含hrp基因的克隆片段在水稻白叶枯病菌不同小种中的功能和同源性

 将从水稻白叶枯病菌(Xanthomonas campestris pv.oryzae Dye,简称Xco)小种3菌株JXOⅢ中克隆的hrp基因片段(pNAX3103),用三亲交配法向病菌其它小种及其毒性基因突变体转移,结果表明pNAX3103可以进入其它小种,但对不同小种毒性基因突变体的转移能力则不同。功能互补分析表明;该hrp基因片段在不同小种中对病菌的生长,以及蛋白酶、果胶酶和纤维素酶的产生和分泌无明显影响;在野生型菌株中能增加亲本菌株对水稻品种IR26的致病力(JXO I)或亲和性(JXO V),对于毒性基因突变体,pNAX3103虽能进入JXO I经Tn5诱变的毒性基因突变体XcoM1107,但不能恢复其致病性和淀粉酶阴性反应。用hrp基因片段作为探针,对10个来源不同的小种或菌系群进行DNA同源性分析,结果与所有Xco菌株都有明显的同源性杂交带,但杂交带型不同,与甘蓝黑腐病菌、水稻细菌性条斑病菌、柑桔溃疡病菌、大白菜。软腐病菌的DNA有同源杂交带,但与水稻基腐病菌DNA无同源性。

FUNCTION AND HOMOLOGY OF hrp GENE REGION WITHIN DIFFERENT RACES OF XANTHOMONAS CAMPESTRIS PV. ORYZAE

A recombinant cosmid (pNAX3103) containing hrp gene region from Xanthomonas campestris pv. oryzae race 3 (JXO Ⅲ) was transferred to different raceS. Their virulent gene mutants by triparent mating, and pNAX3103 could be introduced into different races but not to their mutants. The fuction analysis revealed that hrp gene region in pNAX3103 had no obvious effect on the growth, the production and excretion of protease, pectase and cellulase in different races of pathogen, and it could enhance the virulence of race 1 (JXO I) and change the compatibility of race 5(JXO V) on rice cultivar IR26. When the mutants were tested pNAX3103 could npt be introduced into mutants XcoM5102, XcoM5103 of race 5 (JXO V) and complemented mutant XcoM1107 of race 1(JXO I) not to restore the phenotypes of the pathogenicity and amylase activity as wildtype strain (JXO I). The DNA homology of 10 strains of different races Xco and 4 of phytopathogenic bacteria were analyzed by pNAX3103 as a probe. Homologous hybridization bands were found in all tested strains of Xco, and also in X. c. pv. campestris, X. c. pv. oryzacola, X. c. pv. citri, and Erwinia carotovora var. carotovora, but not in the strain of E. chrysanthemi.