Integrative analysis of miRNA profile and degradome reveals post-transcription regulation involved in fragrance formation of Rosa rugosa.

Rosa rugosa is renowned for its fragrant essential oils (EOs) including the primary volatile compounds such as terpenes (geraniol and citronellol) and 2-phenylethanol. While the role of miRNAs in plant secondary metabolism has been explored, their involvement in EOs metabolism remains largely unknown. Sequencing of the petals of R. rugosa identified 383 conserved miRNAs and 625 novel miRNAs including 53 miRNAs differentially expressed in a strong fragrance variety R. rugosa 'White Purple Branch'. Degradome sequencing predicted 1969 targets enriched in GO terms involved in the negative regulation of macromolecule metabolic process. Furthermore, 122 targets of differentially expressed miRNAs were enriched in phenylalanine metabolism and other KEGG pathways. A post-transcriptional regulation network of 52 miRNAs and 70 miRNA-transcription factor modules target terpene and 2-phenylethanol biosynthesis pathways. Six interactions including miR535f-RrHMGR, NOV146-RrNUDX1, miR166l-RrHY5 and miR156c-RrSPL2 were validated using RNA ligase-mediated RACE. Sequence alignment revealed that the NOV146-RrNUDX1 was conserved in the Rosa genus. Moreover, weaker silencing of RrNUDX1 by NOV146 contributed to the stronger fragrance of R. rugosa. These findings offer a comprehensive understanding of the post-transcriptional regulation involved in essential oil biosynthesis and identify candidate miRNAs for further genetic improvement of EO yields in R. rugosa.