Graduate School of Environmental and Life Science, Okayama University.
The United Graduate School of Agricultural Science, Gifu University.
Microbes Environ. 2022;37(1). doi: 10.1264/jsme2.ME21076.
Pseudomonas syringae pv. tabaci 6605 (Pta6605) is a foliar plant pathogen that causes wildfire disease on tobacco plants. It requires chemotaxis to enter plants and establish infection. While chemotactic signals appear to be the main mechanism by which Pta6605 performs directional movement, the involvement of aerotaxis or energy taxis by this foliar pathogen is currently unknown. Based on domain structures and similarity with more than 50 previously identified putative methyl-accepting chemotaxis proteins (MCPs), the genome of Pta6605 encodes three potential aerotaxis transducers. We identified AerA as the main aerotaxis transducer and found that it possesses a taxis-to-serine-and-repellent (Tsr)-like domain structure that supports a periplasmic 4HB-type ligand-binding domain (LBD). The secondary aerotaxis transducer, AerB, possesses a cytosolic PAS-type LBD, similar to the Aer of Escherichia coli and Pseudomonas aeruginosa. Aerotaxis ability by single and double mutant strains of aerA and aerB was weaker than that by wild-type Pta6605. On the other hand, another cytosolic PAS-type LBD containing MCP did not make a major contribution to Pta6605 aerotaxis in our assay system. Furthermore, mutations in aerotaxis transducer genes did not affect surface motility or chemotactic attraction to yeast extract. Single and double mutant strains of aerA and aerB showed less colonization in the early stage of host plant infection and lower biofilm production than wild-type Pta6605. These results demonstrate the presence of aerotaxis transducers and their contribution to host plant infection by Pta6605.
丁香假单胞菌 pv. 番茄（Pta6605）是一种叶部植物病原体，可引起烟草野火病。它需要趋化作用进入植物并建立感染。虽然趋化信号似乎是 Pta6605 进行定向运动的主要机制，但这种叶部病原体是否涉及趋化性或能量趋化性目前尚不清楚。根据结构域和与 50 多个先前鉴定的假定甲基接受趋化性蛋白（MCP）的相似性，Pta6605 的基因组编码三个潜在的趋化性转导蛋白。我们鉴定出 AerA 为主要的趋化性转导蛋白，并发现它具有趋化性到丝氨酸和排斥（Tsr）样结构域结构，支持周质 4HB 型配体结合域（LBD）。次要的趋化性转导蛋白 AerB 具有细胞质 PAS 型 LBD，类似于大肠杆菌和铜绿假单胞菌的 Aer。aerA 和 aerB 的单突变和双突变株的趋化性能力弱于野生型 Pta6605。另一方面，我们的检测系统中，另一个含有 MCP 的细胞质 PAS 型 LBD 对 Pta6605 的趋化性没有做出主要贡献。此外，趋化性转导基因的突变并不影响表面迁移性或对酵母提取物的趋化性吸引力。aerA 和 aerB 的单突变和双突变株在宿主植物感染的早期阶段定植能力较弱，生物膜生成量也低于野生型 Pta6605。这些结果表明存在趋化性转导蛋白，它们对 Pta6605 感染宿主植物有贡献。
