Small RNA analysis of epidermis uncovered miRNAs involved in cuticle biosynthesis in Brassica napus

To investigate the function of small RNAs in cuticle biosynthesis in B. napus, we constructed four small RNA libraries from stem epidermis of wax-deficient and wild-type materials for sequencing. Subsequently, a total of 43,840,451 clean reads were generated and 24nt sequences represented the dominant percentage. Totally, 300 unique conserved miRNAs were identified and 8 of them showed differentially expressed. In addition, the expression of six novel miRNAs were also changed. After target prediction and function annotation, three miRNAs (aly-miR165a-5p, aly-miR408-5p, and novel-mir2) might influence cuticle morphogenesis not only by repressing the biosynthesis of cuticular substrates and components, but also blocking the transmembrane transport processes. The expression level of aly-miR408-5p and aly-miR165a-5p were increased in glossy materials examined by stem-loop qRT-PCR, while their predicted target genes (BnaC04g29170D, BnaA01g25630D, BnaA06g40560D) were down-regulated. These results suggested that miRNAs might influence cuticle biosynthesis by repressing cuticle-related genes expression in B. napus. Both the biosynthesis and secretion processes of cuticlular components might be influenced by miRNAs. These results will promote the study of post-transcriptional regulation mechanisms of cuticle biosynthesis in B. napus and provide new direction for further research. Four small RNA libraries were constructed for glossy mutant and wildtype materials of rapeseed.