Molecular basis of virulence in tan spot of wheat

小麦褐斑病是小麦的一种重要经济病害，由小麦黑粉病病原菌引起。通常情况下，真菌攻击叶片，导致形成由死亡(坏死)和/或黄色(褪绿)组织组成的病变或斑点。这些症状是由真菌产生的寄主特有的毒素造成的，这种毒素可以攻击一些小麦品种，但不会攻击其他品种。其中一种毒素，PTR ToxB，会导致敏感小麦叶片的黄化。不同菌株产生PTR ToxB的能力不同，这种毒素是由真菌DNA中一种名为ToxB的基因编码的；毒素产生的减少和毒素序列(分子组成)的差异可能会导致导致黄化的能力降低。此外，表达毒素B水平较低的菌株也产生较少的感染性结构，这是真菌攻击植物能力的一般指标。为了进一步了解小麦赤霉菌的致病能力及其与小麦的相互作用，我们将：(1)通过沉默该基因在致病菌株中的表达，研究该真菌的一般致病能力及其与ToxB/PTR ToxB的关系；(2)从所有具有该基因或相关形式的真菌菌株中鉴定ToxB；以及(3)分离和鉴定PTR ToxC，这是从该真菌中预测但从未纯化的另一种诱导黄化的毒素。这项研究不仅有助于解释小麦赤霉病的致病力，而且可能有助于开发基于知识的控制褐斑病的策略，从而使加拿大的农业受益。

The fungal pathogen Pyrenophora tritici-repentis causes tan spot, an economically important disease of wheat. Typically, the fungus attacks the leaves, causing the formation of lesions or spots that consist of dead (necrotic) and/or yellow (chlorotic) tissue. These symptoms result from the production, by the fungus, of host-specific toxins that can attack some wheat varieties but not others. One of these toxins, Ptr ToxB, causes the development of chlorosis on sensitive wheat leaves. Strains of P. tritici-repentis differ in their ability to produce Ptr ToxB, which is encoded in the fungal DNA by a gene called ToxB; decreased toxin production and differences in toxin sequence (molecular composition) can result in a reduced ability to cause chlorosis. In addition, strains that express ToxB at a lower level also produce fewer infective structures, which are general indicators of the capacity of a fungus to attack plants. In order to further understand the disease-causing ability of P. tritici-repentis and its interaction with wheat, we will: (1) investigate general pathogenic ability in the fungus and its relationship to ToxB/Ptr ToxB, by silencing expression of this gene in a virulent isolate, (2) characterize ToxB from all fungal strains that possess this gene or related forms, and (3) isolate and characterize Ptr ToxC, another chlorosis-inducing toxin predicted but never purified from this fungus. The research will not only help explain virulence in P. tritici-repentis, but may also contribute to the development of knowledge-based strategies for controlling tan spot, thereby benefiting the Canadian agricultural industry.