Soil beneficial bacteria can effectively inhibit bacterial pathogens by assembling contact-dependent killing weapons, such as the type IVA secretion system (T4ASS). It’s not clear whether these antibacterial weapons are involved in biotrophic microbial interactions in soil. Here we showed that an antifungal antibiotic 2,4-DAPG production of the soil bacterium, Pseudomonas protegens can be triggered by another soil bacterium, Lysobacter enzymogenes, via T4ASS by co-culturing on agar plates to mimic cell-to-cell contact. We demonstrated that the induced 2,4-DAPG production of P. protegens is achieved by intracellular detection of the T4ASS effector protein Le1519 translocated from L. enzymogenes. We defined Le1519 as LtaE (Lysobacter T4E triggering antifungal effects), which specifically stimulates the expression of 2,4-DAPG biosynthesis genes in P. protegens, thereby protecting soybean seedlings from infection by the fungus Rhizoctonia solani. We further found that LtaE directly bound to PhlF, a pathway-specific transcriptional repressor of the 2,4-DAPG biosynthesis, then activated the 2,4-DAPG production. Our results highlight a novel pattern of microbial interspecies and interkingdom interactions, providing a unique case for expanding the diversity of soil microbial interactions.

土壤有益菌可以通过组装接触依赖性杀伤武器，如IVA型分泌系统（T4ASS），有效抑制细菌病原体。目前尚不清楚这些抗菌武器是否参与土壤中生物营养微生物的相互作用。在这里，我们表明，土壤细菌（ Pseudomonas protegens）的抗真菌抗生素 2,4-DAPG 生产可以由另一种土壤细菌（ Lysobacter enzymogenes）触发，通过 T4ASS 在琼脂平板上共培养来模拟细胞与细胞的接触。我们证明， P. protegens诱导产生 2,4-DAPG 是通过细胞内检测从L. enzymogenes转位的 T4ASS 效应蛋白 Le1519 来实现的。我们将Le1519定义为LtaE（溶杆菌T 4E触发抗真菌作用），它特异性刺激P. protegens中2,4-DAPG生物合成基因的表达，从而保护大豆幼苗免受真菌立枯丝核菌的感染。我们进一步发现，LtaE 直接与 2,4-DAPG 生物合成途径特异性转录抑制因子 PhlF 结合，然后激活 2,4-DAPG 的产生。我们的结果突出了微生物种间和界间相互作用的新模式，为扩大土壤微生物相互作用的多样性提供了独特的案例。