Alkaloids as mediators in plant-microbe interactions: Metabolism and role in the rhizosphere

Abstract

Alkaloids represent one of the largest classes of plant specialized metabolites, characterized by diverse chemical structures and activities. Known for their bioactive properties, these metabolites have primarily been described in the context of aboveground defense against pathogens, insects, and herbivores. Beyond these defensive functions, recent studies have revealed that alkaloids also mediate interactions between plants and their associated root microbiota. These interkingdom metabolic interactions improves plant fitness, particularly under changing environmental conditions. This review highlights the metabolism and roles of alkaloids in the rhizosphere, a critical hotspot for interactions between plants and soil microbes. We also explore key questions that expand our understanding of the role of plant specialized metabolites, extending beyond alkaloids, in plant-microbiota interactions and their broader implications for plant fitness.