Like animals, plants accommodate a rich diversity of microbes, typically without discernible disease symptoms. How their pathogenesis is prevented in the host remains obscure. Here, we show that the root-infecting fungus Colletotrichum fructicola of the C. gloeosporioides clade (CgE), isolated from field-grown healthy Brassicaceae plants, inhibits growth of pathogenic fungi in Arabidopsis thaliana, in a phosphate status-dependent manner. Loss of host ethylene signaling or phytoalexins, camalexin or indole glucosinolates, however, allows CgE to display pathogenesis, suggesting host contributions to endophytic CgE colonization and benefit. Compared to a closely-related C. gloeosporioides pathogen (CgP), CgE is characterized by genome expansion and >700 fungal genes (4.34%) specifically induced in the host roots when co-inoculated with CgP, including genes related to fungal secondary metabolism. This may underlie antimicrobial tolerance of CgE and its dominance over pathogenic fungi within the host, pointing to a role for fungus-fungus competition in asymptomatic fungal colonization in plants.

中文翻译：

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宿主依赖性真菌-真菌竞争抑制拟南芥中真菌的发病机理

像动物一样，植物可以容纳多种微生物，通常没有明显的疾病症状。如何在宿主中预防其发病机制仍然不清楚。在这里，我们表明，从田间生长的健康十字花科植物中分离出的C. gloeosporioides枝（CgE）根部感染真菌炭疽菌（Colletotrichum fructicola），以磷酸盐状态依赖的方式抑制了拟南芥中致病真菌的生长。然而，宿主乙烯信号传导或植物抗毒素，camalexin或吲哚芥子油苷的丢失使CgE表现出发病机理，表明宿主对内生CgE定植和受益的贡献。与紧密相关的球孢梭菌相比病原体（CgP），CgE的特征是基因组扩展和与CgP共同接种时在宿主根部特异性诱导的> 700个真菌基因（4.34％），包括与真菌次级代谢有关的基因。这可能是对CgE的抗菌耐受性及其对宿主内病原真菌的主导作用，表明真菌-真菌竞争在植物无症状真菌定殖中的作用。