Deciphering microRNA-mRNA networks underlying flavonoids and anthocyanins syntheses in Hibiscus syriacus

Although flavonoids and anthocyanins are crucial pharmaceutical constituents in the petals of Hibiscus syriacus, the molecular mechanisms that underpin flavonoids and anthocyanins syntheses in H. syriacus remain largely unknown. In this study, the concentrations of flavonoids and anthocyanins were largely differed among the 16 H. syriacus cultivars. ‘Purple pillar’ (PP), ‘Qian si ban’ and ‘Red french cabaret’ cultivars had higher levels of flavonoids and anthocyanins. PP and ‘Large white’ (LW) were selected to further study flavonoids and anthocyanins syntheses. The concentrations of flavonoids and anthocyanins in PP were 150 % and 2764 % higher than those in LW. Consistently, the in vitro antioxidant activities of flavonoid extracts in PP were greater than those in LW. Integrated metabolomic and transcriptomic analyses revealed numerous differentially abundant metabolites and differentially expressed genes, which are mainly associated with biosynthesis of flavonoids and anthocyanins, and several differentially expressed transcription factors, such as MYBs, ethylene responsive factors (ERFs) and bHLHs, were identified in the petals of PP vs. LW. Additionally, microRNA (miRNA) profiling showed that several miRNAs were differentially expressed in the petals of PP vs. LW. The miRNA-mRNA networks that underlie flavonoids and anthocyanins syntheses were further dissected. For instance, Hs-MIR396d-p3 was upregulated and its target gene ERF-1 was downexpressed in the petals of PP vs. LW. Upregulation of Hs-miR858a_L-1R+ 1 that might target MYBR1 and MYB74 resulted in downexpression of MYBR1 and MYB74 in the petals of PP vs. LW. These results suggest that miRNA-mRNA networks play essential roles in regulating flavonoids and anthocyanins syntheses in H. syriacus.