大黄属(蓼科) 植物ｎｄｈＦ 基因的适应性进化

大黄属(Rheum L.)是蓼科(Polygonaceae)中一个高度分化的大属，广泛分布在亚洲和欧洲的高山和沙漠地区，全世界约60种，其中在青藏高原及其邻近地区发现了约40种。该属种的高度分化曾被推测是第三纪末青藏高原的快速隆升以及第四纪气候的反复变化所引发的适应性辐射导致。为进一步了解大黄属植物辐射式物种分化的分子适应机制，该研究选取34个形态上多样化的大黄属物种，利用系统发育分析软件，在时间框架下采用位点模型和分支模型对大黄属的叶绿体ndhF基因进行了适应性进化分析。结果表明：大黄属植物的分子进化系统树呈现短而平行的辐射式分支式样，显示出典型的物种快速辐射多样化特征；用位点模型检验ndhF基因是否存在经受正向选择(ω>1)时，在氨基酸水平上共鉴定出3个NDHF亚基的正选择位点(188H，465H，551L)，对NDHF亚基的二级结构进行分析后发现编码的188H氨基酸位于α螺旋上。大黄属植物可能通过这些结构域的适应性进化，适应青藏高原的快速隆升以及第四纪气候的反复变化而引发的陆地生态系统改变。该研究结果可为今后对该属植物的实验分析提供首选位点。

Adaptive evolution of the ndhF gene in the genus Rheum(Polygonaceae)

Rheum, a highly diversified genus of Polygonaceae, comprising about 60 species, is mainly distributed in the mountainous and desert regions in Asia and Europe. Its high diversification in the Qinghai-Tibetan Plateau and adjacent areas,where approximately 40 species have been described,was suggested to result from the adaptive radiation triggered by the recent uplifts of the Qinghai-Tibetan Plateau and the quaternary climate oscillations. To further understand the molecular adaptation linked to Rheum radiation, the adaptive evolution of chloroplast ndhF gene belonging to 34 morpho-logically diversified species of the genus Rheum were tested by using the Phylogenetic Analysis Program in this study. The results showed that the pattern of phylogenic tree was a typical “paralleling” phylogeny, suggesting a radiative di-versification. Three amino acid sites (188H,465H,551L) of NDHF subunit were identified under positive selection (ω>1) ,and the secondary structures of NDHF subunit showed that the 188th amino acid was located in the α-helix. The changes of these adaptive sites may be associated with the evolution of NDH to adapt the extreme habitats of Rheum spe-cies caused by the extensive uplifts of the QTP and the quaternary climate oscillations.