Biotechnology Research Center, Southwest University, Chongqing, P.R. China.
Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, Florida, United States of America.
PLoS Pathog. 2020 Apr 23;16(4):e1008518. doi: 10.1371/journal.ppat.1008518. eCollection 2020 Apr.
Competition is one of the fundamental driving forces of natural selection. Beauveria bassiana is a soil and plant phylloplane/root fungus capable of parasitizing insect hosts. Soil and plant environments are often enriched with other fungi against which B. bassiana competes for survival. Here, we report an antifungal peptide (BbAFP1), specifically expressed and localized to the conidial cell wall and is released into the surrounding microenvironment inhibiting growth of competing fungi. B. bassiana strains expressing BbAFP1, including overexpression strains, inhibited growth of Alternaria brassicae in co-cultured experiments, whereas targeted gene deletion of BbAFP1 significantly decreased (25%) this inhibitory effect. Recombinant BbAFP1 showed chitin and glucan binding abilities, and growth inhibition of a wide range of phytopathogenic fungi by disrupting membrane integrity and eliciting reactive oxygen species (ROS) production. A phenylalanine residue (F50) contributes to chitin binding and antifungal activity, but was not required for the latter. Expression of BbAFP1 in tomato resulted in transgenic plants with enhanced resistance to plant fungal pathogens. These results highlight the importance of fungal competition in shaping primitive competition strategies, with antimicrobial compounds that can be embedded in the spore cell wall to be released into the environment during the critical initial phases of germination for successful growth in its environmental niche. Furthermore, these peptides can be exploited to increase plant resistance to fungal pathogens.
竞争是自然选择的基本驱动力之一。球孢白僵菌是一种土壤和植物叶层/根真菌，能够寄生昆虫宿主。土壤和植物环境通常富含其他真菌，球孢白僵菌与之竞争以求得生存。在这里，我们报告了一种抗真菌肽（BbAFP1），它特异性地表达并定位于分生孢子细胞壁上，并释放到周围微环境中，抑制竞争真菌的生长。表达 BbAFP1 的球孢白僵菌菌株，包括过表达菌株，在共培养实验中抑制了芸薹链格孢的生长，而 BbAFP1 的靶向基因缺失则显著降低了（25%）这种抑制作用。重组 BbAFP1 显示出对几丁质和葡聚糖的结合能力，并通过破坏膜完整性和引发活性氧（ROS）产生来抑制广泛的植物病原真菌的生长。一个苯丙氨酸残基（F50）有助于几丁质结合和抗真菌活性，但不是后者所必需的。在番茄中表达 BbAFP1 导致转基因植物对植物真菌病原体的抗性增强。这些结果强调了真菌竞争在塑造原始竞争策略中的重要性，其中抗菌化合物可以嵌入孢子细胞壁中，并在关键的初始萌发阶段释放到环境中，以在其环境小生境中成功生长。此外，这些肽可以被利用来增加植物对真菌病原体的抗性。
