Huang Qianmin, Yan Yali, Zhang Xue, Cao Xuejiao, Ludlow Richard, Lu Min, An Huaming
Guizhou Engineering Research Center for Fruit Crops, Agricultural College, Guizhou University, Guiyang, Guizhou, China.
School of Biosciences, Cardiff University, Sir Martin Evans Building, Museum Avenue, Cardiff, UK.
Plant Physiol. 2024 Dec 23;197(1). doi: 10.1093/plphys/kiaf014.
Light plays an important role in determining the l-ascorbate (AsA) pool size in plants, primarily through the transcriptional regulation of AsA metabolism-related genes. However, the specific mechanism of transcriptional induction responsible for light-dependent AsA biosynthesis remains unclear. In this study, we used a promoter sequence containing light-responsive motifs from GDP-L-galactose phosphorylase 2 (RrGGP2), a key gene involved in AsA overproduction in Rosa roxburghii fruits, to identify participating transcription factors. Among these factors, Cycling Dof Factor 3 (RrCDF3) was highly responsive to variations in light intensity, quality, and photoperiod, leading to alterations in RrGGP2 expression. Further yeast one-hybrid and dual-luciferase assays confirmed that RrCDF3 acts as a transcriptional activator of RrGGP2 by binding specifically to its promoter. Modulating the expression of RrCDF3 in fruits through transient overexpression and silencing resulted in significant changes in RrGGP2 expression and AsA synthesis. Additionally, the stable overexpression of RrCDF3 in R. roxburghii calli and Solanum lycopersicum plants resulted in a significant increase in AsA content. Notably, the well-known photo-signal transcription factor ELONGATED HYPOCOTYL5 (RrHY5) directly interacted with the RrCDF3 promoter, enhancing its transcription. These findings reveal a special mechanism involving the RrHY5-RrCDF3-RrGGP2 module that mediates light-induced AsA biosynthesis in R. roxburghii fruit.
光在决定植物中L-抗坏血酸（AsA）库大小方面起着重要作用，主要是通过对AsA代谢相关基因的转录调控。然而，负责光依赖型AsA生物合成的转录诱导具体机制仍不清楚。在本研究中，我们使用了一个包含来自GDP-L-半乳糖磷酸化酶2（RrGGP2）的光响应基序的启动子序列，RrGGP2是参与刺梨果实中AsA过量产生的关键基因，以鉴定参与的转录因子。在这些因子中，循环Dof因子3（RrCDF3）对光强度、光质和光周期的变化高度敏感，导致RrGGP2表达发生改变。进一步的酵母单杂交和双荧光素酶测定证实，RrCDF3通过特异性结合其启动子而作为RrGGP2的转录激活因子。通过瞬时过表达和沉默来调节果实中RrCDF3的表达，导致RrGGP2表达和AsA合成发生显著变化。此外，RrCDF3在刺梨愈伤组织和番茄植株中的稳定过表达导致AsA含量显著增加。值得注意的是，著名的光信号转录因子伸长下胚轴5（RrHY5）直接与RrCDF3启动子相互作用，增强其转录。这些发现揭示了一种特殊机制，即RrHY5-RrCDF3-RrGGP2模块介导刺梨果实中光诱导的AsA生物合成。
