华癸根瘤菌7653R hfq基因突变株的构建及其生物学特性

Mutant construction and characterization of hfq in Mesorhizobium huakuii 7653R

【目的】研究hfq基因在Mesorhizobium huakuii 7653R抵抗外界不利环境和共生固氮中的功能特性。【方法】利用pK19mob同源重组方法构建7653R hfq基因的插入失活突变株7653RΔhfq,并构建互补菌株7653RΔhfq-C,对hfq在压力胁迫和共生固氮中的功能特性进行研究。【结果】与野生型7653R相比,突变株7653RΔhfq的生长速率降低,热激处理后致死率升高;hfq突变影响了7653R中部分sRNA的表达;在4.5%乙醇和50 mmol H_2O_2生长胁迫下,突变株适应性明显较野生型差。另外,接种突变株的紫云英结瘤能力和固氮酶活性都明显降低。【结论】hfq基因作为重要的转录后调控因子,在7653R抵御外界胁迫环境和与宿主紫云英的共生固氮中发挥了重要作用。

[Objective] We studied the functions and characteristics of hfq gene in Mesorhizobium huakuii 7653R in adverse environment and symbiotic with its host plant. [Methods] The hfq mutant of 7653R was constructed via homologous recombination with small cloned fragments on suicide plasmids pK19 mob 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. [Results] 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 H_2O_2. 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. [Conclusion] 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.