Abstract
Plants engage in mutually beneficial relationships with microbes, such as arbuscular mycorrhizal fungi or nitrogen-fixing rhizobia, for optimized nutrient acquisition. In return, the microbial symbionts receive photosynthetic carbon from the plant. Both symbioses are regulated by the plant nutrient status, indicating the existence of signaling pathways that allow the host to fine-tune its interactions with the beneficial microbes depending on its nutrient requirements. Peptide hormones coordinate a plethora of developmental and physiological processes and, recently, various peptide families have gained special attention as systemic and local regulators of plant–microbe interactions and nutrient homeostasis. In this review, we identify five ‘rules’ or guiding principles that govern peptide function during symbiotic plant–microbe interactions, and highlight possible points of integration with nutrient acquisition pathways.
Plant interactions with arbuscular mycorrhizal fungi, beneficial soil bacteria, and nutrient homeostasis are optimized by an interconnected network of peptide signals.Symbiosis-regulating signaling peptides are members of large protein families, often with a variety of functions in plant physiology and development.The mechanism of peptide-signaling specificity in the context of plant–microbe interactions, nutrient homeostasis, and cross-kingdom peptide mimicry involves antagonism and coordination between individual peptide signals.Although many of the symbiosis-associated peptide signaling pathways converge at common downstream signaling hubs and intersect with phytohormone signaling, the signaling outcomes are, at least partially, unique.
