Systematic identification of heat-responsive VQ genes and functional characterization of the TaVQ27-5A-TaWRKY51L-3A module in thermotolerance regulation in wheat (Triticum aestivum L.).

Valine-glutamine (VQ) proteins are plant-specific transcriptional cofactors that play crucial roles in plant growth, development, and stress responses. Heat stress (HS), one of the most detrimental abiotic stresses, severely impairs wheat growth, development, quality, and yield. Despite their importance in other plants, the role of VQ proteins in wheat's response to HS remains unexplored. In this study, we identified and systematically analyzed 37 heat-responsive VQ genes in wheat. Functional analyses in Arabidopsis (overexpression) and wheat (silencing) revealed that TaVQ27-5A positively regulates thermotolerance. Additionally, TaWRKY51L-3A was identified as an interacting protein of TaVQ27-5A through Y2H, BiFC, and LCA assays. Overexpression of TaWRKY51L-3A in Arabidopsis reduced thermotolerance, while silencing this gene in wheat enhanced thermotolerance. Y1H and dual-luciferase reporter gene assays showed that TaWRKY51L-3A directly activates the expression of TaNOX-3A, TaNOX-3B, and TaNOX-3D, while TaVQ27-5A represses this activation. In conclusion, this study provides the first evidence that a VQ protein regulates wheat heat stress responses through interaction with a WRKY transcription factor. These findings not only offer new insights into the functional mechanisms of VQ proteins but also present candidate genes for developing wheat varieties with enhanced thermotolerance.