VvMYB44–VvERF045 complex is involved in abscisic acid-induced sugar accumulation by activating <i>VvSPS4</i> expression in grapes

Phytohormones play a crucial role in regulating fruit ripening and quality, particularly in soluble sugar accumulation. Despite this, the molecular mechanisms behind hormone-induced sugar accumulation in grapes are not well understood. Our study shows that abscisic acid (ABA) enhances grape berry ripening and soluble sugar levels. We generated a transcriptome dataset from grape berries subjected to hormone treatment and constructed a potential regulatory network related to sugar accumulation using weighted gene co-expression network analysis (WGCNA). Furthermore, we identified five structural genes (SGs) and 44 transcription factors (TFs) responsive to ABA that potentially regulate sugar accumulation in grape berries. Notably, VvMYB44 was emphasized due to its highest expression in ABA-treated mature fruits among these TFs. It binds to the promoter of <i>VvSPS4</i> and activates its expression, thereby influencing sucrose metabolism. Additionally, VvERF045 interacts with VvMYB44, further amplifying its transcriptional activation of <i>VvSPS4</i>. Overexpressing <i>VvERF045</i> also increased the soluble sugar levels in tomato fruits. These findings underscore the role of the VvMYB44-VvERF045 complex in sugar accumulation and provide new insights into the molecular mechanisms underlying sugar accumulation in grapes.