摘要：刺梨（Rosa roxburghiiTratt.）果实以其极高的维生素C（L-抗坏血酸，AsA）含量著称，平均积累量达1,762 mg/100 g鲜重，是甜橙（~50 mg/100 g）的40倍，但其分子机制长期未明。AsA作为植物抵御逆境的关键抗氧化剂，其合

华中农大徐强-王霞团队揭示刺梨维生素C合成与果实表皮毛发育的分子调控机制

刺梨（Rosa roxburghiiTratt.）果实以其极高的维生素C（L-抗坏血酸，AsA）含量著称，平均积累量达1,762 mg/100 g鲜重，是甜橙（~50 mg/100 g）的40倍，但其分子机制长期未明。AsA作为植物抵御逆境的关键抗氧化剂，其合成主要依赖L-半乳糖途径，而转运蛋白（如谷胱甘肽-S-转移酶）和调控基因（如GDP-半乳糖醛酸还原酶）在物种间的高积累变异中的作用尚不清晰。前期研究虽鉴定到部分AsA合成相关基因（如GMEGMPGGPDHAR），但刺梨中驱动超量积累的核心调控网络仍未解析，且其果实表面独特的表皮毛（刺状结构）发育与AsA代谢的潜在关联未被探索。

华中农业大学徐强、王霞团队通过比较刺梨（高AsA）与近缘种野蔷薇（R. multiflora，低AsA）的基因组，发现RroxGalUR（GDP-半乳糖醛酸还原酶基因）启动子区存在一段545 bp插入变异，该区域含W-box顺式作用元件；进一步通过酵母单杂交电泳迁移率变动分析（EMSA）及双荧光素酶报告系统验证，表明表皮毛发育关键转录因子RroxTTG2特异性结合该插入序列，并激活RroxGalUR的表达，同时RroxTTG2还能直接结合RroxPME（果胶甲酯酶基因）和RroxDHAR2（脱氢抗坏血酸还原酶基因）的启动子，形成多基因协同调控模块；而在甜橙中，同源基因CsTTG2仅能结合CsPME，无法调控其他AsA合成基因，揭示了刺梨的特异性调控网络。值得注意的是，RroxTTG2在果实发育早期仍保留调控表皮毛形成的功能（通过组织特异性表达验证），表明其具有时空特异性双重角色——早期调控形态建成，后期驱动AsA合成。为验证该通路的应用潜力，研究将RroxTTG2RroxPMERroxGalUR和RroxDHAR2在生菜（Lactuca sativa）中异源共表达，使转基因株系的AsA含量提升355%（从2 mg/100 g增至10 mg/100 g鲜重），直接证实了这些基因的功能协同性。

本研究首次阐明刺梨AsA超量积累的核心机制：RroxTTG2通过结合关键基因启动子中的特异顺式元件，同步调控AsA合成（RroxGalURRroxPMERroxDHAR2）与果实表皮毛发育，且其调控能力因RroxGalUR启动子的545 bp插入而增强。该发现不仅解析了代谢与形态建成的协同进化，还为作物AsA强化育种提供了高效靶点（如RroxTTG2-RroxGalUR模块），有望推动高营养果蔬品种的培育。

Yawei Li, Ziang Liu, Guanglian Liao…… Xiuxin Deng, Xia Wang*, Qiang Xu*

National Key laboratory for Germplasm Innovation & Utilization of Horticultural Crops, Joint International Research Laboratory of Germplasm Innovation & Utilization of Horticultural Crops, College of Horticulture and Forestry Sciences, Huazhong Agricultural University, P.R. China.

Abstract

The chestnut rose (Rosa roxburghiiTratt.) has a high accumulation of L-ascorbic acid (AsA) (∼1,762 mg/100 g fresh weight) in its fruits, around 40-fold that of sweet orange (Citrus sinensis), which is known for AsA concentration in fruit. However, the molecular mechanisms behind this high accumulation remain unclear. Here, we revealed that theRroxPMERroxGalURRroxDHAR2genes play a crucial role in AsA accumulation in chestnut rose fruit. By comparingR.roxburghiiwith the closely relatedR.multiflora, which has a low AsA concentration, we identified a 545 bp insertion in the promoter ofRroxGalUR. We determined that RroxTTG2, a well-known key regulator of trichome development, could bind to the W-box containing inserted region of theRroxGalURpromoter, as well as the promotersRroxPMEandRroxDHAR2.By contrast, in sweet orange, CsTTG2 can only bind to theCsPME.Furthermore, RroxTTG2 retained its conserved role in the regulation of trichome development at the early stage of fruit development, suggesting it has spatiotemporal specificity in regulating both trichome development and AsA biosynthesis. To test the application value of this pathway in other species, we heterologously expressedRroxTTG2RroxPMERroxGalURRroxDHAR2in lettuce (Lactuca sativaL.), which increased the AsA concentration of the transgenic lines by up to 355% (about increase from 2 to 10 mg/100 g FW). Our study provided insights into the mechanisms underlying AsA accumulation in chestnut rose and the spatiotemporal transcriptional regulation of AsA biosynthesis and trichome development.

来源：北村李