Transcriptomic and functional analyses unveil the role of long non-coding RNAs in anthocyanin biosynthesis during sea buckthorn fruit ripening

Fruit ripening is a developmental process regulated by a complex network of endogenous and exogenous cues. Sea buckthorn is an excellent material for fruit ripening studies due to its dramatic ripening process and high contents of nutritional and anti-oxidant compounds in berries. Here, the whole transcriptome of sea buckthorn fruit at three development stages were analysed using multiple high-throughput sequencings. We assembled and annotated 9,008 long non-coding RNAs (lncRNAs) in sea buckthorn fruits, and identified 118 differentially expressed lncRNAs (DE-lncRNAs) and 32 differentially expressed microRNAs in fruit developmental process. In addition, we predicted 1,061 cis-regulated and 782 trans-regulated targets of DE-lncRNAs, and these DE-lncRNAs are specifically enriched in the biosynthesis of ascorbic acid, carotenoids and flavonoids. Moreover, the silencing of two lncRNAs (LNC1 and LNC2) in vivo and expression analysis revealed that LNC1 and LNC2 can act as endogenous target mimics of miR156a and miR828a to reduce SPL9 and induce MYB114 expression, respectively, which lead to increased and decreased anthocyanin content as revealed by high-performance liquid chromatography analysis. Our results present the first global functional analysis of lncRNA in sea buckthorn and provide two essential regulators of anthocyanin biosynthesis, which provides new insights into the regulation of fruit quality.