Multifaceted roles of ethylene in plants: From traditional functions to modern insights into tritrophic interactions for sustainable agriculture

Ethylene, a critical phytohormone, regulates diverse physiological processes in plants, from growth and development to responses to abiotic and biotic stresses. While its role in plant development and direct defence against herbivory has been extensively studied, its potential involvement in indirect defence, particularly in recruiting biological control agents, remains insufficiently explored. This review examines ethylene's multifaceted role in plants, with an emphasis on its established functions in plant defence and the need for further research into its contribution to indirect defences. Beginning with an overview of ethylene biosynthesis, transport, and signaling pathways, we outline its traditional roles in plant growth and development before discussing its functions in plant defence. The review explores ethylene's involvement in direct defences through physical and biochemical responses and its interactions with other phytohormones. Additionally, we highlight the limited studies on ethylene's potential role in indirect defences, particularly in plant-plant communication and the recruitment of natural enemies such as predators and parasitoids, underscoring the need for further investigation in this area. Furthermore, we discuss the potential applications of ethylene in sustainable agriculture, proposing its integration into pest management strategies to enhance crop resilience and reduce reliance on synthetic pesticides. By identifying key knowledge gaps, this review highlights the importance of ethylene as a promising but underexplored component of plant defence and calls for future research to better understand its ecological significance and practical applications in pest management.