Anthocyanins are a valuable source of antioxidants in the human diet and contribute to fruit coloration. In red-skinned pears, anthocyanin biosynthesis can be induced by light, in which the MYB–bHLH–WDR complex plays a critically important role in transcriptional regulation. However, the knowledge of WRKY-mediated transcriptional regulation of light-induced anthocyanin biosynthesis is scarce in red pears. This work identified and functionally characterized a light-inducing WRKY TF, PpWRKY44, in pear. Functional analysis based on overexpressed pear calli showed that PpWRKY44 promoted anthocyanin accumulation. Also, transiently overexpressed PpWRKY44 in pear leaves and fruit peels significantly enhanced the accumulation of anthocyanin, whereas silencing PpWRKY44 in pear fruit peels impaired induction of the accumulation of anthocyanin by light. By chromatin immunoprecipitation and electrophoretic mobility shift assay coupled to a quantitative polymerase chain reaction, we found that PpWRKY44 bound in-vivo and in-vitro to the PpMYB10 promoter, revealing it as a direct downstream target gene. Moreover, PpWRKY44 was activated by PpBBX18, a light signal transduction pathway component. Our results explained the mechanism mediating the impacts of PpWRKY44 on the transcriptional regulation of anthocyanin accumulation, with potential implications for fine-tuning the fruit peel coloration triggered by light in red pears.

中文翻译：

---

梨光响应转录因子PpWRKY44通过调节PpMYB10表达诱导花青素积累

花青素是人类饮食中抗氧化剂的宝贵来源，有助于水果着色。在红皮梨中，光可以诱导花青素生物合成，其中 MYB-bHLH-WDR 复合物在转录调控中发挥着至关重要的作用。然而，在红梨中，WRKY 介导的光诱导花青素生物合成转录调控的知识却很少。这项工作鉴定了梨中的光诱导 WRKY TF（PpWRKY44）并进行了功能表征。基于过表达梨愈伤组织的功能分析表明，PpWRKY44 促进花青素积累。此外，梨叶和果皮中短暂过表达的PpWRKY44显着增强了花青素的积累，而梨果皮中沉默PpWRKY44则损害了光对花青素积累的诱导。通过染色质免疫沉淀和电泳迁移率变动测定与定量聚合酶链式反应相结合，我们发现 PpWRKY44 在体内和体外与 PpMYB10 启动子结合，揭示其作为直接下游靶基因。此外，PpWRKY44 被光信号转导通路成分 PpBBX18 激活。我们的结果解释了 PpWRKY44 对花青素积累转录调控影响的机制，对于微调红梨中由光触发的果皮着色具有潜在意义。