The secret life of insect-associated microbes and how they shape insect-plant interactions

Insects are associated with a plethora of different microbes of which we are only starting to understand their role in shaping insect-plant interactions. Besides directly benefitting from symbiotic microbial metabolism, insects obtain and transmit microbes within their environment, making them ideal vectors and potential beneficiaries of plant diseases and microbes that alter plant defenses. To prevent damage, plants elicit stress-specific defenses to ward off insects and their microbiota. However, both insects and microbes harbor a wealth of adaptations that allow them to circumvent effective plant defense activation. In the past decades, it has become apparent that the enormous diversity and metabolic potential of insect-associated microbes may play a far more important role in shaping insect-plant interactions than previously anticipated. The latter may have implications for the development of sustainable pest control strategies. Therefore, this review sheds light on the current knowledge on multitrophic insect-microbe-plant interactions in a rapidly expanding field of research.