Identification of novel microRNAs for cold deacclimation in barley

Cold acclimation is crucial for the overwintering process of plants. Cold deacclimation is also important for plant survival in winter, which results in loss of freezing tolerance and initiation of growth. MicroRNAs (miRNAs) play crucial roles in regulating various physiological activities including cold response in plants. However, there is no study on miRNAs and their target genes in response to cold deacclimation in a cold-tolerant crop - barley (Hordeum vulgareL.). Here, we performed high-throughput sequencing of miRNAs of leaves during the cold deacclimation process using two barley cultivars with contrasting cold tolerance (Nure, tolerant and Tremois, sensitive). We found a total of 36 known and 267 novel miRNAs, including 12 known and 112 novel ones that are differentially expressed during cold deacclimation. The number of detected differentially expressed miRNAs was larger in Nure than that in Tremois, and the expression profile of miRNAs was dramatically different between Nure and Tremois. Moreover, we identified 13 known and 97 novel miRNAs, which have putative target genes during cold deacclimation. The putative targets of the novel miRNAs included genes encoding C-repeat binding factor (CBF) transcription factors, phytohormones, antioxidant, osmopretectant and flower development. Our results suggest that barley miRNAs respond quickly to cold deacclimation, and the larger number of miRNAs differentially expressed in the cold tolerantcv.Nure indicating that miRNAs might play an important role in the process of deacclimation. It sets a solid foundation for future studies and breeding programs on low temperature tolerance in barley.