Symbiotic activity of alfalfa rhizobia (Sinorhizobium meliloti) strains with genetically modified transport of dicarboxylic acids

Abstract

Inactivation of the genes involved in dicarboxylic acid transport in the alfalfa rhizobia Sinorhizobium meliloti—the structural gene of succinate permease dctA and its transcriptional regulators dctBD, nifA, and ntrA—leads to complete or partial loss of N2-fixing activity, while amplification of these genes leads to an increase in this activity. This considerably elevates the accumulation of nitrogen and carbon in alfalfa; however, the plant weight increases to a lesser degree, which is associated with an incomplete translocation of nitrogen to the aboveground organs. Factor analysis has demonstrated that the amplification of dctABD genes significantly influences these characteristics of symbiotic efficiency in all the performed experiments, while the effects of dctA, nifA, and ntrA depend on the plant cultivar and vegetation conditions.