High temperature reduces anthocyanin accumulation in various horticultural plants. However, the molecular mechanisms underlying the high-temperature-induced reduction of anthocyanin in grape (Vitis vinifera) remain poorly understood. In this study, VvMYB44-1 was identified as a transcriptional repressor of anthocyanin biosynthesis in grape berries, and its gene expression was strongly induced by high-temperature treatment. Overexpression of VvMYB44-1 inhibited anthocyanin accumulation in both grape berries and tobacco (Nicotiana tabacum) by repressing the transcription of the anthocyanin biosynthesis genes dihydroflavonol-4-reductase (VvDFR) and UDP-glucose flavonoid-3-O glucosyltransferase (VvUFGT).. Furthermore, the interaction between VvMYB44-1 and VvWDR2 competitively inhibited the formation of the MYB-bHLH-WD40 (MBW) activation complex and weakened the transcriptional activity of the complex, thereby decreasing anthocyanin accumulation. Additionally, VvMYB44-1 facilitated cytokinin accumulation by up-regulating the expression of the cytokinin synthesis gene lonely guy 8 (VvLOG8) and inhibiting the cytokinin degradation gene cytokinin oxidase 4(VvCKX4), thus contributing to cytokinin-mediated anthocyanin inhibition in grape berries. Moreover, the inhibitory effect of VvMYB44-1 on anthocyanin biosynthesis and its downstream target genes was weakened with the deletion of the ethylene-responsive element binding factor-associated amphiphilic repression (EAR) motif, indicating that the EAR motif is indispensable for the inhibitory effect of VvMYB44-1 on anthocyanin biosynthesis in grapes. These results provide insights into the regulatory network of VvMYB44-1 in high-temperature-mediated anthocyanin biosynthesis in grapes.

中文翻译：

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转录因子 VvMYB44-1 在高温下减少葡萄花青素的生物合成中发挥作用


高温减少了各种园艺植物中花青素的积累。然而，高温诱导葡萄 （Vitis vinifera） 中花青素还原的分子机制仍然知之甚少。本研究鉴定 VvMYB44-1 是葡萄浆果花青素生物合成的转录抑制因子，高温处理强烈诱导其基因表达。VvMYB44-1 的过表达通过抑制花青素生物合成基因二氢黄酮-4-还原酶 （VvDFR） 和 UDP-葡萄糖类黄酮-3-O 葡萄糖基转移酶 （VvUFGT） 的转录来抑制葡萄浆果和烟草 （Nicotiana tabacum） 中花青素的积累。此外，VvMYB44-1 和 VvWDR2 之间的相互作用竞争性地抑制了 MYB-bHLH-WD40 （MBW） 激活复合物的形成，削弱了复合物的转录活性，从而减少了花青素的积累。此外，VvMYB44-1 通过上调细胞分裂素合成基因 lonely guy 8 （VvLOG8） 的表达和抑制细胞分裂素降解基因细胞分裂素氧化酶 4 （VvCKX4） 促进细胞分裂素积累，从而促进细胞分裂素介导的葡萄浆果花青素抑制。此外，随着乙烯反应元件结合因子相关两亲性抑制 （EAR） 基序的缺失，VvMYB44-1 对花青素生物合成及其下游靶基因的抑制作用减弱，表明 EAR 基序对 VvMYB44-1 对葡萄花青素生物合成的抑制作用是必不可少的。这些结果为 VvMYB44-1 在高温介导的葡萄花青素生物合成中的调控网络提供了新的见解。