The Elementary Study On The Resistance Mechanism Mediated By XA21

Xa21, the first disease resistance gene cloned from rice (Oryza sativa L.), encodes a receptor-like kinase and confers broad spectrum resistance against Xanthomonas oryzae pv. oryzae (Xoo). Xa21 has been transformed into many cultivars by Agrobacterium-msdiaied system , gene bombardment or conventional crossing-breeding. However, the new physiological races of Xoo which can overcome Xa21 have been found in recent years. In addition, Xa21 shows strong disease resistance at adult stage. If the resistance mechanism of Xa21 is known well, it can result in direct influences in manipulating the resistance mediated by Xa21, such as increasing resistance and expanding resistance spectrum of rice.Using the rice msiterial 4021 including cMyc::Xa21 and the mature protein technologies, SDS-PAGE and western blotting, we improved the conditions of protein extraction from rice leaves and XA21 purification with c-Myc beads, then got the crude protein extracts from leaves and the purified XA21 with high-quality. On the one hand, we detected the changes of expression levels of XA21 which are extracted from the three developmental periods' leaves and the treated leaves respectively. On the other hand, we screened a specific phospho-threonine antibody to analysis the phosphorylation of XA21 in vivo. From the above-mentioned experiments, we preliminarily discussed the possible resistance mechanism mediated by Xa21. The main experiment results are the following:1. Using two groups of resistant and sensitive rice materials, 4021/TP309 and IRBB21/IR24, we did the expanding experiment of Xoo. The result indicates: within 0.5h after inoculation, Xoo moves 1cm at least from the wounding point to the leaves inside, which provides time clues for sampling inoculated leaves.2. The c-Myc beads can purify XA21 well and get rid of non-specific strips detected by c-Myc antibody.3. During the growing process of rice, the protein XA21 is expressed constitutively, and the quantity changes of its degrading protein, XA21_d, are undetectable.4. The quantity changes of XA21 or XA21_d extracted from the inoculated or wounded rice leaves are undetectable.5. Phospho-threonine antibody can detect the phosphorylated kinases with high sensitivity and c-Myc antibody can quantify XA21 protein, so the combination of thec-Myc and P-Thr antibodies can effectively detect the phosphorylation of XA21 in vivo.