Expression of defense genes and activities of antioxidant enzymes in rice resistance to rice stripe virus and small brown planthopper.

The rice variety Tai06-1 is resistant to rice stripe disease and Xiushui63 is a highly susceptible rice variety to this disease. These two varieties were used to analyze the expression patterns of defense genes and antioxidant defense responses at the seedling stage, upon feeding with viruliferous small brown planthopper (SBPH) and nonviruliferous SBPH, respectively. The expression levels of CP (coat protein) gene of rice stripe virus (RSV) were higher upon feeding with viruliferous SBPH in Xiushui63 than in Tai06-1 throughout most of the experimental period, suggesting that RSV replicaiton is disturbed in Tai06-1 but not in Xiushui63, therefore, the resistance to RSV is higher in Tai06-1 than in Xiuhsui63. We found that defense genes PR1a (pathogenesis-related class 1a), PAL (phenylalanine ammonia-lyase), and CHS (chalcone synthase) may play roles in the defense responses to both RSV and SBPH in Tai06-1, and PR4 and PR10a may only participate in defending against SBPH attack but not against RSV infection in Tai06-1. Our data reveal that Gns1 (1,3; 1,4-β-glucanase) may participate in the defense responses to both RSV and SBPH in Xiushui63 but not in Tai06-1, and LOX (lipoxygenase) may only participate in defending against to SBPH in both Tai06-1 and Xiushui63. The antioxidant enzymes superoxide dismutase, peroxidase, catalase, hydrogen peroxide, and malondialdehyde coordinately participate in the resistance to RSV in Tai06-1, and that oxidative damage is less in Tai06-1 than in Xiushui63.