Apple leaf spot, caused by Alternaria alternata f. sp mali (ALT), poses a substantial threat to the global apple (Malus × domestica Borkh.) industry. Fungal effectors promote pathogen infestation and survival by interfering with plant immune responses. In our study, we investigated the secretion of effector proteins by the virulent ALT7 strain. Using mass spectrometry, we identified the effector AaAlta1, which belongs to the Alt a 1 protein family (AA1s). Further analysis confirmed that ALT7 secretes AaAlta1. AaAlta1 knockdown mutants displayed reduced pathogenicity in apple tissue culture seedlings, while overexpression strains exhibited enhanced pathogenicity compared to the wild-type ALT7 strain. Using immunoprecipitation followed by mass spectrometry, we isolated pathogenesis-related protein 10-2 (PR10-2) as an interaction partner of AaAlta1 in apple. Knockdown mutants of AaAlta1 showed increased PR10-2-mediated callose deposition in apple, a critical plant defense response. The enhanced defense responses in apple substantially reduced their susceptibility to infection by these ALT7 mutants. Our findings delineate an infection strategy whereby ALT7 secretes AaAlta1 to suppress PR10-2, thereby circumventing the apple defense system.

中文翻译：

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真菌效应子 AaAlta1 抑制苹果中与细胞生成相关的 PROTEIN10-2 介导的胼胝质沉积和防御反应


由链格孢菌 （ALT） 引起的苹果叶斑病对全球苹果 （Malus × domestica Borkh.） 行业构成重大威胁。真菌效应器通过干扰植物免疫反应来促进病原体感染和存活。在我们的研究中，我们研究了毒性 ALT7 菌株分泌效应蛋白。使用质谱法，我们鉴定了效应子 AaAlta1，它属于 Alt a 1 蛋白家族 （AA1s）。进一步分析证实 ALT7 分泌 AaAlta1。与野生型 ALT7 菌株相比，AaAlta1 敲低突变体在苹果组织培养幼苗中的致病性降低，而过表达菌株表现出增强的致病性。使用免疫沉淀和质谱法，我们分离了发病机制相关蛋白 10-2 （PR10-2） 作为苹果中 AaAlta1 的相互作用伴侣。AaAlta1 的敲低突变体显示 PR10-2 介导的胼胝质沉积在苹果中增加，这是一种关键的植物防御反应。苹果中增强的防御反应大大降低了它们对这些 ALT7 突变体感染的易感性。我们的研究结果描述了一种感染策略，其中 ALT7 分泌 AaAlta1 以抑制 PR10-2，从而绕过苹果防御系统。