Fig. 4

Identification, male-specific expression, and phylogeny of partial RR duplicates. A The collinearity among the Y-SDRs of S. chaenomeloides and S. arbutifolia, and Z- and W-SDR of S. purpurea. From the inside to the outside: collinearity between the RR duplicates, information (position, number, direction) of the RR duplicates, and the start and end of the presented part of the SDRs are respectively displayed. In addition, the outermost regions of S. chaenomeloides and S. arbutifolia also show small RNA alignments along the partial RR duplicates and their surrounding 500-bp region in the male and female flower buds. B Phylogenetic relationship of the RR sequences (including intact genes (“C”) and partial duplicates (“S”: small duplicate; “L”: large duplicate)) identified in the Salicaceae species. The tree was rooted by the paralogous genes “RR16.” Abbreviations of all species: Ptrs: P. tremuloides; Ptra: P. tremula; Pal: P. alba; Ppr: P. pruinosa; Peu: P. euphratica; Ptr: P. trichocarpa; Pde: P. deltoides; Sch: S. chaenomeloides; Sar: S. arbutifolia; Spu: S. purpurea