Summary Ustilago maydis is a biotrophic pathogen causing smut disease in maize. It secretes a cocktail of effector proteins, which target different host proteins during its biotrophic stages in the host plant. One such class of proteins we identified previously is TOPLESS (TPL) and TOPLESS‐RELATED (TPR) transcriptional corepressors. Here, we screened 297 U. maydis effector candidates for their ability to interact with maize TPL protein RAMOSA 1 ENHANCER LOCUS 2 LIKE 2 (RELK2) and their ability to induce auxin signaling and thereby identified three novel TPL‐interacting protein effectors (Tip6, Tip7, and Tip8). Structural modeling and mutational analysis allowed the identification of TPL‐interaction motifs of Tip6 and Tip7. In planta interaction between Tip6 and Tip7 with RELK2 occurs mainly in nuclear compartments, whereas Tip8 colocalizes with RELK2 in a compartment outside the nucleus. Overexpression of Tip8 in nonhost plants leads to cell death, indicating recognition of the effector or its activity. By performing infection assays with single and multideletion mutants of U. maydis, we demonstrate a positive role of Tip6 and Tip7 in U. maydis virulence. Transcriptional profiling of maize leaves infected with Tip effector mutants in comparison with SG200 strain suggests Tip effector activities are not merely redundant.

中文翻译：

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冰山一角？胆诱导真菌玉米黑粉菌的三种新型 TOPLESS 相互作用效应器


摘要 玉米黑粉菌 (Ustilago maydis) 是一种生物营养型病原体，可引起玉米黑穗病。它分泌效应蛋白混合物，在宿主植物的生物营养阶段针对不同的宿主蛋白。我们之前发现的一类蛋白质是 TOPLESS (TPL) 和 TOPLESS-RELATED (TPR) 转录辅阻遏物。在这里，我们筛选了 297 个玉米须杆菌效应子候选物，了解它们与玉米 TPL 蛋白 RAMOSA 1 ENHANCER LOCUS 2 LIKE 2 (RELK2) 相互作用的能力以及诱导生长素信号传导的能力，从而鉴定了三种新型 TPL 相互作用蛋白效应子 (Tip6、Tip7)和提示 8)。结构建模和突变分析允许鉴定 Tip6 和 Tip7 的 TPL 相互作用基序。在植物中，Tip6 和 Tip7 与 RELK2 之间的相互作用主要发生在核区室中，而 Tip8 与 RELK2 共定位于核外的区室中。 Tip8 在非寄主植物中的过度表达会导致细胞死亡，表明效应子或其活性被识别。通过对玉米 U 的单缺失和多缺失突变体进行感染测定，我们证明了 Tip6 和 Tip7 在 U 玉米毒力中的积极作用。与 SG200 菌株相比，感染 Tip 效应突变体的玉米叶子的转录谱表明 Tip 效应活性不仅仅是多余的。