苹果属S-RNase基因的进化研究

Evolutionary Studies of S-RNase Genes in Genus Malus

【目的】通过分析苹果属植物自交不亲合性位点S-RNase基因的序列,研究S-RNase基因在苹果属的进化历史,序列分歧特点和遗传多态性。【方法】利用栽培苹果的S-RNase基因序列在GenBank数据库中检索和鉴定所有已知的苹果属植物的S-RNase基因,同时利用S-RNase基因的保守引物获得陇东海棠和变叶海棠的S-RNase基因序列。通过系统发育分析研究S-RNase基因的进化历史,进而计算dN/dS比值揭示S-RNase基因序列分歧的特点,最后估计并比较苹果属不同类群S-RNase基因的遗传多态性及其遗传分化。【结果】苹果属植物的S-RNase基因可以分为16个亚类,同一亚类S-RNase基因的序列分歧较小,亚类之间的分歧很大。S-RNase基因的成对dN/dS比值中有50%的大于1,并且滑动窗分析显示S-RNase基因具有多个dN/dS比值显著大于1的区域。栽培苹果和野生苹果在S-RNase基因的遗传多态性上没有明显差异。在所涉及的苹果属野生类群中,栽培苹果与塞威士苹果在S-RNase基因上的遗传分化最小。【结论】适应性氨基酸替换在苹果属植物S-RNase基因的序列分歧上发挥了重要作用。现有的S-RNase基因数据显示栽培驯化没有导致栽培苹果S-RNase基因遗传多态性的降低,基于S-RNase基因的遗传分化支持栽培苹果是由塞威士苹果驯化而来的观点。

[Objective] By analyzing the sequences of S-RNase gene at the self-incompatibility loci, its evolutionary history, sequence divergence and genetic polymorphism were studied for species belonged to genus Malus. [ Method ] All of the Malus S-RNase genes were retrieved from GenBank by NCBI BLAST using the known S-RNase genes of Malus domestica, except four S-RNase genes of M. kansuensis and M. toringoides which were obtained by PCR amplification and clone sequencing. The evolutionary history of the Malus S-RNase genes was studied by phylogenetic analysis, and the characteristics of sequence divergence were analyzed. The genetic polymorphisms and divergence were estimated for different taxa of Malus. [Result] The S-RNase genes of Malus can be divided into 16 clearly delimitated subgroups, the divergence of S-RNase genes within subgroups was low, while it was high among subgroups. There were 50% dN/dS estimations that were greater than 1 among S-RNase gene pairs, and S-RNase genes possessed multiple codons of which dN/dS ratio was greater than 1. There was no difference in the genetic polymorphism between M. domestica and wild Malus species, and the closet taxa with M. domestica was M. sieversii based on divergence of S-RNase gene. [Conclusion] Adaptive amino acid substitutions play an important role in the sequence divergence of S-RNase in Malus. According to the analysis of S-RNase genes belonging to Malus, it was found that the genetic polymorphism of M. domestica has not been affected by cultivation, and M. domestica was derived from M. sieversii through human domestication.