Studies on pathoigenicity mechanism of Ralstonia solanacearum and disease development of bacterial wilt

青枯雷尔氏菌OE 1 -1（Ralstonia solanacearum OE 1 -1）是烟草的致病菌。OE 1 -1的突变体Tn 4431，31 b通过浸根法接种烟草后，在烟草的维管束中生长并移动，但对烟草的致病性丧失。但该突变体对通过切段接种到烟草维管束中的植株表现出致病性。31 b突变的PopA蛋白由319个氨基酸残基组成，1-307个氨基酸残基的氨基酸序列与OE 1 -1的PopA蛋白的氨基酸序列相同。OE 1 -1的popABC操纵子缺失突变株△ABC-OE的致病性与亲本菌株相似。另一方面，△ABC-OE与p31 b（包括突变的popA）的混合物△ OE-p31 b表现出与31 b相似的致病性。RT-PCR分析表明，OE 1 -1中的popA基因在入叶后3 h（HIT）表达，而31 b和△ OE-p31 b中的突变体popA基因在入叶后3 h（HIT）表达。当OE 1 -1的一个子集 ...更多信息 将含有popA的pPapa与组成型活性启动子融合，渗入烟草叶片中，表达popA 1 HAI。浸根法接种后，Papa在接种区不生长，向周围移动，导致Papa对烟草的致病性丧失。而Papa直接接种于维管束后仍保持致病性。这些结果表明，PopA蛋白不直接参与细菌的致病性，因为popA直到3 HAI才表达。然而，当PopA表达1HAI时，PopA可以在宿主植物中作为细菌增殖的负效应物，导致细菌致病性的丧失。此外，C-末端突变的PopA蛋白影响了从3 HAI到细菌到达维管束的细菌-植物相互作用，从而对细菌的致病性产生负调控作用。综上所述，病原菌侵染后3 h内的增殖和向维管束内的移动是病原菌致病性的重要因素，而病原菌侵染后3 h内与寄主植物之间的相互作用是病原菌致病性的重要因素。病原菌侵染后3 h内，病原菌在寄主植物根和叶肉细胞间隙中的相互作用是病原菌致病性的重要因素。少

Ralstonia solanacearum OE1-1 (OE1-1) is pathogenic to tobacco. A popA-mutant of OE1-1 with Tn4431, 31b, grew in and moved through vascular bundle in tabacco but lost its pathogenicity to the tobacco plants, when inoculated by root dipping and infiltrated into tobacco leaves. However, the mutant showed pathogenicity to the tobacco plants inoculated into vascular bundle through cut stems. The mutated PopA protein of 31b was composed of 319 amino acid residues, and the amino acid sequence of 1-307 residues was identical to that of PopA protein of OE1-1. A popABC operon-deleted mutant of OE1-1, △ABC-OE, showed pathogenicity similarly as the parent strain. On the other hand, a transformant, △OE-p31b, of △ABC-OE with p31b including a mutated popA showed pathogenicity similarly as 31b. The analysis of RT-PCR showed that popA in OE1-1 was expressed 3 hr after infiltration with into tobacco leaves (HIT), and mutated popA in 31b and △OE-p31b was also expressed 3 HIT. When a transformant of OE1-1 … More , Papa with pPapa containing popA fused to a constitutively active promoter infiltrated into tobacco leaves, popA was expressed 1 HAI. Papa did not grow in inoculated area and move to periphery, resulting in loss of its pathogenicity to tobacco plants when inoculated using the root dipping and infiltrated into tobacco leaves. However, Papa retained its pathogenicity when directly inoculated into vascular bundle. These results indicate that PopA protein is not directly involved in the bacterial pathogenicity because popA is not expressed until 3 HAI. However, when popA is expressed 1 HAI, PopA can function as a negative effector of the bacterial proliferation in the host plants, resulting in loss of the bacterial pathogenicity. Moreover, C-terminus-mutated PopA protein makes influences on the bacteria-plant interactions from 3 HAI to the bacterial arrival to vascular bundle, resulting in negative regulation on the bacterial pathogenicity. Taken together, the bacterial proliferation and movement into vascular bundle immediately after invasion, which are essential factors of its pathogenicity, depend on interactions between R solariacearum and host plants during 3 hr after the bacterial invasion Moreover, development of wilt symptom depends on the interactions in intercellular spaces of roots and mesophyll until the bacterial infection to vascular bundle. Less