Plant pathogenic fungi colonizing living plant tissue secrete a cocktail of effector proteins to suppress plant immunity and reprogramme host cells. Although many of these effectors function inside host cells, delivery systems used by pathogenic bacteria to translocate effectors into host cells have not been detected in fungi. Here, we show that five unrelated effectors and two membrane proteins from Ustilago maydis, a biotrophic fungus causing smut disease in corn, form a stable protein complex. All seven genes appear co-regulated and are only expressed during colonization. Single mutants arrest in the epidermal layer, fail to suppress host defence responses and fail to induce non-host resistance, two reactions that likely depend on translocated effectors. The complex is anchored in the fungal membrane, protrudes into host cells and likely contacts channel-forming plant plasma membrane proteins. Constitutive expression of all seven complex members resulted in a surface-exposed form in cultured U. maydis cells. As orthologues of the complex-forming proteins are conserved in smut fungi, the complex may become an interesting fungicide target.

定殖在活植物组织中的植物病原真菌会分泌一种效应蛋白混合物，以抑制植物免疫并重新编程宿主细胞。尽管许多这些效应子在宿主细胞内起作用，但尚未在真菌中检测到病原菌用来将效应子转移到宿主细胞中的传递系统。在这里，我们展示了来自玉米黑粉病的五个不相关的效应子和两个膜蛋白，一种在玉米中引起黑穗病的生物营养真菌，形成稳定的蛋白质复合物。所有七个基因似乎共同调节并且仅在定植期间表达。单个突变体停滞在表皮层，无法抑制宿主防御反应，也无法诱导非宿主抵抗，这两种反应可能取决于易位效应子。该复合物锚定在真菌膜上，伸入宿主细胞并可能接触形成通道的植物质膜蛋白。所有七个复杂成员的本构表达导致在培养的美国玉米细胞中的表面暴露形式。由于形成复合物的蛋白质的直系同源物在黑穗病真菌中是保守的，因此该复合物可能成为一个有趣的杀真菌剂靶标。