title: The plant growth-promoting bacteria Azospirillum amazonense: genomic versatility and phytohormone pathway.
abstract: The rhizosphere bacterium Azospirillum amazonense associates with plant roots to promote plant growth. Variation in replicon numbers and rearrangements is common among Azospirillum strains, and characterization of these naturally occurring differences can improve our understanding of genome evolution. We performed an in silico comparative genomic analysis to understand the genomic plasticity of A. amazonense. The number of A. amazonense-specific coding sequences was similar when compared with the six closely related bacteria regarding belonging or not to the Azospirillum genus. Our results suggest that the versatile gene repertoire found in A. amazonense genome could have been acquired from distantly related bacteria from horizontal transfer. Furthermore, the identification of coding sequence related to phytohormone production, such as flavin-monooxygenase and aldehyde oxidase, is likely to represent the tryptophan-dependent TAM pathway for auxin production in this bacterium. Moreover, the presence of the coding sequence for nitrilase indicates the presence of the alternative route that uses IAN as an intermediate for auxin synthesis, but it remains to be established whether the IAN pathway is the Trp-independent route. Future investigations are necessary to support the hypothesis that its genomic structure has evolved to meet the requirement for adaptation to the rhizosphere and interaction with host plants.
authors: Centro de Biotecnologia, Laboratório de Microrganismos Diazotróficos, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS, Brazil.
authors: Ricardo
authors: R
authors: Cecagno
authors: Centro de Biotecnologia, Laboratório de Microrganismos Diazotróficos, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS, Brazil.
authors: Tiago Ebert
authors: TE
authors: Fritsch
authors: Centro de Biotecnologia, Laboratório de Microrganismos Diazotróficos, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS, Brazil ; Departamento de Biologia Molecular e Biotecnologia, Instituto de Biociências, Universidade Federal do Rio Grande do Sul (UFRGS), CP 15005, 91501-970 Porto Alegre, RS, Brazil.
authors: Irene Silveira
authors: IS
authors: Schrank
mesh_terms: D016949:Azospirillum / Q000235:genetics / Q000378:metabolism; D022761:Gene Transfer, Horizontal; D014644:Genetic Variation; D007210:Indoleacetic Acids / Q000378:metabolism*; D010937:Plant Growth Regulators / Q000096:biosynthesis / Q000235:genetics; D027343:Rhizome / Q000235:genetics / Q000378:metabolism
chemical_list: D007210:Indoleacetic Acids; D010937:Plant Growth Regulators