Epigenetics and non-coding RNAs in host-endosymbiont interactions: insights from Wolbachia and beyond

Symbioses are widespread in nature and are among major evolutionary forces. Insects have recurrently established intracellular symbioses with bacteria, balancing between immune responses and homeostasis. The processes involved in endosymbiosis establishment, maintenance, and control have recently been associated with epigenetic pathways and non-coding RNAs, which are known to regulate a wide range of cellular processes, including development, differentiation, immune response, and metabolism. Using the well-studied Wolbachia-Aedes aegypti model as a reference, we summarize how these mechanisms influence host gene expression, endosymbiont maintenance, and antiviral defence. Beyond Wolbachia, only a few examples have provided functional evidence of the role of epigenetics in regulating natural insect-bacteria associations. Collectively, these studies demonstrate that epigenetic factors can act as mediators of host-endosymbiont coordination; however, determining if such factors are drivers or by-products of symbiosis establishment will require further investigation.