Wang X, McCallum B D, Fetch T, Bakkeren G, Saville B J
First, second, and third authors: Cereal Research Centre, Agriculture and Agri-Food Canada, 101 Route 100, Morden, MB, R6M 1Y5, Canada; fourth author: Pacific Agri-Food Research Centre, Agriculture and Agri Food Canada, Summerland, BC, VOH 1ZO, Canada; and fifth author: Forensic Science Program, and Environmental and Life Sciences Graduate Program Trent University, Peterborough, ON, K9J 7B8, Canada.
Phytopathology. 2015 Jun;105(6):728-37. doi: 10.1094/PHYTO-08-14-0213-R. Epub 2015 Jun 9.
Race-specific resistance of wheat to Puccinia graminis f. sp. tritici is primarily posthaustorial and often involves the induction of a hypersensitive response (HR). The aim of this study was to investigate host defense responses induced in interactions between P. graminis f. sp. tritici races and wheat lines carrying different race-specific stem rust resistance (Sr) genes. In incompatible interactions between wheat lines carrying Sr36 in three genetic backgrounds (LMPG, Prelude, or W2691) and avirulent P. graminis f. sp. tritici races MCCFC or RCCDM, callose accumulated within 24 h in wheat guard cells contacted by a P. graminis f. sp. tritici appressorium, and P. graminis f. sp. tritici ingress was inhibited following appressorium formation. Accordingly, the expression of transcripts encoding a callose synthase increased in the incompatible interaction between LMPG-Sr36 and avirulent P. graminis f. sp. tritici race MCCFC. Furthermore, the inhibition of callose synthesis through the infiltration of 2-deoxy-D-glucose (DDG) increased the ability of P. graminis f. sp. tritici race MCCFC to infect LMPG-Sr36. A similar induction of callose deposition in wheat guard cells was also observed within 24 h after inoculation (hai) with avirulent P. graminis f. sp. tritici race HKCJC on LMPG-Sr5 plants. In contrast, this defense response was not induced in incompatible interactions involving Sr6, Sr24, or Sr30. Instead, the induction of an HR and cellular lignification were noted. The manifestation of the HR and cellular lignification was induced earlier (24 hai) and was more extensive in the resistance response mediated by Sr6 compared with those mediated by Sr24 or Sr30. These results indicate that the resistance mediated by Sr36 is similar to that mediated by Sr5 but different from those triggered by Sr6, Sr24, or Sr30. Resistance responses mediated by Sr5 and Sr36 are prehaustorial, and are a result of very rapid recognition of molecules derived from avirulent isolates of P. graminis f. sp. tritici, in contrast to the responses triggered in lines with Sr6, Sr24, and Sr30.
小麦对小麦秆锈病菌（Puccinia graminis f. sp. tritici）的小种特异性抗性主要是吸器后抗性，且常常涉及过敏反应（HR）的诱导。本研究的目的是调查在小麦秆锈病菌小种与携带不同小种特异性秆锈病抗性（Sr）基因的小麦品系之间的互作中所诱导的寄主防御反应。在三种遗传背景（LMPG、Prelude或W2691）下携带Sr36的小麦品系与无毒力的小麦秆锈病菌小种MCCFC或RCCDM的不亲和互作中，在小麦保卫细胞中，当小麦秆锈病菌附着胞接触后24小时内胼胝质就会积累，并且在附着胞形成后小麦秆锈病菌的侵入受到抑制。因此，在LMPG-Sr36与无毒力的小麦秆锈病菌小种MCCFC的不亲和互作中，编码胼胝质合成酶的转录本表达增加。此外，通过渗入2-脱氧-D-葡萄糖（DDG）抑制胼胝质合成，增强了小麦秆锈病菌小种MCCFC感染LMPG-Sr36的能力。在用无毒力的小麦秆锈病菌小种HKCJC接种LMPG-Sr5植株后24小时内，也观察到了小麦保卫细胞中胼胝质沉积的类似诱导现象。相反，在涉及Sr6、Sr24或Sr30的不亲和互作中未诱导这种防御反应。取而代之的是，观察到了过敏反应和细胞木质化的诱导。与由Sr24或Sr30介导的抗性反应相比，由Sr6介导的抗性反应中，过敏反应和细胞木质化的表现诱导得更早（接种后24小时）且更广泛。这些结果表明，Sr36介导的抗性与Sr5介导的抗性相似，但与Sr6、Sr24或Sr30引发的抗性不同。Sr5和Sr36介导的抗性反应是吸器前抗性，是对来自无毒力的小麦秆锈病菌分离株的分子进行非常快速识别的结果，这与在携带Sr6、Sr24和Sr30的品系中引发的反应不同。
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