Abstract

Stripe (yellow) rust, caused by the biotrophic fungal pathogen Puccinia striiformis f. sp. tritici (Pst), is emerging as a serious threat to wheat (Triticum aestivum L.) production in many regions of North America. Genetic resistance to stripe rust is typically conditioned by the products of resistance genes that detect pathogen-associated molecular patterns and initiate a cascade of signalling events, culminating in the generation of reactive oxygen species (ROS) and a hypersensitive response (HR) that eventually suppress the pathogen. Complete resistance with no symptoms (immunity response) has also been observed, but less frequently, in certain Pst-wheat interactions. However, such HR-independent resistance responses to Pst have not been well studied. Here we report that the Pst-resistant near isogenic line Avocet-Yr15 (carrying the Yr15 resistance gene) exhibited an immunity response to an isolate of Pst collected in Elora, Ontario, while the Avocet-S line (lacking Yr15) was highly susceptible to the same isolate. In particular, histochemical assays of defence-associated ROS generation and HR were negative during the early stages of the interaction between Pst and the resistant Avocet-Yr15. Microscopic analysis indicated that the pathogen was not able to penetrate the stomata of Avocet-Yr15. Moreover, RNA-sequencing of the immunity response of Avocet-Yr15 to Pst highlighted the activation of a global anti-oxidative-stress response consisting of genes involved in the maintenance of cell viability, redox homoeostasis and photosynthesis. These results provide insights into the molecular mechanisms controlling the immunity response to stripe rust of wheat.

摘要

条纹（黄色）锈病，由生物营养性真菌病原体Puccinia striiformis f 引起。sp. 小麦(Pst) 正在成为对小麦 ( Triticum aestivum ) 的严重威胁L.) 在北美许多地区生产。对条锈病的遗传抗性通常由检测病原体相关分子模式并启动级联信号事件的抗性基因产物调节，最终产生活性氧 (ROS) 和过敏反应 (HR)，最终抑制病原体。在某些 Pst-小麦相互作用中也观察到了没有症状的完全抗性（免疫反应），但频率较低。然而，对 Pst 的这种与 HR 无关的抗性反应尚未得到很好的研究。在这里我们报告了 Pst 抗性近等基因系 Avocet -Yr15（携带Yr15抗性基因）对收集在安大略省埃洛拉的 Pst 分离株表现出免疫反应，而 Avocet-S 系（缺乏Yr15）对同一分离株高度敏感。特别是，在 Pst 与抗性 Avocet -Yr15相互作用的早期阶段，防御相关 ROS 生成和 HR 的组织化学分析为阴性。显微分析表明病原体不能穿透 Avocet -Yr15的气孔。此外，Avocet -Yr15免疫反应的 RNA 测序to Pst 强调了全球抗氧化应激反应的激活，该反应由参与维持细胞活力、氧化还原稳态和光合作用的基因组成。这些结果提供了对控制小麦条锈病免疫反应的分子机制的见解。