Small RNA and degradome sequencing reveal the role of blackberry miRNAs in flavonoid and anthocyanin synthesis during fruit ripening

Blackberry shrubs are economically important for their production of small, pulped fruits. This species has attracted much attention because of the unique flavor of its fruits and their rich nutritional and medicinal value. In this study, microRNAs (miRNAs) and their target genes related to flavonoids and anthocyanins in blackberry fruits during ripening were analyzed and identified by small RNA and degradome sequencing technology, and the expression levels of key miRNAs in unripe and ripe blackberry fruits were verified via the RT-qPCR. A total of 258 known miRNAs were identified. Eighty differentially expressed miRNAs (DEMs) were detected in the fruits of the ripe group compared with those of the unripe group. Differentially expressed miR828-x/miR828-z and unigene0086056 (unknown function) were coexpressed. Moreover, miR858 had the most target genes for the synthesis of flavonoids and anthocyanins. Taken together, these results provide important value for improving the quality of blackberry fruits and breeding blackberry plants that produce high-flavonoid fruits for the pharmaceutical industry.