Molecular basis of virulence in tan spot of wheat

小麦褐斑病是小麦的一种重要的经济病害。通常情况下，真菌攻击叶子，导致形成病变或斑点，由死亡（坏死）和/或黄色（褪绿）组织组成。这些症状是由真菌产生的宿主特异性毒素引起的，这种毒素可以攻击某些小麦品种，但对其他小麦品种不起作用。其中一种毒素，Ptr ToxB，会导致敏感的小麦叶片发生黄化。tritric -repentis菌株产生Ptr ToxB的能力不同，Ptr ToxB是由一种叫做ToxB的基因编码在真菌DNA中；毒素产生的减少和毒素序列（分子组成）的差异可导致导致黄化的能力降低。此外，表达ToxB水平较低的菌株也产生较少的感染结构，这是真菌攻击植物能力的一般指标。为了进一步了解小麦螺旋体的致病能力及其与小麦的相互作用，我们将：(1)通过在毒力强的分离物中沉默该基因的表达，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；(3)分离并鉴定另一种预测但从未从该真菌中纯化过的致绿毒素Ptr ToxC。这项研究不仅有助于解释小麦黑斑病的毒力，而且可能有助于开发以知识为基础的控制棕斑病的策略，从而使加拿大的农业工业受益。

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.