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-ß-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.

[Apoptosis of HL-60 cells induced by crystal proteins from Bacillus thuringiensis Bt9875].

OBJECTIVE: To study the effect of Bt9875 crystal protein treated with proteinase K on human cancer cells, HL-60. METHODS: We used the methods of Thiazolyl Blue Tetrazolium Bromide, fluorescence microscopy examination, agarose gel electrophores and flow cytometry to detect the growth inhibition rate and apoptosis characters of the HL-60 cells that were treated with different concentration of Bt9875 crystal protein. RESULTS: Bt9875 crystal protein inhibited the growth of HL-60 cells evidently in a dose-dependent manner, with minimal effects on normal human peripheral blood mononuclear cells (PBMCs). The nuclei of HL-60 cells showed the characteristics of apoptosis. The analysis by flow cytometry indicated that the apoptosis rate of HL-60 cells was 52% after treatment with Bt9875 crystal protein (100 microg/mL). DNA analyzed by agarose gel electrophoresis showed "ladder" pattern. CONCLUSION: Bt9875 crystal protein could inhibit the growth of HL-60 and induced its apoptosis, which provided a foundation for use of Bt9875 crystal protein to cure the acute myeloid leukemia.

[Population fluctuation of main pathogens and their antagonistic bacteria in cucumber rhizosphere].

The investigation on the population fluctuation of main pathogens Pythium spp. and Fusarium oxysporum f. cucumerinum in the rhizosphere of four cucumber varieties showed that there was a significant difference in population number of pathogens for different cucumber varieties and for different growth stages of the same variety, which was in accordance with the regular disease incidence pattern. The population number of Pythium spp. was significantly higher at cucumber creeping stage than at its other growth stages, while that of Fusarium oxysporum f. sp. cucumerinum was the highest at cucumber principal-fruiting stage. There was a closer positive relationship between two test pathogens and their antagonistic bacteria, with the correlation coefficient being 0.95 and 0.81, respectively.