响叶杨（杨属）叶绿体基因组测序与比较分析
Complete sequence and comparative analysis of the chloroplast genome of the Chinese aspen (Populus adenopoda, Salicaceae)

杨属植物是一类具有重要经济、生态和科学研究价值的林木资源，然而目前关于整个杨属物种之间叶绿体基因组结构变异的信息却知之甚少。本研究中，我们对响叶杨的叶绿体基因组进行测序和组装，并将其与杨属其他11个叶绿体基因组进行比较分析。结果表明，响叶杨叶绿体基因组全长158,591 bp，其中两个反向重复序列区（IR）长度均为27,667 bp，长单拷贝序列区（LSC）和短单拷贝序列区（SSC）长度分别为84,634和18,623 bp。通过对杨属12个物种的叶绿体基因组进行比较，只发现了6个相对较大的插入缺失，因此整体而言，杨属的叶绿体基因组结构是高度保守的。系统发育分析结果显示，杨属中12个物种组成了3个具有高支持率的进化支，响叶杨与其他白杨组物种聚为一支，并且与银白杨的亲缘关系最近。本研究基于叶绿体基因组数据揭示了杨属的进化历史，将有助于进一步开展杨属植物基于叶绿体DNA序列数据的群体遗传学及其他分子生态学研究。
Although Populus (Saliaceae) is an important group of forest trees in the sense of economy, ecology and scientific researches, few is known about the structural and sequence variation of chloroplast genome across the genus. We sequenced and characterized the complete chloroplast genome of the Chinese aspen (Populus adenopoda), and made comparative analyses of the structure variation of the chloroplast genomes of P. adenopoda and other 11 poplars. The P. adenopoda chloroplast genome is 158,591bp in length, exhibits a typical quadripartite structural organization, consisting of a LSC region of 84,634 bp, two IR regions of 27,667 bp and a SSC region of 18,623 bp. Comparison of the cp genome structure and gene order to those of the 12 Populus species indicated that the chloroplast genomes of this genus are rather conservative, only six large deletions or insertions were found across the whole genome. Phylogenetic analysis demonstrated that the 12 Populus species clustered into three well-supported clades, and Chinese aspen is most closely related to the white poplar, P. alba. Our work will better our understating of the evolutionary history of Populus, and will be useful to future population genetics and other molecular ecology studies of poplars based on chloroplast DNA sequences