Chromosome-scale genome assembly provides insights into the molecular mechanisms of tissue development of Populus...

Populus wilsonii is an important species of section Leucoides, and the natural populations mainly grow in southwest China. In this study, a single genotype of wild P. wilsonii was sequenced and assembled at genome size of 477.35 Mb in 19 chromosomes with contig N50 of 16.3 Mb. A total of 38,054 genes were annotated, and 49.95% of the genome was annotated as repetitive elements. Phylogenetic analysis identified that the divergence between P. wilsonii and the ancestor of P. deltoides and P. trichocarpa was 12 (3-23) Mya. 4DTv and Ks distributions supported the occurrence of the salicoid WGD event (~65 Mya). The highly conserved collinearity supports the close evolutionary relationship among these species. Some key enzyme-encoding gene families related to the biosynthesis of lignin and flavonoids were expanded and highly expressed in the stems or leaves, which probably resist the damage of the natural environment. In addition, some key gene families related to cellulose biosynthesis were highly expressed in stems, accounting for the high cellulose content of P. wilsonii variety. Our findings provided deep insights into the genetic evolution of P. wilsonii and will contribute to further biological research and breeding as well as for other poplars in Salicaceae.