Current understanding and perspectives on the potential mechanisms of immune priming in beetles

Beetles are the most diverse group of insects in Insecta which can be found in almost every habitat and environment on Earth. The possessing of the rapid and effective immune defenses is one of the important factors for their success. It is generally recognized that beetles only rely on the non-specific innate immune defense, without immunological memory, to fight against pathogens. However, there was cumulative evidence for the innate immune memory in invertebrates, including beetles, over the last decades, implying that insect innate immunity is more complex and has more features than previously thought. In beetles, it has been well documented that the specific or nonspecific enhanced immunocompetence can persist throughout development within generations and can even be transferred to the descendents in the next generation. Although insect immune priming might be shaped by epigenetic modifications and transferring effectors, mRNA and microbial signals, the solid experimental evidence to support the causal relationship between any of them and immune priming is still scarce. The combined usage of 'omics' approaches and CRISPR/Cas9 in the appropriate insect models with well-known genetic background, Tribolium castaneum and Tenebrio molitor, will help us to decipher the molecular mechanisms by which immune priming occurs in beetles in depth.