水稻白叶枯病菌(Xanthomonas oryzae pv.oryzae)化学诱变hrp基因突变体及相关性状的研究

 硫酸二乙酯(diethyl sulfate,DES)化学诱变水稻白叶枯病菌(Xanthomonas oryzae pv.oryzae,Xoo)日本系统III号小种(JXOIII),获得16株hrp-突变体,其在感病寄主水稻IR26、汕优63上失去致病性和在非寄主烟草上失去过敏反应。所得的hrp-突变体并无黄色素缺失现象。16株hrp-突变体的淀粉酶、果胶酶、蛋白酶、纤维素酶和脂酶等胞外酶活性基本与野生型一致。JCM2092、JCM2211、JCM2252和JCM2457这4株hrp-突变体为III型泌出通道突变体,JCM0066等另12株hrp-突变体的超声波破碎液、离心上清液中无激发HR的信号物质存在。细胞组分分析表明,激发烟草HR的信号物质不是LPS而是蛋白类物质。来自JXOIII基因文库hrp基因克隆pUHRX245中的1.1kb SacI-KpnI片段,能够互补hrp-突变体JCM0066和JCM2482,使其恢复在烟草上激发HR的能力,但不能恢复其致病性。

PATHOLOGICAL AND BIOCHEMICAL CHARACTERISTICS OF hrp- MUTANTS PRODUCED BY CHEMICAL MUTAGENESIS FROM Xanthomonas oryzae pv. oryzae

16 strains of hrp-mutants were obtained from wild type JXOⅢ of Xanthomonas oryzae pv. oryzae (Xoo) by using diethyl sulfate (DES) as a mutagenic chemical. All the mutants lost their pathogenicity on susceptible rice, IR26 and Shanyou 63, and were unable to trigger hypersensitive response (HR) on nonhost plant, tobacco. The obtained hrp-mutants did not show xanthomonadin deficiency. Extracellular enzyme (amylase,pectase lyase,protease,cellulase and lipase) activities of all the hrp-mutants were similar to those of the wild type.The composition analyse of the pathogenic bacteria demonstrated that lipopolysaccharide (LPS) is not the signal substance to induce HR on tobacco. Four hrp-mutants, JCM2092,JCM2211,JCM2252 and JCM2457, were due to mutagenesis in the type Ⅲ secretion pathway while other 12 hrp-mutants were not since the substance triggering HR on tobacco was not detected in their sonicated cells and supernatants. 1.1 kb SacI KpnI fragment from hrp gene clone, pUHRX245, from JXOⅢ gene library can restore the ability of HR elicitation on tobacco to hrp-mutants, JCM0066 and JCM2482, but not the pathogenicity to hrp-mutants.