Botanical Institute and Cluster of Excellence on Plant Sciences (CEPLAS), University of Cologne, BioCenter, Zuelpicher Str. 47a, 50674, Cologne, Germany.
Institute for Microbiology, Heinrich Heine University, Universitätsstraße 1, 40225, Düsseldorf, Germany.
New Phytol. 2018 Oct;220(1):249-261. doi: 10.1111/nph.15265. Epub 2018 Jun 19.
Fungalysins from several phytopathogenic fungi have been shown to be involved in cleavage of plant chitinases. While fungal chitinases are responsible for cell wall remodeling during growth and morphogenesis, plant chitinases are important components of immunity. This study describes a dual function of the Ustilago maydis fungalysin UmFly1 in modulation of both plant and fungal chitinases. Genetic, biochemical and microscopic experiments were performed to elucidate the in vitro and in planta functions of U. maydis UmFly1. U. maydis ∆umfly1 mutants show significantly reduced virulence, which coincides with reduced cleavage of the maize chitinase ZmChiA within its chitin-binding domain. Moreover, deletion of umfly1 affected the cell separation of haploid U. maydis sporidia. This phenotype is associated with posttranslational activation of the endogenous chitinase UmCts1. Genetic complementation of the ∆umfly1 mutant with a homologous gene from closely related, but nonpathogenic, yeast fully rescued the cell separation defect in vitro, but it could not recover the ∆umfly1 defect in virulence and cleavage of the maize chitinase. We report on the dual function of the secreted fungalysin UmFly1. We hypothesize that co-evolution of U. maydis with its host plant extended the endogenous function of UmFly1 towards the modulation of plant chitinase activity to promote infection.
几种植物病原真菌的真菌溶素已被证明参与了植物几丁质酶的裂解。真菌几丁质酶负责生长和形态发生过程中的细胞壁重塑，而植物几丁质酶是免疫的重要组成部分。本研究描述了玉米黑粉菌真菌溶素 UmFly1 在调节植物和真菌几丁质酶方面的双重功能。进行了遗传、生化和显微镜实验，以阐明 U. maydis UmFly1 的体外和体内功能。U. maydis ∆umfly1 突变体的毒力显著降低，这与玉米几丁质酶 ZmChiA 在其几丁质结合域内的裂解减少相一致。此外，umfly1 的缺失影响了单倍体 U. maydis 分生孢子的细胞分离。这种表型与内源性几丁质酶 UmCts1 的翻译后激活有关。用同源基因对 ∆umfly1 突变体进行遗传互补，可完全恢复体外细胞分离缺陷，但不能恢复 ∆umfly1 对玉米几丁质酶的毒力和裂解缺陷。我们报告了分泌性真菌溶素 UmFly1 的双重功能。我们假设 U. maydis 与其宿主植物的共同进化扩展了 UmFly1 的内源性功能，以调节植物几丁质酶活性，促进感染。
