CAJ | 학술논문

细菌性果斑病(Bacterial Fruit Blotch,BFB)是西瓜和甜瓜的重要病害.本实验从发病甜瓜果实上分离得到致病菌株MH21,经鉴定为燕麦食酸菌西瓜亚种(Acidovorax avenae subsp.citrulli).利用转座子Mini-Tn5构建MH21菌株的突变体库,Southern印迹杂交结果显示Mini-Tn5在菌株MH21染色体上可随机、单拷贝插入.通过浸种处理甜瓜种子进行突变体的致病性检查,筛选得到1株致病性完全丧失的突变体M543.对M543中转座子插入基因的克隆和测序表明其突变基因为燕麦食酸菌Ⅲ型分泌系统(TTSS)中的保守基因hrcR.推测菌株MH21中hrcR基因编码的蛋白定位于细菌内膜,是分泌通道主要成分之一.hrcR基因互补菌株的致病性检查结果显示其致病力恢复到野生型的84%.研究同时发现hrcR基因突变后MH21菌株丧失了在娴草上诱导过敏性坏死反应的能力.本研究从遗传学角度说明TTSS是西甜瓜果斑病菌致病性的重要因子.
세균성과반병(Bacterial Fruit Blotch,BFB)시서과화첨과적중요병해.본실험종발병첨과과실상분리득도치병균주MH21,경감정위연맥식산균서과아충(Acidovorax avenae subsp.citrulli).이용전좌자Mini-Tn5구건MH21균주적돌변체고,Southern인적잡교결과현시Mini-Tn5재균주MH21염색체상가수궤、단고패삽입.통과침충처리첨과충자진행돌변체적치병성검사,사선득도1주치병성완전상실적돌변체M543.대M543중전좌자삽입기인적극륭화측서표명기돌변기인위연맥식산균Ⅲ형분비계통(TTSS)중적보수기인hrcR.추측균주MH21중hrcR기인편마적단백정위우세균내막,시분비통도주요성분지일.hrcR기인호보균주적치병성검사결과현시기치병력회복도야생형적84%.연구동시발현hrcR기인돌변후MH21균주상실료재한초상유도과민성배사반응적능력.본연구종유전학각도설명TTSS시서첨과과반병균치병성적중요인자.
The Bacterial Fruit Blotch (BFB) caused by Acidovorax avenae subsp. citrulli is a serious disease on watermelon and melon. A strain MH21 was isolated from a diseased melon fruit, and was identified as A. ave-nae subsp. citrulli. In this study, the strain MH21 was mutated using transposon Mini-Tn5 to select the mu-tants defective in their pathogencity on melon seedling. Southern blot analysis revealed that transposon Tn5 generated the random and single-copy insertions in the chromosome of strain MH21. A mutant M543 lost its pathogenicity on melon seedling was selected and the gene disrupted by Tn5 was identified to be the homolog of hrcR gene, which coded a conserved inner-membrane protein of Type Ⅲ secretion system (TTSS) in some well-documented bacterial pathogens. The pot experiments revealed that pathogenicity of M543 could be com-plemented by plasmid-born wide-type hrcR gene. Additionally, mutant M543 defective in hrcR gene also lost its ability to trigger hypersensitive reaction (HR) on tobacco leaf. The genetics evidence in this report demon-strated that the TTSS is critical for the pathogenicity of A. avenae subsp. citrulli on melon.