The OfMYB1R114-OfSDIR1-like-OfCCD4 module regulates β-ionone synthesis in Osmanthus fragrans

Abstract

Osmanthus fragrans have a unique aroma, its extracts and its constituents have a wide range of biological activities, making them of great industrial value. β-ionone is a crucial factor in determining the aroma quality of O. fragrans. The synthesis mechanism of β-ionone is essential for studying the aromatic compounds in O. fragrans. This study demonstrated that the OfMYB1R114-OfSDIR1-like-OfCCD4 module regulates β-ionone synthesis in O. fragrans. A MYB-related transcription factor OfMYB1R114 increased β-ionone aroma substance and elevated OfCCD4 expression level through binding to the OfCCD4 promoter and activating its expression; this demonstrated a positive loop in β-ionone synthesis. Screening for interacting proteins using a cDNA library of O. fragrans petals, the interaction pair between OfMYB1R114 and OfSDIR1-like was validated. In addition, OfSDIR1-like negatively regulated β-ionone synthesis by ubiquitinating the OfMYB1R114 protein and decreasing the ability of OfMYB1R114 to activate its downstream target gene OfCCD4. Interestingly, OfMYB1R114 could directly bind to the OfSDIR1-like promoter and repress its transcription, revealing a negative feedback loop between OfMYB1R114 and OfSDIR1-like. Hence, this suggests that OfSDIR1-like is a new novel regulator that functions in β-ionone synthesis via the OfMYB1R114-mediated aroma pathway. The mechanistic framework revealed by the studies is that the OfMYB1R114-mediated module OfMYB1R114-OfSDIR1-like-OfCCD4 regulates β-ionone synthesis. It sheds light on the molecular mechanisms at the basis of aroma synthesis in O. fragrans and provides theoretical basis and technical guidance for the comprehensive utilisation and industrial development of O. fragrans aroma substance.