摘要瓜类细菌性果斑病(bacterial fruit blotch of watermelon, BFB)是近年来发生在西瓜、甜瓜等葫芦科(Cucurbitaceae)植物上的重要细菌病害，由西瓜噬酸菌(Acidovorax citrulli, Ac)引起。本研究以xjL12菌株为背景构建了转座子(Tn5)插入文库。通过注射接种哈密瓜(Cucumis melo var. saccharinus)子叶和烟草叶片进行突变体的筛选，得到1株致病性完全丧失并失去激发烟草过敏反应的突变体△xj48。对△xj48中转座子插入基因的克隆和测序表明其突变基因为西瓜噬酸菌Ⅲ型分泌系统(T3SS)中的保守基因hpaP。利用基因重组技术构建了hpaP基因的突变体，发现hpaP突变后影响了xjL12菌株的游动性、生物膜的形成能力及hrcV基因的表达。hpaP基因的互补菌株部分恢复其致病力。本研究证实了果斑病菌中的hpaP基因与该细菌的致病力相关，在侵染瓜类作物的过程中起着不可缺失的作用。
Abstract：Acidovorax citrulli (Ac) is the causal agent of bacterial fruit blotch (BFB), a disease affecting watermelon, melon and other cucurbits. A transposon (Tn5) mutant library was constructed with strain xjL12. The mutant △xj48 was selected for its loss of pathogenicity on hami melon (Cucumis melo var. saccharinus) seedlings and its ability to elicit hypersensitive reaction (HR) on tobacco. The gene disrupted by Tn5 was identified as a homolog of the hpaP gene, a conserved gene of type Ⅲ secretion system (T3SS). Further characterization of the mutant using genetic recombination revealed that swimming motility, biofilm formation and the expression of the hrcV gene requires a functional hpaP gene. Pathogenicity was partially recovered in a hpaP complemented strain. The genetic evidence in this report demonstrates that the hpaP gene is critical for the pathogenicity of Acidovorax citrulli, and plays an important role in infection.
