title: Identification and characterization of chemosensors for d-malate, unnatural enantiomer of malate, in Ralstonia pseudosolanacearum.
abstract: Ralstonia pseudosolanacearum Ps29 is attracted by nonmetabolizable d-malate, an unnatural enantiomer. Screening of a complete collection of single-mcp-gene deletion mutants of Ps29 revealed that the RSc1156 homologue is a chemosensor for d-malate. An RSc1156 homologue deletion mutant of Ps29 showed decreased but significant responses to d-malate, suggesting the existence of another d-malate chemosensor. McpM previously had been identified as a chemosensor for l-malate. We constructed an RSc1156 homologue mcpM double deletion mutant and noted that this mutant failed to respond to d-malate; thus, the RSc1156 homologue and McpM are the major chemosensors for d-malate in this organism. To further characterize the ligand specificities of the RSc1156 homologue and McpM, we constructed a Ps29 derivative (designated K18) harbouring deletions in 18 individual mcp genes, including mcpM and RSc1156. K18 harbouring the RSc1156 homologue responded strongly to l-tartrate and d-malate and moderately to d-tartrate, but not to l-malate or succinate. K18 harbouring mcpM responded strongly to l-malate and d-tartrate and moderately to succinate, fumarate and d-malate. Ps29 utilizes l-malate and l-tartrate, but not d-malate. We therefore concluded that l-tartrate and l-malate are natural ligands of the RSc1156 homologue and McpM, respectively, and that chemotaxis toward d-malate is a fortuitous response by the RSc1156 homologue and McpM in Ps29. We propose re-designation of the RSc1156 homologue as McpT. In tomato plant infection assays, the mcpT deletion mutant of highly virulent R. pseudosolanacearum MAFF106611 was as infectious as wild-type MAFF106611, suggesting that McpT-mediated chemotaxis does not play an important role in tomato plant infection.
authors.affiliation: Department of Molecular Biotechnology, Graduate School of Advanced Sciences of Matter, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8530, Japan.
authors.forename: Mattana
authors.initials: M
authors.lastname: Tunchai
authors.affiliation: Department of Molecular Biotechnology, Graduate School of Advanced Sciences of Matter, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8530, Japan.
authors.forename: Akiko
authors.initials: A
authors.lastname: Hida
authors.affiliation: Department of Molecular Biotechnology, Graduate School of Advanced Sciences of Matter, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8530, Japan.
authors.forename: Shota
authors.initials: S
authors.lastname: Oku
authors.affiliation: Department of Molecular Biotechnology, Graduate School of Advanced Sciences of Matter, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8530, Japan.
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Nakashimada
authors.affiliation: Department of Molecular Biotechnology, Graduate School of Advanced Sciences of Matter, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8530, Japan.
authors.forename: Takahisa
authors.initials: T
authors.lastname: Tajima
authors.affiliation: Department of Molecular Biotechnology, Graduate School of Advanced Sciences of Matter, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8530, Japan.
authors.forename: Junichi
authors.initials: J
authors.lastname: Kato
mesh_terms: D002633:Chemotaxis / Q000235:genetics / Q000502:physiology*; D017353:Gene Deletion; D018551:Solanum lycopersicum / Q000382:microbiology; D008293:Malates / Q000378:metabolism*; D010935:Plant Diseases / Q000382:microbiology; D043367:Ralstonia / Q000145:classification / Q000378:metabolism* / Q000472:pathogenicity; D013237:Stereoisomerism; D019802:Succinic Acid / Q000378:metabolism; D013644:Tartrates / Q000378:metabolism*
chemical_list: D008293:Malates; D013644:Tartrates; D019802:Succinic Acid; C029768:tartaric acid