MicroRNAs (miRNAs) are a class of short non-coding RNAs found widely in eukaryotic organisms. The ptc-MIR169 gene family, which consists of 33 members, is the largest miRNA gene family in poplar (Populus trichocarpa) It is significant to analyze the evolution of the ptc-MIR169 gene family in order to understand the evolutionary mechanisms of miRNAs in poplar. In the present study, we investigated the molecular phylogeny, duplication, expression and target genes of the MIR169 gene family in poplar. Both tandem duplications and chromosome segmental duplications contributed to the expanding of pt...