[Mutant construction and characterization of hfq in Mesorhizobium huakuii 7653R]

We studied the functions and characteristics of hfq gene in Mesorhizobium huakuii 7653R in adverse environment and symbiotic with its host plant.

The hfq mutant of 7653R was constructed via homologous recombination with small cloned fragments on suicide plasmids pK19mob to insert target gene. We applied 7653RΔhfq to characterize stress tolerance and symbiosis with host plant, in comparison with the complementary strains 7653R △hfq-C and the wild type.

Mutant 7653RΔhfq presented lower growth rate, and higher mortality after heat shock-pretreated than that of the wild type, as well as the decreasing adaptability under the stress of 4.5% ethanol and 50 mmol H2O2. The defection of hfq affected the expression of some sRNAs in 7653R. Moreover, the mutant displayed significant reduced nodulation ability and nitrogenase activity compared with the wild type.

As a crucial post transcriptional regulatory factor, hfq plays an important role in Mesorhizobium Huakuii 7653R on both processes of stress resistance and symbiosis with the host plant Astragalus sinicus L.