Apple ring rot, which is caused by Botryosphaeria dothidea, is one of the most devastating diseases of apple. However, the lack of a known molecular resistance mechanism limits the development of resistance breeding. Here, the “Golden Delicious” and ‘Fuji ‘Nagafu No. 2″ apple cultivars were crossed, and a population of 194 F1 individuals was generated. The hybrids were divided into 5 categories according to their differences in B. dothidea resistance during three consecutive years. Quantitative proteomic sequencing was performed to analyze the molecular mechanism of the apple response to B. dothidea infection. Hierarchical clustering and weighted gene coexpression network analysis (WGCNA) revealed that photosynthesis was significantly correlated with the resistance of apple to B. dothidea. The level of chlorophyll fluorescence in apple functional leaves increased progressively as the level of disease resistance improved. However, the content of soluble sugar decreased with the improvement of disease resistance. Further research revealed that sorbitol, the primary photosynthetic product, played major roles in apple resistance to B. dothidea. Increasing the content of sorbitol by overexpressing MdS6PDH1 dramatically enhanced apple calli resistance to B. dothidea by activating the expression of salicylic acid (SA) signaling pathway-related genes. However, decreasing the content of sorbitol by silencing MdS6PDH1 showed the opposite phenotype. Furthermore, exogenous sorbitol treatment partially restored the resistance of MdS6PDH1-RNAi lines to B. dothidea. Taken together, these findings reveal that sorbitol is an important metabolite that regulates the resistance of apple to B. dothidea and offer new insights into the mechanism of plant resistance to pathogens.

中文翻译：

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F1杂种种群的定量蛋白质组学测序揭示山梨糖醇在苹果对葡萄球菌的抗性中的作用

苹果环腐病是由葡萄球菌引起的，是苹果最具破坏性的病害之一。然而，缺乏已知的分子抗性机制限制了抗性育种的发展。在这里，将“金冠”和“富士长府2号”苹果品种杂交，产生了194个F1个体。根据连续3年对B. dothidea的抗性差异，将杂种分为5类。进行定量蛋白质组测序以分析苹果对 B. dothidea 感染反应的分子机制。层次聚类和加权基因共表达网络分析（WGCNA）表明，光合作用与苹果对B. dothidea 的抗性显着相关。随着抗病能力的提高，苹果功能叶中叶绿素荧光水平逐渐升高。但可溶性糖的含量随着抗病能力的提高而降低。进一步的研究表明，主要的光合产物山梨糖醇在苹果对 B. dothidea 的抗性中起主要作用。通过过表达 MdS6PDH1 增加山梨糖醇的含量，通过激活水杨酸 (SA) 信号通路相关基因的表达，显着增强了苹果愈伤组织对 B. dothidea 的抗性。然而，通过沉默 MdS6PDH1 来降低山梨糖醇的含量显示出相反的表型。此外，外源山梨醇处理部分恢复了 MdS6PDH1-RNAi 系对 B. dothidea 的抗性。综合起来，