Zhao Liang, Jiang Xi-Wang, Zuo Yun-Juan, Liu Xiao-Lin, Chin Siew-Wai, Haberle Rosemarie, Potter Daniel, Chang Zhao-Yang, Wen Jun
College of Life Sciences, Northwest A&F University, Yangling, Shaanxi, 712100, China.
College of Life Sciences, Jianghan University, Wuhan, Hubei, 430056, China.
PLoS One. 2016 Jun 13;11(6):e0157123. doi: 10.1371/journal.pone.0157123. eCollection 2016.
Prunus is an economically important genus well-known for cherries, plums, almonds, and peaches. The genus can be divided into three major groups based on inflorescence structure and ploidy levels: (1) the diploid solitary-flower group (subg. Prunus, Amygdalus and Emplectocladus); (2) the diploid corymbose group (subg. Cerasus); and (3) the polyploid racemose group (subg. Padus, subg. Laurocerasus, and the Maddenia group). The plastid phylogeny suggests three major clades within Prunus: Prunus-Amygdalus-Emplectocladus, Cerasus, and Laurocerasus-Padus-Maddenia, while nuclear ITS trees resolve Laurocerasus-Padus-Maddenia as a paraphyletic group. In this study, we employed sequences of the nuclear loci At103, ITS and s6pdh to explore the origins and evolution of the racemose group. Two copies of the At103 gene were identified in Prunus. One copy is found in Prunus species with solitary and corymbose inflorescences as well as those with racemose inflorescences, while the second copy (II) is present only in taxa with racemose inflorescences. The copy I sequences suggest that all racemose species form a paraphyletic group composed of four clades, each of which is definable by morphology and geography. The tree from the combined At103 and ITS sequences and the tree based on the single gene s6pdh had similar general topologies to the tree based on the copy I sequences of At103, with the combined At103-ITS tree showing stronger support in most clades. The nuclear At103, ITS and s6pdh data in conjunction with the plastid data are consistent with the hypothesis that multiple independent allopolyploidy events contributed to the origins of the racemose group. A widespread species or lineage may have served as the maternal parent for multiple hybridizations involving several paternal lineages. This hypothesis of the complex evolutionary history of the racemose group in Prunus reflects a major step forward in our understanding of diversification of the genus and has important implications for the interpretation of its phylogeny, evolution, and classification.
李属是一个具有重要经济意义的属，以樱桃、李子、杏仁和桃子而闻名。根据花序结构和倍性水平，该属可分为三大类：(1) 二倍体单花组（李亚属、扁桃亚属和扁核木亚属）；(2) 二倍体伞房花序组（樱亚属）；(3) 多倍体总状花序组（稠李亚属、月桂樱亚属和马登李属）。质体系统发育表明李属内有三个主要分支：李-扁桃-扁核木分支、樱分支和月桂樱-稠李-马登李分支，而核糖体DNA内转录间隔区（ITS）树将月桂樱-稠李-马登李解析为一个并系群。在本研究中，我们利用核基因座At103、ITS和6-磷酸葡萄糖脱氢酶（s6pdh）的序列来探索总状花序组的起源和演化。在李属中鉴定出两个At103基因拷贝。一个拷贝存在于具有单花和伞房花序的李属物种以及具有总状花序的物种中，而第二个拷贝（II）仅存在于具有总状花序的分类群中。拷贝I序列表明，所有总状花序物种形成一个由四个分支组成的并系群，每个分支都可通过形态学和地理学来定义。结合At103和ITS序列构建的树以及基于单基因s6pdh构建的树，其总体拓扑结构与基于At103拷贝I序列构建的树相似，At103-ITS联合树在大多数分支中显示出更强的支持度。核基因At103、ITS和s6pdh数据与质体数据一致，支持多倍体化事件促成了总状花序组起源的假设。一个分布广泛的物种或谱系可能作为多个杂交事件的母本，涉及多个父本谱系。李属总状花序组复杂进化历史的这一假设反映了我们对该属多样化理解的重大进步，对其系统发育、演化和分类的解释具有重要意义。
