Systemic Induction Of Several Defense Enzymes In Suspension-Cultured Cells Of Rice With Zhongshengmycin

Zhongshengmycin is a new promising and commercially available agricultural antibiotic. However the mode of action of Zhongshengmycin was not completely understood at present.The systematic dynamic characteristics of pexoxidase(POD) and its isozyme, polypheno! oxidase(PPO) and its isozyme, phenylalanine ammonnialyase(PAL) were studied in suspension-cultured cells of the near-isogenic lines for bacterial blight resistance of rice which were inoculated with Xanthomonas oryzae and treated with different concentrations of Zhongshengmycin. The results are listed as follow:(1) A system of callus induction from mature rice seeds and suspension culture of the near-isogenic lines for bacterial blight resistance of rice cells were set up.(2) Systemic induction of several defense enzymes in suspension-cultured cells of rice inoculated with Xanthomonas oryzae pv. oryzae and Zhongshengmycin was determined. After being treated with Xanthomonas oryzae and Zhongshengmycin, the activity of POD, PPO, PAL in suspension-cultured cells of rice were higher than the control. The results indicated that Zhongshengmycin can induce the expression of these defense enzymes respectively in suspension-cultured cells of rice. For POD , the optimum concentration of Zhongshengmycin is 15mg/l. However, for PPO and PAL, the optimum concentration of Zhongshengmycin is 10mg/l; and the induction of POD, PAL expression in susceptible rice cultivar Shennong 1033 was generally lower than in resistant rice cultivar CBB4, but the induction of PPO expression in CBB4 was generally lower than in Shennong 1033. The results showed that the induction of POD, PPO, PAL expression in suspension-cultured cells of rice was positively related to rice resistance to bacterial blight disease, and could be used as the indicators of rice resistance to bacterial blight disease.(3) Electrophoretic isozyme zymogram patterns of POD, PPO in suspension-cultured cells of rice treated with Xanthomonas oryzae and with Zhongshengmycin were studied. After inoculation with Xanthomonas oryzae, the systematiec dynamic characteristics of POD and PPO isozyme were determined. The results demonstrated that Zhongshengmycin can induce the expression of POD, PPO in suspension-cultured cells of rice, which were identified by the thickening of the original isozyme bands and the expression of some new isozyme bands.And these changed bands were related to a marked increase of the over-all enzyme activity.This thesis could not only help us to understand the mode of action of Zhongshengmycin, but also provide information for the method of screening new bactericides.