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).