Ménage à Trois: Unraveling the Mechanisms Regulating Plant–Microbe–Arthropod Interactions      

Gruden et al., 2020.

Plant‐microbe‐arthropod (PMA) interactions have important impacts on plant fitness, and recent studies shed light on how plants regulate responses in such complex interactions.

Biosynthetic pathways for the production of defensive and signaling compounds, and the corresponding signaling modules (mostly related to phytohormones) are key regulators both in interactions of the plant with either microbes or arthropods (two-way interactions), or when exposed to both (PMA; three-way interactions).

Most signaling modules regulating two-way interactions of plants with microbes or arthropods also operate in three-way PMA interactions, but changes in their speed or intensity (e.g., defense priming) and/or activation of additional pathways frequently occur.

These differences shape the outcome of PMA interactions and may have implications for ecologically based crop protection. 

 

Illustration of Multiway Interactions between Plants, Microbes, and Arthropods (PMA) and the Main Signaling Pathways Orchestrating the Corresponding Plant Responses. Plants must fine-tune their molecular responses to the interaction with a plethora of organisms with different lifestyles. Microbes and arthropods interact and can alter each other’s effects on plant health through their modulation of plant responses. Continuous arrows represent the two-way interactions between the plant and the microbe or the arthropod. Discontinuous arrows represent the three-way PMA interactions. Major signaling pathways coordinating plant responses during two-way and PMA interactions are represented, namely volatile organic compounds (VOCs), jasmonic acid (JA), salicylic acid (SA), abscisic acid (ABA), and ethylene signaling (ET). Major groups of arthropod and microbe lifestyles are illustrated by particular examples, microbes on the left side of the figure, arthropods on the right. The third trophic level (indirect interaction) is also represented by parasitoids and predators of arthropods. The insert represents arthropod-associated microbes impacting the arthropod interaction with the plant. Drawing by J. Lidoy, V. Lidoy, and J. Lidoy. Abbreviations: AM fungi, arbuscular mycorrhizal fungi; PGPF, plant growth-promoting fungi; PGPR, plant growth-promoting rhizobacteria.

 

https://doi.org/10.1016/j.tplants.2020.07.008

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