马铃薯抗晚疫病基因Rpi-blb2的LRR区域多态性及分子进化分析

Nucleotide polymorphism and molecular evolution of the LRR region in potato late blight resistance gene Rpi-blb2

马铃薯抗晚疫病基因Rpi-blb2是来源于马铃薯野生种Solanum bulbocastanum中的一个具有广谱抗性的NBS-LRR类抗病基因。文章用PCR的方法从20个高抗晚疫病的马铃薯栽培种和20个高感晚疫病的马铃薯栽培种以及7个马铃薯野生种中克隆了Rpi-blb2基因的LRR区段。采用生物信息学方法对这些序列的相似性、多态性位点、核酸多样性指数等参数进行了分析,发现Rpi-blb2的LRR区域在核酸水平上变异程度很高,而且存在多处热点突变位点;通过对该区域的Ka/Ks值进行估算,发现Rpi-blb2的LRR区域总体上受到纯化选择,功能保守,但是LRR区域的不同部位所受到的选择压力却不尽相同。同时,从核酸水平来看,Rpi-blb2基因的LRR区域在马铃薯栽培种和马铃薯野生种之间没有发现明显的分化。

Rpi-blb2,which is originally derived from Solanum bulbocastanum,is a broad-spectrum potato late blight resistance gene and belongs to the NBS-LRR family.Here,the LRR homologues of Rpi-blb2 were cloned with PCR method from 40 potato cultivars（including 20 resistant potato cultivars and 20 susceptible ones） and 7 wild potato populations.Then,the similarities of the sequences,polymorphic（segregating） sites,and nucleotide diversities were estimated by bioinformatic methods.The results showed that high nucleotide polymorphism and some hot-spot mutations existed in the LRR region of Rpi-blb2.The test of Ka/Ks ratio showed that the function of LRR was conserved because of the purifying selection,although different positions of the Rpi-blb2 LRR region were under different selection pressures.Moreover,the LRR region of Rpi-blb2 had no clear differentiation between the cultivated and wild potatoes.