Identification of anthocyanin-related microRNAs in ornamental kale (Brassica oleracea L. var. acephala) by high throughput sequencing

Anthocyanins have been found to be responsible for the pigmentation of red, purple and blue colors in plants. MicroRNA (miRNA) plays an important role in the regulation of anthocyanin biosynthesis in plants. However, few miRNAs and their corresponding functions related to anthocyanin biosynthesis in ornamental kale (Brassica oleracea var. acephala) have been reported. In this study, small RNA (sRNA) and degradome libraries from inner and outer leaves (IL and OL) of ornamental kale line “Pigeon Red” were constructed, respectively. Totally, 139 known and 14 novel miRNAs were identified by sRNA sequencing, and 304 target genes cleaved by 92 bo-miRNAs were identified by degradome sequencing. Of these, 5 miRNAs and their corresponding targets were potentially involved in the anthocyanin biosynthesis. And 35 miRNAs were differently expressed between IL and OL. Integrated analysis of sRNA-Seq, degradome sequencing and RNA-Seq revealed that bo-miR828 and its targets potentially play a key role in the regulation of anthocyanin biosynthesis in ornamental kale leaves. Finally, an inverse correlation between the expression of bo-miR828 and its targets was revealed by both qRT-PCR and high-throughput sequencing. These results represented a comprehensive expression profiling of miRNAs related to anthocyanin accumulation in B.oleracea var. acephala and provided important clues for understanding the regulatory network of anthocyanin biosynthesis mediated by miRNA in Brassica crops.