Oligopeptide uptake improves oxidative stress resistance and nodulation competitiveness in soybean rhizobia

Abstract

We here explored the mechanisms associated with oxidative stress resistance and root colonization by soybean rhizobia. Genomic and physiological analyses supported the fact that the mutation of a highly conserved valine at position 263 to alanine in an aspartate kinase-like protein associated with oligopeptide uptake (LysC) enhances the oxidative stress resistance of the commercial inoculant Bradyrhizobium japonicum E109. Integrated genetic and physiological studies suggest that LysC is part of a conserved substrate transport system in Bradyrhizobium, and that the LysC-V263A mutation in strain E109 significantly increased its oligopeptide uptake, survival during periods of starvation and nodulation competitiveness. Finally, the potential utilization of the CRISPR system to promptly propagate this gain-of-function mutation in soybean production worldwide is discussed.