Max Planck Institute for Terrestrial Microbiology, Department of Organismic Interactions, Marburg, Germany.
Westfälische Wilhelms-Universität Münster, Institut für Biologie und Biotechnologie der Pflanzen, Münster, Germany.
mBio. 2021 Mar 2;12(2):e03419-20. doi: 10.1128/mBio.03419-20.
The biotrophic fungus harbors a chitin deacetylase (CDA) family of six active genes as well as one pseudogene which are differentially expressed during colonization. This includes one secreted soluble CDA (Cda4) and five putatively glycosylphosphatidylinositol (GPI)-anchored CDAs, of which Cda7 belongs to a new class of fungal CDAs. Here, we provide a comprehensive functional study of the entire family. While budding cells of showed a discrete pattern of chitosan staining, biotrophic hyphae appeared surrounded by a chitosan layer. We purified all six active CDAs and show their activity on different chitin substrates. Single as well as multiple mutants were generated and revealed a virulence defect for mutants lacking We implicated in production of the chitosan layer surrounding biotrophic hyphae and demonstrated that the loss of this layer does not reduce virulence. By combining different mutations, we detected redundancy as well as specific functions for certain CDAs. Specifically, certain combinations of mutations significantly affected virulence concomitantly with reduced adherence, appressorium formation, penetration, and activation of plant defenses. Attempts to inactivate all seven genes simultaneously were unsuccessful, and induced depletion of in a background lacking the other six genes illustrated an essential role of chitosan for cell wall integrity. The basidiomycete causes smut disease in maize, causing substantial losses in world corn production. This nonobligate pathogen penetrates the plant cell wall with the help of appressoria and then establishes an extensive biotrophic interaction, where the hyphae are tightly encased by the plant plasma membrane. For successful invasion and development in plant tissue, recognition of conserved fungal cell wall components such as chitin by the plant immune system needs to be avoided or suppressed. One strategy to achieve this lies in the modification of chitin to chitosan by chitin deacetylases (CDAs). has seven genes. This study reveals discrete as well as redundant contributions of these genes to virulence as well as to cell wall integrity. Unexpectedly, the inactivation of all seven genes is not tolerated, revealing an essential role of chitosan for viability.
生营养真菌 含有一个几丁质脱乙酰酶（CDA）家族的六个活性基因和一个假基因，这些基因在定植过程中表现出差异表达。这包括一个分泌的可溶性 CDA（Cda4）和五个推测的糖基磷脂酰肌醇（GPI）锚定 CDAs，其中 Cda7 属于真菌 CDA 的一个新类别。在这里，我们对整个家族进行了全面的功能研究。当 的出芽细胞显示出几丁质聚糖的离散染色模式时，生营养菌丝似乎被几丁质聚糖层包围。我们纯化了所有六个活性 CDA，并展示了它们在不同几丁质底物上的活性。生成了单个和多个 突变体，并发现缺乏 的突变体表现出毒力缺陷。我们认为 参与了生营养菌丝周围几丁质聚糖层的产生，并证明该层的缺失不会降低毒力。通过结合不同的 突变，我们检测到某些 CDA 的冗余和特定功能。具体而言，某些突变组合对毒力的影响与附着、附着小体形成、穿透和植物防御激活的降低同时发生。同时失活所有七个 基因的尝试均未成功，而在缺乏其他六个 基因的背景下诱导 的耗尽说明了几丁质聚糖对细胞壁完整性的重要作用。担子菌 会引起玉米黑粉病，导致世界玉米产量的大量损失。这种非专性病原体借助附着小体穿透植物细胞壁，然后建立广泛的生营养相互作用，菌丝被植物质膜紧密包裹。为了在植物组织中成功入侵和发育，植物免疫系统需要避免或抑制对保守真菌细胞壁成分（如几丁质）的识别。实现这一目标的一种策略是通过几丁质脱乙酰酶（CDA）将几丁质修饰为几丁聚糖。 有七个 基因。本研究揭示了这些基因对毒力以及细胞壁完整性的离散和冗余贡献。出乎意料的是，失活所有七个基因是不可容忍的，这表明几丁质聚糖对生存至关重要。
