Suppression of Nodule Formation by RNAi Knock-Down of in .

Background/objectives: The balanced regulation of innate immunity plays essential roles in rhizobial infection and the establishment and maintenance of symbiosis. The evolutionarily conserved cell death suppressor Bax inhibitor-1 plays dual roles in nodule symbiosis, providing a valuable clue in balancing immunity and symbiosis, while it remains largely unexplored in the legume .

Methods/results: In the present report, the gene family of was identified and characterized. We identified 6 genes that translate into peptides containing 240-255 amino acids with different structural characteristics and isoelectric points. We performed phylogenetic analyses and detected evolutionary conservation and divergence among BI-1 proteins from , , , , and . Expression profiles among different roots indicated that the inoculation of MAFF303099 significantly increased the expression of most of the BI-1 family genes. We down-regulated the transcripts of by RNA interference and observed that promotes nodulation and nodule formation.

Conclusions: These discoveries shed light on the functions of genes in , and simultaneously emphasize the potential application of in enhancing the symbiotic nitrogen fixation ability of legumes.