Despite the pivotal role of jasmonic acid in the outcome of plant-microorganism interactions, JA-signaling components in roots of perennial trees like western balsam poplar (Populus trichocarpa) are poorly characterized. Here we decipher the poplar-root JA-perception complex centered on PtJAZ6, a co-repressor of JA-signaling targeted by the effector protein MiSSP7 from the ectomycorrhizal basidiomycete Laccaria bicolor during symbiotic development. Through protein–protein interaction studies in yeast we determined the poplar root proteins interacting with PtJAZ6. Moreover, we assessed via yeast triple-hybrid how the mutualistic effector MiSSP7 reshapes the association between PtJAZ6 and its partner proteins. In the absence of the symbiotic effector, PtJAZ6 interacts with the transcription factors PtMYC2s and PtJAM1.1. In addition, PtJAZ6 interacts with it-self and with other Populus JAZ proteins. Finally, MiSSP7 strengthens the binding of PtJAZ6 to PtMYC2.1 and antagonizes PtJAZ6 homo-/heterodimerization. We conclude that a symbiotic effector secreted by a mutualistic fungus may promote the symbiotic interaction through altered dynamics of a JA-signaling-associated protein–protein interaction network, maintaining the repression of PtMYC2.1-regulated genes.

尽管茉莉酸在植物-微生物相互作用的结果中发挥着关键作用，但像西部香脂杨 ( Populus trichocarpa )等多年生树木根部的 JA 信号成分的特征却很少。在这里，我们破译了以 PtJAZ6 为中心的杨根 JA 感知复合物，PtJAZ6 是共生发育过程中外生担子菌Laccaria bicolor的效应蛋白 MiSSP7 靶向的 JA 信号传导的共阻遏物。通过酵母中蛋白质-蛋白质相互作用研究，我们确定了杨树根蛋白质与 PtJAZ6 的相互作用。此外，我们通过酵母三重杂交评估了互惠效应子 MiSSP7 如何重塑 PtJAZ6 及其伙伴蛋白之间的关联。在缺乏共生效应子的情况下，PtJAZ6 与转录因子 PtMYC2s 和 PtJAM1.1 相互作用。此外，PtJAZ6 与其自身以及其他杨树JAZ 蛋白相互作用。最后，MiSSP7 增强了 PtJAZ6 与 PtMYC2.1 的结合并拮抗 PtJAZ6 同源/异源二聚化。我们得出的结论是，共生真菌分泌的共生效应子可能通过改变 JA 信号相关蛋白-蛋白相互作用网络的动力学来促进共生相互作用，从而维持对 PtMYC2.1 调节基因的抑制。