title: The rkpU gene of Sinorhizobium fredii HH103 is required for bacterial K-antigen polysaccharide production and for efficient nodulation with soybean but not with cowpea.
abstract: In this work, the role of the rkpU and rkpJ genes in the production of the K-antigen polysaccharides (KPS) and in the symbiotic capacity of Sinorhizobium fredii HH103, a broad host-range rhizobial strain able to nodulate soybean and many other legumes, was studied. The rkpJ- and rkpU-encoded products are orthologous to Escherichia coli proteins involved in capsule export. S. fredii HH103 mutant derivatives were contructed in both genes. To our knowledge, this is the first time that the role of rkpU in KPS production has been studied in rhizobia. Both rkpJ and rkpU mutants were unable to produce KPS. The rkpU derivative also showed alterations in its lipopolysaccharide (LPS). Neither KPS production nor rkpJ and rkpU expression was affected by the presence of the flavonoid genistein. Soybean (Glycine max) plants inoculated with the S. fredii HH103 rkpU and rkpJ mutants showed reduced nodulation and clear symptoms of nitrogen starvation. However, neither the rkpJ nor the rkpU mutants were significantly impaired in their symbiotic interaction with cowpea (Vigna unguiculata). Thus, we demonstrate for the first time to our knowledge the involvement of the rkpU gene in rhizobial KPS production and also show that the symbiotic relevance of the S. fredii HH103 KPS depends on the specific bacterium-legume interaction.
authors.affiliation: Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, Av. Reina Mercedes 6. 41012-Sevilla, Spain.
authors.forename: Ángeles
authors.initials: Á
authors.lastname: Hidalgo
authors.affiliation: Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, Av. Reina Mercedes 6. 41012-Sevilla, Spain.
authors.forename: Isabel
authors.initials: I
authors.lastname: Margaret
authors.affiliation: Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, Av. Reina Mercedes 6. 41012-Sevilla, Spain.
authors.forename: Juan C
authors.initials: JC
authors.lastname: Crespo-Rivas
authors.affiliation: Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, Av. Reina Mercedes 6. 41012-Sevilla, Spain.
authors.forename: Maribel
authors.initials: M
authors.lastname: Parada
authors.affiliation: Departamento de Bioquímica Vegetal y Biología Molecular, Facultad de Biología, Universidad de Sevilla, Av. Reina Mercedes 6. 41012-Sevilla, Spain.
authors.forename: Piedad Del Socorro
authors.initials: PDS
authors.lastname: Murdoch
authors.affiliation: Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, Av. Reina Mercedes 6. 41012-Sevilla, Spain.
authors.forename: Abigail
authors.initials: A
authors.lastname: López
authors.affiliation: Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, Av. Reina Mercedes 6. 41012-Sevilla, Spain.
authors.forename: Ana M
authors.initials: AM
authors.lastname: Buendía-Clavería
authors.affiliation: Departamento de Biología Celular, Facultad de Biología, Universidad de Sevilla, Av. Reina Mercedes 6. 41012-Sevilla, Spain.
authors.forename: Javier
authors.initials: J
authors.lastname: Moreno
authors.affiliation: Departamento de Biotecnología, Escuela Técnica Superior de Ingenieros Agrónomos, and Centro de Biotecnología y Genómica de Plantas (CBGP), Universidad Politécnica de Madrid, Campus de Montegancedo, Carretera M40, Km. 37.7, 28223 Pozuelo de Alarcón, Madrid, Spain.
authors.forename: Marta
authors.initials: M
authors.lastname: Albareda
authors.affiliation: Departamento de Química Orgánica, Facultad de Química, Universidad de Sevilla, Apdo. 553. 41071-Sevilla, Spain.
authors.forename: Antonio M
authors.initials: AM
authors.lastname: Gil-Serrano
authors.affiliation: Departamento de Química Orgánica, Facultad de Química, Universidad de Sevilla, Apdo. 553. 41071-Sevilla, Spain.
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Rodríguez-Carvajal
authors.affiliation: Departamento de Biotecnología, Escuela Técnica Superior de Ingenieros Agrónomos, and Centro de Biotecnología y Genómica de Plantas (CBGP), Universidad Politécnica de Madrid, Campus de Montegancedo, Carretera M40, Km. 37.7, 28223 Pozuelo de Alarcón, Madrid, Spain.
authors.forename: Jose M
authors.initials: JM
authors.lastname: Palacios
authors.affiliation: Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, Av. Reina Mercedes 6. 41012-Sevilla, Spain.
authors.forename: José E
authors.initials: JE
authors.lastname: Ruiz-Sainz
authors.affiliation: Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, Av. Reina Mercedes 6. 41012-Sevilla, Spain.
authors.forename: José M
authors.initials: JM
authors.lastname: Vinardell
mesh_terms: D000942:Antigens, Bacterial / Q000096:biosynthesis; D004269:DNA, Bacterial / Q000235:genetics; D007887:Fabaceae / Q000382:microbiology; D005798:Genes, Bacterial; D005816:Genetic Complementation Test; D019833:Genistein / Q000494:pharmacology; D009154:Mutation; D055170:Plant Root Nodulation; D011135:Polysaccharides, Bacterial / Q000096:biosynthesis*; D042181:Sinorhizobium fredii / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D013025:Glycine max / Q000382:microbiology*; D013045:Species Specificity; D013559:Symbiosis
chemical_list: D000942:Antigens, Bacterial; D004269:DNA, Bacterial; D011135:Polysaccharides, Bacterial; D019833:Genistein