Crosstalk in the cold: host-microbe interactions in insect diapause.

Despite the overwhelming diversity and ecological impact of insects across most ecosystems, their responses to environmental stress remain underexplored. To survive temperate seasonal stressors, particularly winter cold conditions and nutrient and water shortage, insects undergo physiological changes and overwinter in a diapause state. During diapause, cessation of development is coupled with reduced metabolic activity, analogous to hibernation in mammals, in which gut microbiota help manage waste and recycle nitrogen. Similarly, many insects have obligate symbiotic relationships with microbes that support nutrient acquisition. However, unlike mammals, many insects have open or transient gut communities, making it more likely that microbial dynamics are strongly shaped by environmental microbes acquired through food or habitat. This review synthesizes recent literature on the roles of host-associated microbial communities in insect diapause, spanning nutrient provisioning, nitrogen recycling, and host immunity, including how associated microbes contribute to pathogen defense during dormancy. We propose future research avenues for more mechanistic understanding of host-microbe interactions involved in diapause, drawing on conceptual parallels established from mammalian hibernation research.