Zhao Cheng, Mao Ke, You Chun-Xiang, Zhao Xian-Yan, Wang Shu-Hui, Li Yuan-Yuan, Hao Yu-Jin
State Key Laboratory of Crop Biology, Tai-An, Shandong 271018, China; National Research Center for Apple Engineering and Technology, Tai-An, Shandong 271018, China; College of Horticulture Science and Engineering, Shandong Agricultural University, Tai-An, Shandong 271018, China.
College of Biological Science and Technology, Beijing Forestry University, Beijing 100083, China.
Plant Sci. 2016 Jun;247:115-26. doi: 10.1016/j.plantsci.2016.03.006. Epub 2016 Mar 17.
UVR8 (UV Resistance Locus 8) is an ultraviolet-B (UV-B; 280-315nm) light receptor that is involved in regulating many aspects of plant growth and development. UV-B irradiation can increase the development of flower and fruit coloration in many fruit trees, such as grape, pear and apple. Previous investigations of the structure and functions of UVR8 in plants have largely focused on Arabidopsis. Here, we isolated the UVR8 gene from apple (Malus domestica) and analyzed its function in transgenic Arabidopsis. Genomic and protein sequence analysis showed that MdUVR8 shares high similarity with the AtUVR8 protein from Arabidopsis, including the conserved seven-bladed β-propeller, the C27 region, the 3 "GWRHT" motifs and crucial amino-acid residues (14 Trps, 2 Args). A point mutation prediction and three-dimensional structural analysis of MdUVR8 indicated that it has a similar structure to AtUVR8 and that the crucial residues are also important in MdUVR8. In terms of transcript levels, MdUVR8 expression was up-regulated by UV-B light, which suggests that its expression follows a 24-h circadian rhythm. Using heterologous expression of MdUVR8 in both uvr8-1 mutant and wild-type (WT) Arabidopsis, we found that MdUVR8 regulates hypocotyl elongation and gene expression under UV-B light. These data provide functional evidence for a role of MdUVR8 in controlling photomorphogenesis under UV-B light and indicate that the function of UVR8 is conserved between Arabidopsis and apple. Furthermore, we examined the interaction between MdUVR8 and MdCOP1 (constitutive photomorphogenic1) using a yeast two-hybrid assay and a co-immunoprecipitation assay. This interaction provides a direction for investigating the regulatory mechanisms of the UV-B-light pathway in apple.
UVR8（紫外线抗性位点8）是一种紫外线B（UV-B；280-315纳米）光受体，参与调节植物生长和发育的许多方面。UV-B照射可促进许多果树（如葡萄、梨和苹果）的花朵发育和果实着色。此前对植物中UVR8结构和功能的研究主要集中在拟南芥上。在此，我们从苹果（苹果属）中分离出UVR8基因，并分析了其在转基因拟南芥中的功能。基因组和蛋白质序列分析表明，MdUVR8与拟南芥的AtUVR8蛋白具有高度相似性，包括保守的七叶β-螺旋桨、C27区域、3个“GWRHT”基序和关键氨基酸残基（14个色氨酸、2个精氨酸）。MdUVR8的点突变预测和三维结构分析表明，它与AtUVR8具有相似的结构，关键残基在MdUVR8中也很重要。在转录水平上，MdUVR8的表达受UV-B光上调，这表明其表达遵循24小时昼夜节律。通过在uvr8-1突变体和野生型（WT）拟南芥中异源表达MdUVR8，我们发现MdUVR8在UV-B光下调节下胚轴伸长和基因表达。这些数据为MdUVR8在UV-B光下控制光形态建成中的作用提供了功能证据，并表明UVR8的功能在拟南芥和苹果之间是保守的。此外，我们使用酵母双杂交试验和免疫共沉淀试验检测了MdUVR8与MdCOP1（组成型光形态建成1）之间的相互作用。这种相互作用为研究苹果中UV-B光信号通路的调控机制提供了方向。
