The symbiotic N2-fixation process (SNF) in the legume-rhizobia interaction, relevant for sustainable agriculture, is a complex process that is tightly regulated in both symbionts. For several years our group has analyzed the SNF between common bean (Phaseolus vulgaris) -the most important legume for human consumption, worldwide- and Rhizobium etli. Despite the agronomical importance of the common bean, the genomics/genetic research and knowledge of common bean SNF remains scant. Through reverse genetic approaches, our group has contributed to decipher novel global regulators -transcription factors and microRNAs- demonstrating their role and relevance in the SNF. Analysis of symbiotic mutants, mainly from the model legumes, has been instrumental for the understanding of legume symbiotic genes. However, to date, only one common bean symbiotic mutant has been genetic and molecularly characterized. On this basis, current research from our group includes the characterization of three symbiotic (non-nodulating) mutants selected from an EMS-generated common bean (BAT 93) mutant population. Our analysis has revealed that each mutant is altered in a different early step of the rhizobial infection process. The whole genome sequence analysis approach led to predict candidate mutated genes for each mutant. Advances on the demonstration of the responsible mutated gene in each line and about its role and relevance in the SNF process, will be presented.
