水稻白叶枯病菌PXO99^A无毒基因缺失突变的研究

Studies on the mutant avr genes of Xanthomonas oryzae pv. oryzae PXO99~A by knock-out mutagenesis

对同源重组获得的水稻白叶枯病菌PXO99A菌株的无毒基因突变体PXO99Δavr进行Southern杂交验证、突变序列分析和致病性测定。结果表明:该突变体缺失了5个无毒基因,同源重组发生在PXO99A全基因组中一个有5个无毒基因串联的位点上;与PXO99A相比,突变体在IRBB10等15个水稻品种上引致的病斑明显缩短,而在IRBB14、IRBB21和IRBB55上的病斑则变长;缺失的5个无毒基因的综合表现为毒性因子功能。推断:在缺失的基因中含有无毒基因avrXa14、avrXa21、avrxa13以及与抗病基因Xa3、Xa4、xa5、Xa10、Xa17亲和互作有关的毒性因子。

PXO99Δavr,an avr gene deletion mutant of Xanthomonas oryzae pv.oryzae strain PXO99A was obtained by homologous recombination.The mutant was identified by PCR,Southern blot,flanking sequence analysis and rice inoculation assay.The results showed that five avr genes were deleted in PXO99Δavr and the site directed mutagenesis occurred on the one loci of the five series-wound avr genes in PXO99A genome.The inoculation assays of 36 rice varieties indicated that PXO99Δavr induced shorter lesion on 15 varieties such as IRBB10 and longer lesion on IRBB14,IRBB21,and IRBB55 than PXO99A.Based on the compositive result,five knock-outed avr genes in PXO99A could code virulence factors to induce rice leaf lesion.It was concluded that avr genes avrXa14,avrXa21,avrxa13 could be contained in five series-wound avr genes and some pathogenic fitness factors in PXO99A could be associated with the interaction with rice R genes such as Xa3,Xa4,Xa5,Xa10,Xa17.