Genome-wide analysis of miRNAs in Carya cathayensis

Background: MicroRNA (miRNA) plays an important role in plant development regulation. Hickory is an economically important plant in which the amount of flowering determines its production. Results: Here, 51 conserved miRNAs, which belong to 16 families and 195 novel miRNAs were identified in hickory genome. For each conserved miRNA family, we used sequences from hickory and other plants to construct a phylogenetic tree, which shows that each family has members in hickory. Some of the conserved miRNA families (i.e., miR167 and miR397) have more members in hickory than in other plants because of gene expansion. MiR166 exhibited tandem duplication with three copies being observed. Many members of these conserved miRNA families were detected in hickory flowers, and the expression patterns of target genes were opposite to those of the related miRNAs, indicating that miRNAs may have important functions in floral regulation of hickory. Conclusions: Taken together, a comprehensive analysis was conducted to identify miRNAs produced in hickory flower organs, demonstrating functional conservation and diversity of miRNA families among hickory, Arabidopsis, grape, and poplar.