Pseudomonas syringae pv. tabaci 6605 (Pta6605) is a causal agent of wildfire disease in host tobacco plants and is highly motile. Pta6605 has multiple clusters of chemotaxis genes including cheA, a gene encoding a histidine kinase, cheY, a gene encoding a response regulator, mcp, a gene for a methyl-accepting chemotaxis protein, as well as flagellar and pili biogenesis genes. However, only two major chemotaxis gene clusters, cluster I and cluster II, possess cheA and cheY. Deletion mutants of cheA or cheY were constructed to evaluate their possible role in Pta6605 chemotaxis and virulence. Motility tests and a chemotaxis assay to known attractant demonstrated that cheA2 and cheY2 mutants were unable to swarm and to perform chemotaxis, whereas cheA1 and cheY1 mutants retained chemotaxis ability almost equal to that of the wild-type (WT) strain. Although WT and cheY1 mutants of Pta6605 caused severe disease symptoms on host tobacco leaves, the cheA2 and cheY2 mutants did not, and symptom development with cheA1 depended on the inoculation method. These results indicate that chemotaxis genes located in cluster II are required for optimal chemotaxis and host plant infection by Pta6605 and that cluster I may partially contribute to these phenotypes.

丁香假单胞菌PV。Tabaci 6605（Pta 6605）是寄主烟草植物中野火病的病原体，具有很高的运动力。Pta 6605具有多个趋化性基因簇，包括cheA，编码组氨酸激酶的基因，cheY，编码响应调节剂的基因，mcp，甲基接受趋化性蛋白的基因，以及鞭毛和菌毛生物发生基因。然而，只有两个主要的趋化性基因簇，簇I和簇II，具有cheA和cheY。构建了cheA或cheY的缺失突变体，以评估其可能在Pta 6605趋化性和毒力。运动性测试和对已知引诱剂的趋化性测定表明，cheA2和cheY2突变体无法蜂拥而至，无法进行趋化性，而cheA1和cheY1突变体保留的趋化性几乎与野生型（WT）菌株相同。虽然WT和cheY1的突变PTA 6605造成了主机烟叶严重的疾病的症状，在cheA2和cheY2突变体也没了，症状发展与cheA1取决于接种方法。这些结果表明位于群集II中的趋化性基因是Pta 6605最佳趋化性和宿主植物感染所必需的，并且群集I可能部分地促进了这些表型。