南湖新闻网讯（通讯员 商祥明）近日，华中农业大学果蔬园艺作物种质创新与利用全国重点实验室、湖北洪山实验室柑橘逆境应答与品质调控研究团队研究成果以“The CtrCBL1/CtrCIPK6 Complex of Citrus Phosphorylates CtrBBX32 to Regulate CtrSTP1-mediated Sugar Accumulation and Cold Tolerance”为题在Advacned Science发表。研究揭示了钙信号调控模块CtrCBL1/CtrCIPK6-CtrBBX32 促进根系糖转运蛋白CtrSTP1高表达，从而提升可溶性糖积累、增强柑橘抗寒性的分子路径，为理解逆境下植物碳源分配和根系糖运输积累提供了新见解，也为改良植物抗寒性提供关键功能基因。

温度是影响植物生长发育的关键环境因素，低温对作物产量和地理分布造成重要限制。柑橘是我国南方重要的果树，喜温畏寒，冬季低温常对柑橘产业造成威胁。因此，解析柑橘抗寒应答机制，提升其抗寒能力是重要的产业需求。提高可溶性糖含量是植物应对低温逆境的重要策略，而多年生果树常采用嫁接栽培，砧木根系如何响应低温增强可溶性糖积累和抗寒性的机制仍知之甚少。

▲图1. CtrSTP1表达及其糖转运功能分析

本研究通过挖掘柑橘砧木枳低温处理转录组筛选到一个被显著诱导的糖转运蛋白编码基因CtrSTP1，并且其在根皮层薄壁细胞中特异高表达。亚细胞定位及底物吸收实验表明CtrSTP1蛋白定位于细胞膜且具有己糖转运功能（图1）。转基因材料生理表型证明，CtrSTP1高表达可促进低温下可溶性糖积累并提升柑橘抗寒能力，沉默其表达则表型相反，说明CtrSTP1是柑橘砧木应对低温的重要基因。

▲图2. CtrSTP1调控糖积累增强柑橘抗寒性的分子路径

利用CtrSTP1启动子为诱饵进行酵母单杂交筛库，挖掘到其上游的两个转录因子CtrZAT10和CtrBBX32。生化实验和转基因材料生理表型证明CtrZAT10作为转录激活子促进CtrSTP1的表达，增强枳的耐寒性；而CtrBBX32则作为转录抑制子同时降低CtrSTP1、CtrZAT10的转录水平，破坏枳的耐寒性。为进一步阐明低温下植物如何打破CtrBBX32的转录抑制效应，通过酵母双杂交筛选到与CtrBBX32互作的钙信号响应蛋白激酶 CtrCIPK6，该激酶可以磷酸化CtrBBX32的丝氨酸（Ser）108位点，促进低温环境下的蛋白降解，解除其对CtrSTP1的转录抑制作用（图2）。以上内容阐明了正、负转录因子及钙信号成员调控糖转运蛋白表达的分子路径，系统解析了低温环境下柑橘砧木根系糖积累和稳态调控的创新机制，为柑橘抗寒改良提供重要参考和理论依据。

华中农业大学园艺林学学院博士研究生商祥明为论文第一作者，刘继红教授、李春龙教授为论文共同通讯作者。本研究得到了国家重点研发计划项目、国家自然科学基金项目等项目资助。

论文链接：https://advanced.onlinelibrary.wiley.com/doi/10.1002/advs.202508372

英文摘要

Sugar accumulation is a crucial adaptive strategy for plant cold tolerance, yet its regulatory mechanisms in the roots under cold conditions remain largely unclear. Here, we identified a cold-inducible sugar transporter protein (CtrSTP1), which was highly expressed in the roots of trifoliate orange (Citrus trifoliata L.). CtrSTP1 functioned positively in cold tolerance by facilitating sugar accumulation in the roots. Two transcription factors, CtrBBX32 and CtrZAT10, bound to the CtrSTP1 promoter, with CtrBBX32 acting as transcriptional repressor and CtrZAT10 as activator. CtrBBX32 also suppressed CtrZAT10 expression. Accordingly, CtrBBX32 and CtrZAT10 acted as negative and positive regulators, respectively, of cold tolerance by modulating CtrSTP1 expression. Moreover, CtrCBL1 and CtrCIPK6 formed a complex to phosphorylate CtrBBX32 and promoted its protein degradation, leading to relief of CtrBBX32-mediated repression on CtrZAT10 and CtrSTP1. Further transgenic evidence confirmed that CtrCIPK6 played a positive role in cold tolerance through modulating the sugar pathway. Taken together, these findings uncover a novel regulatory module composed of CtrCBL1/CtrCIPK6-CtrBBX32 that controls cold-induced sugar accumulation by directly or indirectly (via CtrZAT10) modulating the expression of the root-localized CtrSTP1. Our work provides valuable knowledge to advance the understanding of sugar transport and homeostasis in the roots when plants are exposed to adverse environments.

审核人：刘继红 李春龙