From hosts to parasites: hormones driving symbiosis-induced de novo organogenesis.

Abstract

Plants have evolved diverse adaptations in signal perception, hormone regulation, and organ development that enable the formation of specialised structures such as nematode-induced galls, rhizobia-induced nodules, and host-induced parasitic plant haustoria that facilitate both parasitic and mutualistic symbiosis. Despite their differences, these organs share common gene regulatory mechanisms with lateral root development. By comparing their mechanisms of hormonal regulation, we illuminate the shared genetic underpinnings and how plants repurpose vegetative development pathways in response to biotic stimuli. This adaptive retooling positions plants along the symbiotic spectrum from exploited hosts to mutualistic partners and strategic predators. Comparative analysis of the hormonal mechanisms that drive symbiotic organogenesis highlights the plasticity of developmental processes and the interplay between internal signalling and external environmental cues.