# Ethylene-Mediated VvERF003 Promotes Flavonol Accumulation by Upregulating VvFLS1 and VvCHI1 in ‘Chardonnay’ Grape Berry Skin

## TL;DR

This study shows how ethylene increases flavonol levels in grape berries by activating a specific gene, VvERF003, which in turn boosts the expression of flavonol biosynthesis genes.

## Contribution

The study identifies VvERF003 as a novel ethylene-responsive transcription factor that promotes flavonol accumulation in grape berries.

## Key findings

- Ethylene treatment increased flavonol content in grape berry skin, while 1-MCP reduced it.
- VvERF003 directly activates the promoters of VvCHI1 and VvFLS1 to enhance flavonol biosynthesis.
- Overexpression of VvERF003 in grape tissues led to higher flavonol accumulation.

## Abstract

Flavonols are an important secondary metabolite in grape, which play a crucial role in plant growth and development, human health, and wine making. Ethylene and its inhibitor 1-Methylcyclopropene (1-MCP) are widely used in grape berry production. However, the regulation mechanism of flavonol biosynthesis by ethylene and 1-MCP remains elusive in yellow-green grape varieties. Here, the content of flavonols in ‘Chardonnay’ grape berry skin after ethylene treatment was significantly higher than the control, while 1-MCP treatment was lower than the control. The phenylpropanoid biosynthesis-related genes and a transcription factor VvERF003 were screened for possible involvement in ethylene-mediated flavonol biosynthesis by transcriptome sequencing. The role of VvERF003 was further proved to promote flavonol accumulation in the transient overexpression of grape fruits and leaves, and the upregulation of genes related to flavonol biosynthesis. Furthermore, VvERF003 promoted flavonol biosynthesis by directly binding to and activating the promoters of VvCHI1 and VvFLS1, and positively regulated their expression. These results indicated that VvERF003 was induced by ethylene and promoted the accumulation of flavonols in ‘Chardonnay’ grape berry skin by positively regulating the flavonol biosynthesis genes VvCHI1 and VvFLS1.