禾谷鐮孢菌侵染小麥胚芽鞘的分子策略研究

袁婷露　張曉偉　賈雷杰　江剛　張棟

摘 要：禾谷鐮孢（Fusarium graminearum）是一種絲狀真菌，廣泛侵染多種農作物，禾谷鐮孢的基因組編碼約14000個基因，已有上百個基因被證明與其致病性相關，但禾谷鐮孢致病機制的全貌仍不清楚。該研究組運用激光顯微切割技術和芯片雜交，以小麥赤霉病的病原真菌-禾谷鐮孢為對象，直接從感染的小麥組織中分離出不同侵染階段的禾谷鐮孢，獲得階段特異性的體內生長真菌全基因表達譜；通過發展細胞類型特異性芯片數據分析相關生物信息學方法，系統分析禾谷鐮孢在宿主體內的表達譜動態，觀察到細胞壁降解酶分階段提升、環境活性氧清除先于活性氧分泌、乙醛酸循環早期提升、多種次生代謝物毒素在后期誘導等現象，推導提出禾谷鐮孢侵染小麥胚芽鞘時依次采取隱蔽型胞間延伸、快速胞內生長、公開型全面破壞三種侵染策略轉換，并通過基因敲除及互補等鑒定出多個毒力基因，驗證了提出的侵染策略，揭示了禾谷鐮孢侵染植物分子路線概貌。

關鍵詞：禾谷鐮孢 激光顯微切割 植物細胞壁降解酶

Abstract：The ascomycete Fusarium graminearum is a destructive fungal pathogen of wheat. To better understand how this pathogen proliferates within the host plant， we tracked pathogen growth inside wheat coleoptiles， and then examined pathogen gene expression inside wheat coleoptiles at 16， 40 and 64 hours post-inoculation （hpi） using laser capture microdissection and microarray analysis. A total of 344 genes were identified to be preferentially expressed during hyphal growth in planta. Evaluation of 134 putative plant cell wall degrading enzyme genes suggests limited cell wall degradation at 16 hpi and extensive degradation at 64 hpi. Evaluation of reactive oxygen species （ROS）-related enzymes indicates that F. graminearum primarily scavenges extracellular ROS in advance of a later burst of pathogen-produced extracellular ROS-generating enzymes. The expression patterns of genes involved in primary metabolic pathways suggest that F. graminearum might rely on the glyoxylate cycle at an early stage of plant infection. A novel secondary metabolite biosynthesis gene cluster was specifically induced at 64 hpi and was required for virulence. Our results indicate that F. graminearum initiates infection of coleoptiles using covert growth strategies， and switches to overt cellular destruction of tissues at an advanced stage of infection.

Key Words：Fusarium graminearum；Laser microdissection；Plant cell wall degrading-enzymes

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