Characterization of the molecular pathways that direct development and pathogenicity in the vascular wilt fungus Verticillium dahliae

大丽花黄萎病（Verticillium dahliae）是一种丝状真菌，可引起多种重要经济一年生和多年生作物的血管性枯萎病。在感染期间，真菌被限制在植物的导水（维管）系统中，以两种形式生长，如菌丝和酵母样细胞。在疾病的后期，大丽花从血管系统逃到周围的组织中，在那里它产生了生存结构。这些耐寒的色素细胞簇与植物碎片一起分散在土壤中，可以在土壤中存活至少十年，并且是疾病接种的主要来源。参与这些结构发育和植物二态生长的分子途径为疾病控制提供了有吸引力的潜在靶点。在我实验室之前的研究中，我们发现疏水蛋白（疏水蛋白VDH1）和自噬过程（细胞内循环系统）对生存结构的发育都是必不可少的。另一个重要的发现是，VDH1在感染的早期阶段被植物识别并诱导植物防御反应，但植物无法维持这些防御。分子策略将用于解决提出的研究中的两个主要目标。首先是更好地定义生存结构发育途径，并确定途径中可能被阻断的步骤，以阻止植物的生存结构形成和/或病原体定植。第二个目标将是确定尚不明确的大丽花疏水酶在生存、结构发育和植物识别中诱导植物防御的作用。研究将开始确定病原体使用什么分子机制来阻止由病原体识别引发的植物防御反应。本研究结果将为今后开发新的黄萎病防治策略提供参考。所得到的数据也有望与其他病原真菌的研究相关，其中植物维管系统是首选的环境生态位。

Verticillium dahliae is a filamentous fungus that causes vascular wilt of a broad range of economically important annual and perennial crops. During infection the fungus is confined to the plant's water-conducting (vascular) system, growing dimorphically (in two forms), as hyphal and yeast-like cells. In the late stages of disease V. dahliae escapes from the vascular system into the surrounding tissues where it produces its survival structures. These hardy, pigmented clusters of cells are dispersed into the soil with plant debris, can survive for at least a decade in the soil, and are the primary source of disease inoculum. The molecular pathways involved in development of these structures, and in planta dimorphic growth offer attractive potential targets for disease control. In previous studies in my lab we showed that both a hydrophobic protein (hydrophobin VDH1) and the process of autophagy (the cells' intracellular recycling system) are essential for survival structure development. The other important discovery was that VDH1 is recognized by the plant during the early phase of infection to induce plant defence responses, but that the plant is unable to sustain those defences. Molecular strategies will be used to address two major objectives in of the proposed research. The first will be to better define the survival structure developmental pathway, and to identify steps in the pathway that could potentially be blocked to prevent survival structure formation and/or pathogen colonization of the plant. The second objective will be to determine the roles of as-yet uncharacterized V. dahliae hydrophobins during survival structure development and in plant recognition to induce plant defences. Studies will be initiated to determine what molecular mechanism(s) the pathogen uses to thwart the plant defence responses that are triggered by recognition of the pathogen. The results of the proposed research would provide knowledge for future development of new, and badly needed disease control strategies to manage verticillium wilt. The resulting data are also anticipated to be relevant to studies of other pathogenic fungi for which the plant vascular system is the preferred environmental niche.