樟科楠属植物系统发育基因组学研究

Besides of producing high-quality wood and selecting in forestation, a number of plants in the genus Phoebe are source of valuable secondary metabolites such as alkaloids, terperoids, and flavonoids. Some of these chemical constituents showed various activities such as antitumor, antiplasmodial, antimicrobial etc. Phoebe is large (c. 100 sp.) genus of trees and forms a distinct, monophyletic clade in the family Lauraceae. At the species level, however, the reported nuclear ITS and LEAFY intron II sequences failed to resolve the phylogenetic and species identification problems in this genus. The genus Phoebe includes over 30 species distributed in South China, with 12 species in Yunnan and 8 species in Guangxi, which indicated that the area including Yunnan, Guangxi, and neighboring countries of Southeast Asia could be important for the dispersion and speciation of Phoebe species in Asia. The aim of this research is to resolve the major phylogenetic relationships of 30 Phoebe species of tropic East Asia through large chloroplast genome sequence data and restriction- site-associated genome sequencing data. All of these target species could collect in a special garden for protection and research. Combining with the morphological data and geographical data, this study could further deduce the details of dispersion and speciation of Phoebe species in Asia. The results with clear phylogenetic relationships and explicit sources will provide an effective way to enhance the management and utilization of Phoebe plant.

樟科楠属植物含阿朴啡类生物碱，多为香料、建筑和油脂化工的重要原料，是理想的绿化造林树种。楠属植物有近百种，其单系属性得到分子系统学支持，但种间关系不清，形态鉴别困难，条形码片段分辨率低，尚缺分子系统学证据支持的分类系统。前期普查结果显示此类群在中国有30种，云南和广西的物种数最多。前期调查发现仅云南就分布有12种，预示滇桂两省及邻近东南亚地区可能是楠属植物重要的扩散和分化区域。为构建支持率较高的系统发育框架，探究楠属植物在热带东亚的分化过程，并建成遗传背景清晰的专类种质资源圃，本项目拟从南部各省及东南亚地区引种收集楠属物种30种，建成专类种植资源圃。利用二代测序技术完成收集种类的叶绿体基因组和简化基因组测序，构建高分辨率的进化树，并综合形态性状进行系统性分析。以期厘清楠属各种之间的亲缘关系，评价各个树种具经济价值的性状，便于对种质资源的开发和利用。

热带及亚热带地区的樟科物种关系不清，形态鉴别困难，但作为优质用材树种和潜力药用化合物的代谢植物又十分重要，然而多数种类已十分罕见。本项目选取亚洲重要的楠属资源植物为研究对象，重点关注中国及东南亚周边地区的楠属树种，以期厘清这些楠属物种之间的进化关系。通过对收集到的36种楠属树种，特别是30种已育苗的楠属植物，和已有的鳄梨亚族（Subtrib. Perseineae Kosterm.）物种进行系统发育关系重建发现：鳄梨亚族可分为赛楠-莲桂分支（Dehaasia-Nothaphoebe clade），北油丹分支（Alseodaphnopsis clade），鳄梨分支（Persea clade），楠分支（Phoebe clade）和润楠分支（Machilus clade）。此六分支拓扑结构证实楠属植物是单系类群。进一步的简化基因组（RAD）核苷酸变异位点（SNP）构建的系统发育关系支持楠属植物分为两组：以大果楠、景东楠、红梗楠和普文楠为代表的大果组，以披针叶楠、桢楠、紫楠和白楠为代表的小果组。而质体基因组构建的系统发育关系支持大果组进一步分为两亚组，一亚组包含大果楠和景东楠等，另一亚组包含红梗楠和普文楠等；小果组也进一步分为两亚组，一亚组包含披针叶楠和白楠等；另一亚组包含桢楠和紫楠等。部分物种通过两种分析发现明显的核质冲突，预示楠属植物内部的组间和组内物种间可能在历史上发生过古老杂交事件，或者至今仍存在谱系分化不完全的现象。综合形态性状进行系统性分析发现，楠属植物叶片干重、叶片周长、叶面积和叶脉数目存在显著的系统发育信号。以上工作明确了楠属植物的系统发育框架，并找到了系统发育相关的性状，为我们下一步开展群体和进化研究指明了方向。