Lasiodiplodia theobromae is one of the primary causal agents in peach gummosis disease, leading to enormous losses in peach production. In our previous study, a redox-related gene, LtAP1, from the fungus was significantly upregulated in peach shoots throughout infection. Here, we characterized LtAP1, a basic leucine zipper transcription factor, during peach gummosis progression using the CRISPR-Cas9 system and homologous recombination. The results showed that LtAP1-deletion mutant had slower vegetative growth and increased sensitivity to several oxidative and nitrosative stress agents. LtAP1 was highly induced by exogenous oxidants treatment in the L. theobromae wild-type strain. In a pathogenicity test, the deletion mutant showed decreased virulence (reduced size of necrotic lesions, less gum release, and decreased pathogen biomass) on infected peach shoots compared to the wild-type strain. The mutant showed severely reduced transcription levels of genes related to glutaredoxin and thioredoxin in L. theobroame under oxidative stress or during infection, indicating an attenuated capacity for reactive oxygen species (ROS) detoxification. When shoots were treated with an NADPH oxidase inhibitor, the pathogenicity of the mutant was partially restored. Moreover, ROS production and plant defense response were strongly activated in peach shoots infected by the mutant. These results highlight the crucial role of LtAP1 in the oxidative stress response, and further that it acts as an important virulence factor through modulating the fungal ROS-detoxification system and the plant defense response.

可可豆是桃胶病的主要病原体之一，导致桃生产的巨大损失。在我们之前的研究中，一个氧化还原相关基因，LtAP1，来自真菌在整个感染过程中在桃芽中显着上调。在这里，我们表征了LtAP1，一种基本的亮氨酸拉链转录因子，在桃树胶病进展过程中使用 CRISPR-Cas9 系统和同源重组。结果表明，LtAP1-deletion 突变体的营养生长较慢，对几种氧化和亚硝化应激剂的敏感性增加。 LtAP1 外源性氧化剂处理高度诱导 可可乳杆菌野生型菌株。在致病性测试中，与野生型菌株相比，缺失突变体对受感染桃芽的毒力降低（坏死病灶大小减小，牙龈释放减少，病原体生物量减少）。该突变体显示与谷氧还蛋白和硫氧还蛋白相关的基因转录水平严重降低。可可豆在氧化应激或感染期间，表明活性氧 (ROS) 解毒能力减弱。当用 NADPH 氧化酶抑制剂处理枝条时，突变体的致病性部分恢复。此外，在被突变体感染的桃枝中，ROS 产生和植物防御反应被强烈激活。这些结果强调了LtAP1 在氧化应激反应中，并进一步通过调节真菌 ROS 解毒系统和植物防御反应作为重要的毒力因子。