Xu Xu, Gui Renzhi, Zhu Jialing, Zhang Xiangzhao, Fu Weihong, Zhao Lin, Wang Sanhong
College of Horticulture, Nanjing Agricultural University, Nanjing 210095, China.
Xuzhou Institute of Agricultural Sciences in Xuhuai Region of Jiangsu, Xuzhou 221131, China.
J Agric Food Chem. 2025 Jun 25;73(25):15550-15560. doi: 10.1021/acs.jafc.5c02314. Epub 2025 Jun 12.
Red-fleshed apples have attracted widespread attention for their rich anthocyanin content. However, some red-fleshed apples, such as "Xiahongrou" (), exhibit a decline in red pigmentation and anthocyanin content as the fruit develops. The molecular mechanism underlying this flesh discoloration is poorly understood. In this study, through transcriptome analysis, we identified an R1-type MYB transcription factor, , whose expression exhibited a positive correlation with alterations in flesh anthocyanins during fruit development. Overexpression of significantly enhanced anthocyanin accumulation and upregulated anthocyanin biosynthesis-related structural gene expression through transient expression assays in apple fruit and stable transformation experiments in calli. Conversely, it significantly inhibited the expression of , a known negative regulator of anthocyanin synthesis. In binding experiments, we demonstrated that binds to the promoter of and inhibits its transcription. Additionally, we observed that the C DNA methylation level of the promoter exhibited a gradual increase with fruit development, resulting in a concomitant decrease in its transcriptional level. Together, our results indicate that functions as a repressor upstream of . Elevated methylation levels in the promoter inhibit its transcription, leading to a reduction in the anthocyanin content in the flesh during fruit develops.
红肉苹果因其富含花青素而受到广泛关注。然而，一些红肉苹果品种，如“夏红肉”，在果实发育过程中会出现红色素沉着和花青素含量下降的现象。目前对这种果肉变色的分子机制了解甚少。在本研究中，通过转录组分析，我们鉴定出一个R1型MYB转录因子，其表达与果实发育过程中果肉花青素的变化呈正相关。通过在苹果果实中的瞬时表达试验和愈伤组织中的稳定转化实验，该转录因子的过表达显著增强了花青素的积累，并上调了花青素生物合成相关结构基因的表达。相反，它显著抑制了已知的花青素合成负调控因子的表达。在结合实验中，我们证明该转录因子与该负调控因子的启动子结合并抑制其转录。此外，我们观察到该负调控因子启动子的C DNA甲基化水平随着果实发育而逐渐增加，导致其转录水平随之降低。总之，我们的结果表明该转录因子在该负调控因子上游起抑制作用。该负调控因子启动子甲基化水平的升高抑制了其转录，导致果实发育过程中果肉花青素含量降低。
