorescence ratios) after storage at 4°C than at 1°C. Mitochondria isolated from peppers stored at 1°C produced more superoxide than those from peppers stored at 4°C, but less than those from fresh peppers and peppers stored at 15°C. Western blot analysis of the mitochondrial proteins showed a substantial increase in alternative oxidase (AOX) protein in mitochondria isolated from peppers stored at 4°C compared to those stored at either 1°C or 15°C. Results support a role for the AOX, along with antioxidants and the reactive oxygen species (ROS) scavenging enzymes in the mechanism by which plant tissues are protected from chilling-induced oxidative stress.