Using next-generation deep sequencing, they identified a total of 206 miRNAs, comprising 115 known and 84 novel miRNAs, and seven potential miRNA candidates. Of these miRNAs, 98 (57 known and 41 novel miRNAs) were differentially expressed under heat stress. A total of 101 miRNA-target pairs consisting of 44 miRNAs and 71 target genes were verified by degradome sequencing. Target annotation suggested that these miRNAs might be important in the regulation of specific stress-responsive genes, including many transcription factors and a series of genes encoding important enzymes of functional proteins targeted by miRNAs.
Further functional analysis suggested these target genes were related to protein synthesis, transport and turnover, cell wall organization, protein folding, antioxidation, defense response, and modulation of attenuated plant growth and development under heat stress. The expression patterns of 15 randomly selected miRNAs derived from quantitative reverse transcription PCR had similar trends as those derived from high-throughput sequencing, as well as the expression patterns of six target genes under heat stress.
These results improve our understanding of the miRNA-mediated regulatory network of heat stress response in B. luminifera, which will contribute to improving heat stress-resistant breeding in woody plants.