CmVNI2-CmMYB3 module regulates flavonol biosynthesis in response to low temperature in chrysanthemum flower

Flavonols represent a large subgroup of flavonoids and function as the principal bioactive compounds in tea and medicinal chrysanthemum (Chrysanthemum morifolium) flowers. Low temperature is one of the most significant environmental factors influencing flavonol accumulation. Nevertheless, the regulatory mechanisms governing flavonol biosynthesis in response to low temperature remain predominantly uncharacterized. In this study, we observed decreased flavonol accumulation in chrysanthemum flowers under low-temperature conditions, correlating with reduced expression of the NAC transcription factor VND-INTERACTING2 (VNI2). The suppression of CmVNI2 resulted in diminished flavonol content. DNA affinity purification sequencing and RNA sequencing analyses demonstrated that CmVNI2 directly regulates the expression of CmF3H and CmMYB3, two genes essential for flavonol biosynthesis. In addition, transient overexpression of CmMYB3 in CmVNI2 RNA interference plants restored flavonol accumulation. The study establishes that the CmVNI2-CmMYB3 module plays a crucial role in regulating flavonol biosynthesis in chrysanthemum flowers under low-temperature stress and identifies potential target genes for enhancing the bioactive properties of chrysanthemum as a tea or medicinal herb.