Plants interact with microorganisms in the environment during all stages of their development and in most of their organs. These interactions can be either beneficial or detrimental for the plant and may be transient or long-term. In extreme cases, microorganisms become endoparastic or endophytic and permanently reside within a plant, while the host plant undergoes developmental reprogramming and produces new tissues or organs as a response to the invasion. Events at the cellular and molecular level following infection have been extensively described, however the mechanisms of how these microorganisms locate their plant hosts via chemotaxis remain largely unknown. In this review, we summarize recent findings concerning the signalling molecules that regulate chemotaxis of endoparasitic/endophytic bacteria, fungi, and nematodes. In particular, we will focus on the molecules secreted by plants that are most likely to act as guidance cues for microorganisms. These compounds are found in a wide range of plant species and show a variety of secondary effects. Interestingly, these compounds show different attraction potencies depending on the species of the invading organism, suggesting that cues perceived in the soil may be more complex than anticipated. However, what the cognate receptors are for these attractants, as well as the mechanism of how these attractants influence these organisms, remain important outstanding questions. Host-targeting marks the first step of plant—microorganism interactions, therefore understanding the signalling molecules involved in this step plays a key role in understanding these interactions as a whole.

植物在其发育的各个阶段以及其大部分器官中都与环境中的微生物相互作用。这些相互作用对植物可能是有益的，也可能是有害的，并且可能是短暂的或长期的。在极端情况下，微生物变成内寄生或内生并永久驻留在植物内，而宿主植物则经历发育重编程并产生新的组织或器官作为对入侵的反应。感染后细胞和分子水平的事件已被广泛描述，然而这些微生物如何定位其植物宿主的机制通过趋化性仍然很大程度上未知。在这篇综述中，我们总结了有关调节内寄生/内生细菌、真菌和线虫趋化性的信号分子的最新发现。特别是，我们将重点关注植物分泌的最有可能充当微生物指导线索的分子。这些化合物存在于多种植物物种中，并表现出多种副作用。有趣的是，这些化合物根据入侵生物的种类而表现出不同的吸引力，这表明在土壤中感知到的线索可能比预期的更复杂。然而，这些引诱剂的同源受体是什么，以及这些引诱剂如何影响这些生物体的机制，仍然是重要的悬而未决的问题。宿主靶向标志着植物与微生物相互作用的第一步，因此了解该步骤中涉及的信号分子对于理解这些相互作用的整体起着关键作用。