Identification of Candidate miRNAs and their Targets Involved in the Dormancy Regulation of Grapevine.

Bud dormancy in grapevines plays an important role for survival under harsh conditions. microRNAs (miRNAs) are small non-coding RNAs molecules (typically 21 or 22 nt) that affect many biological processes by negatively regulating gene expression primarily at the post-transcriptional level. To identify and evaluate the roles of miRNAs in bud dormancy in grapevine, we identified conserved and novel miRNAs using high-throughput sequencing and subsequent bioinformatics analyses. We analyzed small RNA libraries from bud tissue at endodormancy (short photoperiod, SD) or paradormancy (long photoperiod (LD) stages.  Results revealed conserved and potentially novel miRNAs, a number of which were differentially expressed between these two dormancy stages. Potential target genes were predicted using an in-house Perl script. We compared RNA-Seq derived transcriptomes of LD and SD bud or shoot tip tissues and identified several differentially expressed genes that could be involved in the dormancy cycle. Inverse expression between miRNAs and the corresponding target genes in paradormancy vs. endodormancy stages indicated potential post-transcriptional regulation of some of these genes by miRNAs. This study has identified several conserved and novel miRNAs with a potential role in the bud dormancy cycle.