Li Yawei, Liu Ziang, Liao Guanglian, Huang Yue, Liu Shengjun, Liu Xukai, Wang Shuting, Liu Bing, He Chunyang, Yang Kun, Xu Yuantao, Zuo Hao, Fu Jialing, Song Lizhi, Li Runhui, Zheng Qianming, Zhang Fei, Lin Zongcheng, Ning Guogui, Xie Zongzhou, Deng Xiuxin, Wang Xia, Xu Qiang
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, Wuhan 430070, P.R. China; Hubei Hongshan Laboratory, Wuhan 430070, P.R. China.
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, Wuhan 430070, P.R. China.
Plant Commun. 2025 Aug 11;6(8):101419. doi: 10.1016/j.xplc.2025.101419. Epub 2025 Jun 16.
The fruit of chestnut rose (Rosa roxburghii Tratt.) contains exceptionally high levels of L-ascorbic acid (AsA) (∼1762 mg/100 g fresh weight), approximately 40-fold higher than those found in sweet orange (Citrus sinensis), which is well known for its high AsA content. However, the molecular mechanisms driving such high accumulation in chestnut rose remain unclear. Here, we report that the genes R. roxburghiiPECTIN METHYLESTERASE (RroxPME), D-GALACTURONATE REDUCTASE (RroxGalUR), and DEHYDROASCORBATE REDUCTASE 2 (RroxDHAR2) play crucial roles in AsA accumulation in chestnut rose fruit. By comparing R. roxburghii with the closely related Rosamultiflora, which has low AsA concentrations, we identified a 545-bp insertion in the promoter of RroxGalUR. We found that TRANSPARENT TESTA GLABRA 2 (RroxTTG2), a well-known key regulator of trichome development, binds to the W-box-containing inserted region of the RroxGalUR promoter as well as the promoters of RroxPME and RroxDHAR2. In contrast, in sweet orange, CsTTG2 can bind only to CsPME. Furthermore, RroxTTG2 retains its conserved role in the regulation of trichome development during early fruit development, suggesting its spatiotemporal specificity in regulating both trichome development and AsA biosynthesis. To evaluate the application value of this pathway in other species, we heterologously expressed RroxTTG2, RroxPME, RroxGalUR, and RroxDHAR2 in lettuce (Lactuca sativa L.), which increased AsA concentrations in the transgenic lines by up to 355% (an increase from approximately 2 to 10 mg/100 g fresh weight). This study provides insights into mechanisms underlying AsA accumulation in chestnut rose and the spatiotemporal transcriptional regulation of AsA biosynthesis and trichome development.
刺梨（Rosa roxburghii Tratt.）果实中L-抗坏血酸（AsA）含量极高（约1762毫克/100克鲜重），约为以高AsA含量而闻名的甜橙（Citrus sinensis）的40倍。然而，刺梨中驱动如此高积累的分子机制仍不清楚。在此，我们报道刺梨果胶甲酯酶基因（RroxPME）、D-半乳糖醛酸还原酶基因（RroxGalUR）和脱氢抗坏血酸还原酶2基因（RroxDHAR2）在刺梨果实AsA积累中起关键作用。通过将刺梨与AsA浓度较低的近缘种多花蔷薇进行比较，我们在RroxGalUR启动子中鉴定出一个545碱基对的插入。我们发现，透明表皮毛光滑2基因（RroxTTG2），一种众所周知的表皮毛发育关键调节因子，可与RroxGalUR启动子以及RroxPME和RroxDHAR2启动子中含W-box的插入区域结合。相比之下，在甜橙中，CsTTG2只能与CsPME结合。此外，RroxTTG2在果实发育早期对表皮毛发育的调控中保留了其保守作用，表明其在调控表皮毛发育和AsA生物合成方面具有时空特异性。为了评估该途径在其他物种中的应用价值，我们在生菜（Lactuca sativa L.）中异源表达了RroxTTG2、RroxPME、RroxGalUR和RroxDHAR2，这使转基因株系中的AsA浓度提高了355%（从约2毫克/100克鲜重增加到10毫克/100克鲜重）。本研究为刺梨中AsA积累的机制以及AsA生物合成和表皮毛发育的时空转录调控提供了见解。
