The science of insect-yeast symbiosis and its impact on plant interactions

Abstract

Herbivorous insects present significant challenges to agriculture, often aided by their associated microbial communities which help them overcome plant defenses. Yeasts, commonly found as environmental associates or endosymbionts of insects, remain less studied compared to bacteria. This literature review synthesizes current research and evaluates key hypotheses regarding the mutualistic relationship between insects and yeasts, as well as their impact on plants. Yeasts provide nutritional benefits, such as protein for fruit fly development and carbohydrate digestion for bark beetles, by producing carbohydrate-active enzymes. In bark beetles, endosymbiotic yeasts also detoxify plant defense compounds like pinene, salicin, and naringenin. Yeasts gain dispersal advantages through insect-mediated transport between nutrient-rich substrates and often depend on ingestion for reproduction. Volatile organic compounds (VOCs) produced by yeasts play a critical role in insect attraction and communication, with certain key VOCs being conserved across yeast species. Yeast volatiles influence behaviors such as aggregation in bark beetles and demonstrate their ecological importance. Yeasts can also modulate plant responses, with some activating or suppressing plant defenses, while others emit VOCs that inhibit phytopathogenic fungi. Despite these findings, further research is needed to fully understand the mechanisms underlying these interactions. The relationship between insects and yeasts varies across species, but yeasts significantly influence insect ability to exploit plant resources. Studying these interactions offers valuable insights for developing improved pest management strategies in agriculture.