在发病过程中,效应蛋白从病原体分泌到宿主植物以提供侵入宿主的毒力活性。然而,一旦宿主工厂识别出其中一个传递的效应器,效应子触发的免疫激活强大的免疫和超敏反应(HR)。在植物中,效应子AvrRps4被加工成N-末端(AvrRps4N)和C-末端(AvrRps4C)。AvrRps4C足以触发萝卜的HR并激活拟南芥中AtRRS1/AtRPS4介导的免疫;另一方面,AvrRps4N诱导莴苣中的HR。此外,AvrRps4N介导的HR需要在位置112(R112)的保守精氨酸,这对于全长AvrRps4(AvrRps4F)处理也很重要。这里,我们表明,对于AvrRps4家族,生菜中的效应器处理和效应器识别是分离的。此外,我们比较了生菜对AvrRps4及其同源物的效应物识别,HopK1和XopO。有趣的是,与AvrRps4和HopK1不同,XopO中保守R111的突变本身不足以消除识别.氨基酸取代精氨酸111到亮氨酸与谷氨酸114到赖氨酸的组合消除了XopO介导的HR,这表明AvrRps4家族成员对莴苣的感知有不同的结构要求。一起,我们的结果为AvrRps4及其同源物的加工和识别提供了见解。
During pathogenesis, effector proteins are secreted from the pathogen to the host plant to provide virulence activity for invasion of the host. However, once the host plant recognizes one of the delivered effectors, effector-triggered immunity activates a robust immune and hypersensitive response (HR). In planta, the effector
AvrRps4 is processed into the N-terminus (AvrRps4N ) and the C-terminus (AvrRps4C ). AvrRps4C is sufficient to trigger HR in turnip and activate AtRRS1/AtRPS4-mediated immunity in Arabidopsis; on the other hand, AvrRps4N induces HR in lettuce. Furthermore, AvrRps4N -mediated HR requires a conserved arginine at position 112 (R112), which is also important for full-length AvrRps4 (AvrRps4F ) processing. Here, we show that effector processing and effector recognition in lettuce are uncoupled for the
AvrRps4 family. In addition, we compared effector recognition by lettuce of
AvrRps4 and its homologues, HopK1 and XopO. Interestingly, unlike for AvrRps4 and HopK1, mutation of the conserved R111 in XopO by itself was insufficient to abolish recognition. The combination of amino acid substitutions arginine 111 to leucine with glutamate 114 to lysine abolished the XopO-mediated HR, suggesting that
AvrRps4 family members have distinct structural requirements for perception by lettuce. Together, our results provide an insight into the processing and recognition of
AvrRps4 and its homologues.