[Improvement of nitrogen fixation efficiency and plasmid stability in Bradyrhizobium japonicum by the introduction of dctABD and parCBA/DE genes]

Abstract

A recombinant plasmid pHN207 containing C4-dicarboxylic acid transport genes (dctABD) from Sinorhizobium meliloti, parCBA/DE genes from pTR102 and reporter genes luxAB from pDB30 was constructed by using pLAFR3 as the vector. The pHN207 was then introduced into the Bradyrhizobium japonicum TA11 and CB1809 by bi-parental mating. It was confirmed that parCBA/DE genes could increase the stability of pLAFR3 in the transconjugants under both free-living and symbiotic condition. The results of plant pot experiment indicated that the introduction of dctABD genes could significantly improve the symbiotic nitrogen fixation efficiency of TA11 and CB1809 with soybean varieties of Heilong 33, Ningzhen No. 1 and Yudou No. 1. Compared with the control, the shoot dry weight (biomass) and total nitrogen content of the plants tested were significantly increased.