Negative regulatory role of LiSRM1 in monoterpene biosynthesis in Lilium ‘Siberia’

Lilium 'Siberia' is a commercially significant cut flower worldwide with an elegant shape and appealing scent, originating from the release of monoterpenes. However, the regulatory mechanism underlying lily monoterpenes has been largely unexplored. Here, a MYB transcription factor from 'Siberia' petals, LiSRM1, whose expression was negatively associated with monoterpene release. Subcellular localization analysis indicated that LiSRM1 was localized to the nucleus. A virus-induced gene silencing (VIGS) assay showed that silencing of LiSRM1 not only significantly increased the synthesis of linalool and ocimene, but also elevated the expression of LiLiS and LiOcS, respectively. Transient overexpression of LiSRM1 exerted opposite effects. Furthermore, yeast one-hybrid assays (Y1H) and dual-luciferase assays (LUC) demonstrated that LiSRM1 directly bound the promoters of LiLiS and LiOcS, respectively, and repressed their expression. Taken together, the results suggested that LiSRM1 negatively regulated monoterpene release and mediated the expression of LiLiS and LiOcS in Lilium.