根瘤菌TtsI突变体构建及结瘤表型鉴定

Construction of TtsI mutant of rhizobia and identification of nodulation phenotype

本论文以中华根瘤菌HH103 Ⅲ型分泌系统调控因子TtsI为研究对象,采用三亲杂交的方法获得突变体HH103ΩTtsI,并用PCR鉴定。Ⅲ型效应因子表达分析表明,在染料木苷存在的情况下,TtsI突变能够抑制NopAA、NopD、NopL和NopP等效应因子基因的转录和表达。当TtsI突变情况下,能够显著抑制根瘤菌HH103 Ⅲ型效应因子的合成。用TtsI突变体和野生型根瘤菌HH103对来自不同生态区的10份种质资源进行结瘤鉴定,结果显示,TtsI突变后能够显著减少根瘤平均数和根瘤干重。导入系群体结瘤鉴定结果显示,TtsI突变体显著减少导入系平均瘤数。说明TtsI在大豆-根瘤菌共生体系建立过程中发挥重要的作用,这种作用的发挥有可能是依赖于调控其他Ⅲ型效应因子的表达。

In this study,TtsI,a regulator of HH103 type III secretion system in Sinorhizobium was detected.The mutant HH103ΩTtsI was obtained by three-parental hybridization and identified by PCR.Type III effector ex pression analysis showed that TtsI mutation could inhibit the transcription and expression of effector genes such as NopAA,NopD,NopL,and NopP in the presence of genistein.When TtsI mutated,it could significantly inhibit the synthesis of rhizobium HH103 type III effector.TtsI mutants and wild-type rhizobium HH103 were used to identify nodules in 10 soybean germplasm of different ecological regions.These results showed that the TtsI mutation could significantly reduce the average number of nodule and the dry weight of nodule.The nodule phenotype identification results of the introduced line population showed that the TtsI mutant significantly reduced the average nodule num ber of the introduced line.This showed that TtsI played an important role in the establishment of a soybean-rhizobia symbiotic system depending on other type III effectors.