Truncated betB2-144 plays a critical role in Sinorhizobium meliloti Rm2011 osmoprotection and glycine-betaine catabolism

► BetB2 is related to BetB, the major S. meliloti betaine aldehyde dehydrogenase. ► A truncated version of BetB2, BetB2-144, affects S. meliloti salt resistance. ► BetB2-144 stimulates BADH activity and glycine-betaine (GB) catabolism. ► BetB2-144 lowers GB accumulation, preventing use of GB as an osmoprotectant. ► BetB2-144 affects Rm2011's ability to promote alfalfa survival under salt stress.