Detecting the Candidate Gender Determinants by Bioinformatic Prediction of miRNAs and Their Targets from Transcriptome Sequences of the Male and Female Flowers in Salix suchowensis

MicroRNAs (miRNAs) belong to a class of small, noncoding, and endogenous single-stranded RNAs that negatively regulate gene expression at the posttranscriptional level. Potential miRNAs can be identified based on sequence homology since miRNAs are highly conserved in plants. In this study, we aligned the expressed sequence tags derived from flower buds of male and female S. suchowensis to miRNAs in the miRBase, which enable us to identify 34 potential miRNAs from flower buds of the alternate sexes. Among them, 11 were from the female and 23 were from the male. Analyzing sequence complementarity led to identification of 124 and 55 miRNA targets in the male and female flower buds, respectively. By mapping the target genes of the predicted miRNAs to the sequence assemblies of S. suchowensis, a miR156 mediated gene was detected at the gender locus of willow, which was a transcription factor involved in flower development. It is noteworthy that this target is not expressed in male flower, while it is expressed fairly highly in female flower based on the transcriptome data derived from the alternate sexes of willows. This study provides new bioinformatic clue for further exploring the genetic mechanism underlying gender determination in willows.