High temperature (HT) is one of the most important environmental stress factors and seriously threatens plant growth, development, and production. VQ motif-containing proteins are transcriptional regulators that have been reported to regulate plant growth and developmental processes, including responses to biotic and abiotic stresses. However, the relationships between VQ motif-containing proteins and HT stress have not been studied in depth in plants. In this study, transgenic apple (Malus domestica) plants overexpressing the apple VQ motif-containing protein-coding gene (MdVQ37) were exposed to HT stress, and the transgenic lines exhibited a heat-sensitive phenotype. In addition, physiological and biochemical studies revealed that, compared with WT plants, transgenic lines had lower enzymatic activity and photosynthetic capacity and lower amounts of nonenzymatic antioxidant system metabolites under HT stress. Transcriptome analysis revealed 1379 genes whose expression differed between the transgenic lines and WT plants. GO and KEGG pathway analyses showed that transcription factor activity and plant hormone signaling pathways were differentially influenced and enriched in the transgenic lines. Salicylic acid (SA) content analysis indicated that overexpression of MdVQ37 reduced the content of endogenous SA by regulating the expression of SA catabolism-related genes, which ultimately resulted in disruption of the SA-dependent signaling pathway under HT stress. The application of SA slightly increased the survival rate of the transgenic lines under HT stress. Taken together, our results indicate that apple MdVQ37 has a regulatory function in basal thermotolerance by modulating the activity of transcription factors and SA homeostasis. Overall, this study provides novel insights that improve our understanding of the various functions of VQ motif-containing proteins.

中文翻译：

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MdVQ37过表达通过影响转录因子活性和水杨酸稳态降低转基因苹果的基础耐热性

高温(HT)是最重要的环境胁迫因素之一，严重威胁植物的生长、发育和生产。含有 VQ 基序的蛋白质是转录调节因子，据报道可调节植物生长和发育过程，包括对生物和非生物胁迫的反应。然而，尚未在植物中深入研究含有 VQ 基序的蛋白质与 HT 胁迫之间的关系。在本研究中，转基因苹果 (海棠) 植物过表达含有苹果 VQ 基序的蛋白质编码基因 (MdVQ37) 暴露于 HT 胁迫下，转基因品系表现出热敏感表型。此外，生理生化研究表明，与WT植物相比，转基因株系在HT胁迫下具有较低的酶活性和光合能力以及较低的非酶抗氧化系统代谢产物。转录组分析揭示了 1379 个基因，其在转基因株系和 WT 植物之间的表达不同。GO和KEGG通路分析表明，转录因子活性和植物激素信号通路在转基因株系中受到不同程度的影响和富集。水杨酸（SA）含量分析表明，MdVQ37通过调节SA分解代谢相关基因的表达来降低内源性SA的含量，最终导致HT胁迫下SA依赖性信号通路的破坏。SA的应用略微提高了转基因株系在HT胁迫下的存活率。总之，我们的结果表明苹果 MdVQ37 通过调节转录因子的活性和 SA 稳态而在基础耐热性中具有调节功能。总体而言，这项研究提供了新的见解，提高了我们对含 VQ 基序的蛋白质的各种功能的理解。