GENOME AND POPULATION SEQUENCING OF ASPEN ADVANCES POPULUS AS A MODEL SYSTEM FOR PLANT RESEARCH

Aspens include European trembling (Populus tremula) and north American quaking (P. tremuloides) aspen, European white aspen (P. alba) and numerous Asian species. Aspens spread as clonal colonies that can persist for millennia, are keystone species supporting a wide diversity of species and produce a diverse array of secondary metabolites. Here, we present genome and population genetics characterisation of P. tremula and P. tremuloides. Our analyses show that while the aspen genome structure is similar to that of the P. trichocarpa reference genome, with highly conserved gene content, they are considerably more heterozygous. One notable exception is the sex-determination region, which has altered gene content compared to P. trichocarpa. We used population re-sequencing data to examine the relationship between gene characteristics, genomic context and evidence of selection, finding that 5 prime UTRs have high rates of positive and negative selection and confirming a negative relationship between gene co-expression connectivity and purifying selection. The aspen genomics resources presented here greatly improve the utility of Populus as a model system for functional and evolutionary genomics. Data collections and analysis tools related to this study are available at PopGenIE (popgenie.org).

白杨类群涵盖欧洲颤杨（Populus tremula）、北美颤杨（P. tremuloides）、欧洲银白杨（P. alba）以及众多亚洲白杨物种。白杨以克隆群落形式存续，可存活数千年，是支撑丰富物种多样性的关键物种，并能产生多样的次生代谢产物。本研究针对欧洲颤杨与北美颤杨开展基因组与群体遗传学特征解析。分析结果显示，尽管白杨的基因组结构与毛果杨（P. trichocarpa）参考基因组高度相似，基因含量也极为保守，但二者的杂合度显著更高。一个显著例外是性别决定区域，与毛果杨相比，该区域的基因含量发生了改变。本研究利用群体重测序数据，分析基因特征、基因组背景与选择信号之间的关联，结果发现5'非翻译区（5 prime UTRs）承受较高的正向选择与负向选择压力，并证实基因共表达连通性与纯化选择之间存在负相关关系。本研究提供的白杨基因组学资源，极大提升了杨属作为功能基因组学与进化基因组学模式系统的应用价值。本研究相关的数据集与分析工具可从PopGenIE（popgenie.org）获取。