Endogenous egg immune defenses in the yellow mealworm beetle (Tenebrio molitor)

- Eggs of Tenebrio molitor induce multiple immune genes upon infection.
- The same immune genes are induced in adults and eggs of T. molitor.
- Transcript levels in eggs come close to those in adult beetles.
- Endogenous egg defenses are likely important for many insect species.

In order to survive microbe encounters, insects rely on both physical barriers as well as local and systemic immune responses. Most research focusses on adult or larval defenses however, whereas insect eggs are also in need of protection. Lately, the defense of eggs against microbes has received an increasing amount of attention, be it through endogenous egg defenses, trans-generational immune priming (TGIP) or parental investment. Here we studied the endogenous immune response in eggs and adults of Tenebrio molitor. We show that many immune genes are induced in both adults and eggs. Furthermore, we show that eggs reach comparable levels of immune gene expression as adults. These findings show that the eggs of Tenebrio are capable of an impressive endogenous immune response, and indicate that such inducible egg defenses are likely common in insects.

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