Beyond bitter: plant triterpenoids in the battle against herbivorous insects

Triterpenes are pivotal components of plant defence, offering a sustainable alternative to synthetic pesticides in insect pest management. They serve as critical components of both direct and indirect defence strategies, impacting various facets of herbivore behaviour and development. These structurally diverse metabolites not only deter herbivores directly but also modulate ecological interactions, potentially contributing to plant immunity. Despite their ecological and evolutionary significance, a comprehensive understanding of triterpene utility in plant defence, specifically towards herbivorous insects remains patchy. This review explores the evolutionary arms race between plants and insect herbivores, focusing on how pests evolved counter strategies against triterpene-based defences and the implications for long-term resistance management. However, their effective deployment requires a comprehensive framework that integrates evolutionary biology, ecological dynamics, and biotechnological interventions. Advancements in genome editing, metabolic engineering, and RNA interference (RNAi) provide promising avenues to optimize triterpene production in crops while targeting insect defence pathways. By integrating molecular, ecological, and biotechnological insights, this review proposes a conceptual framework to harness triterpenes for sustainable agriculture, reducing pesticide dependency while maintaining ecological balance. Addressing key knowledge gaps through interdisciplinary research will be critical for translating these discoveries into scalable agricultural solutions, ensuring crop resilience and long-term food security.