Abstract：
Salinity is a severe abiotic stress that limits plant survival, growth, and development. 14-3-3 proteins are phosphopeptide-binding proteins that are involved in numerous signaling pathways, such as metabolism, development, and stress responses. However, their roles in salt tolerance are unclear in woody plants. Here, we characterized an apple (Malus domestica) 14-3-3 gene, GENERAL REGULATORY FACTOR 8 (MdGRF8), the product of which promotes salinity tolerance. MdGRF8 overexpression improved salt tolerance in apple plants, whereas MdGRF8-RNA interference (RNAi) weakened it. Yeast 2-hybrid, bimolecular fluorescence complementation, pull-down, and coimmunoprecipitation assays revealed that MdGRF8 interacts with the transcription factor MdWRKY18. As with MdGRF8, overexpressing MdWRKY18 enhanced salt tolerance in apple plants, whereas silencing MdWRKY18 had the opposite effect. We also determined that MdWRKY18 binds to the promoters of the salt-related genes SALT OVERLY SENSITIVE 2 (MdSOS2) and MdSOS3. Moreover, we showed that the 14-3-3 protein MdGRF8 binds to the phosphorylated form of MdWRKY18, enhancing its stability and transcriptional activation activity. Our findings reveal a regulatory mechanism by the MdGRF8-MdWRKY18 module for promoting the salinity stress response in apple.
摘要：
盐度是一种严重的非生物胁迫，限制了植物的生存，增长,和发展。14-3-3蛋白是参与许多信号通路的磷酸肽结合蛋白，比如新陈代谢，发展,和应激反应。然而,在木本植物中，它们在耐盐性中的作用尚不清楚。这里,我们鉴定了苹果（Malusdomestica）14-3-3基因，一般调节因子8(MdGRF8)，其产品促进耐盐性。MdGRF8过表达提高了苹果植株的耐盐性，而MdGRF8-RNA干扰(RNAi)削弱了它。酵母2-杂种，双分子荧光互补，下拉,和共免疫沉淀分析显示MdGRF8与转录因子MdWRKY18相互作用。与MdGRF8一样，过表达MdWRKY18增强了苹果植株的耐盐性，而沉默MdWRKY18则具有相反的效果。我们还确定MdWRKY18与盐相关基因盐过度敏感2(MdSOS2)和MdSOS3的启动子结合。此外，我们发现14-3-3蛋白MdGRF8与MdWRKY18的磷酸化形式结合，增强了其稳定性和转录激活活性。我们的发现揭示了MdGRF8-MdWRKY18模块促进苹果盐度胁迫反应的调节机制。
