Serendipita indica is an axenically cultivable fungus, which colonizes a broad range of plant species including the model plant Arabidopsis thaliana. Root colonization by this endophyte leads to enhanced plant fitness and performance and promotes resistance against different biotic and abiotic stresses. The involvement of MPK6 in this mutualistic interaction had been previously shown with an mpk6 A. thaliana mutant, which failed to respond to S. indica colonization. Here, we demonstrate that mpk6 roots are significantly less colonized by S. indica compared to wild-type roots and the foliar application of plant hormones, ethylene, or jasmonic acid, restores the colonization rate at least to the wild-type level. Further, hormone-treated mpk6 plants show typical S. indica-induced growth promotion effects. Moreover, expression levels of several genes related to plant defense and hormone signaling are significantly changed at different colonization phases. Our results demonstrate that the successful root colonization by S. indica depends on efficient suppression of plant immune responses. In A. thaliana, this process relies on intact hormone signaling in which MPK6 seems to play a pivotal role.

中文翻译：

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MPK6 作为乙烯/茉莉酸信号传导介质在籼稻定植拟南芥根中的作用

Serendipita indica 是一种可无菌培养的真菌，它定植于多种植物物种，包括模式植物拟南芥。这种内生菌的根系定植可增强植物的适应性和性能，并促进对不同生物和非生物胁迫的抗性。MPK6 在这种互惠互作中的参与先前已与 mpk6 A. thaliana 突变体一起显示，该突变体未能对 S. indica 殖民化做出反应。在这里，我们证明了与野生型根相比，mpk6 根被 S. indica 的殖民显着减少，并且叶面施用植物激素、乙烯或茉莉酸，至少将殖民率恢复到野生型水平。此外，激素处理的 mpk6 植物表现出典型的籼稻诱导的生长促进作用。而且，与植物防御和激素信号相关的几个基因的表达水平在不同的定植阶段发生了显着变化。我们的结果表明，籼稻成功根系定植取决于对植物免疫反应的有效抑制。在拟南芥中，这个过程依赖于完整的激素信号，其中 MPK6 似乎起着关键作用。