Genomic alternatives for nodulation and nitrogen fixation in common bean Phaseolus vulgaris

V. GONZÁLEZ; R.I. SANTAMARÍA; P. BUSTIS; FABIOLA MIRANDA; DIANA GALLEGO; GONZALO A. TORRES TEJERIZO; LUIS LOZANO; O.M. PÉREZ-CARRASCAL; S. JUAREZ; MARCO A. ROGEL-HERNÁNDEZ; J. L. ACOSTA; ERNESTO ORMEÑO-ORRILLO; ESPERANZA MARTINEZ-ROMERO; MIGUEL ANGEL CEVALLOS; DAVID ROMERO; PABLO VINUESA; SUSANA BROM

Conferencia; 11th European Nitrogen Fixation Conference; 2014

Symbiotic nitrogen fixation of rhizobia with species of leguminous plants is widespread in nature. The promiscuos nature of common bean (Phaseolus vulgaris) hosting different species rhizobial species is known. R. etli, R. phaseoli, R. tropicii, R. gallicum, R. giardinii, and several other species (1) have been reported as P. vulgaris nodule bacteria. Complete genomes from some of them are available (2,4, 5) and genome comparisons have led the reevaluation of the taxonomic status of the Rhizobium species that nodulate bean (3). To understand the genomic alternatives to perform symbiosis with common bean, we determined the genome sequences of other rhizobial species and strains, which have the common property of forming nodules in bean. Here, we report the complete genome sequences of R. gallicum R602 and IE4872, Sinorhizobium fredii GR64, R. leucaenae NXC24, Sinorhizobium americanum NXT3, and the R. etli strains IE4771, IE4803, NXC12 and NXC14. These genomic sequences, with others previously reported (2, 4, 5), allowed us to make an extended comparison of the core and accessory components, as well as to infer their common content involved in P. vulgaris nodulation. Our analysis has revealed different alternative symbiotic gene sets to nodulate and fix nitrogen in bean. We observed that the different lineages of Rhizobium etli contain pSym plasmids with different degrees of conservation. We suggest that a particular type of pSym (phaseoli) common to R. etli and R. phaseoli is of recent origin, in contrast to the pSyms of other symbiovarieties and species