The Potential Biological Roles of Circular RNAs in the Immune Systems of Insects to Pathogen Invasion

Abstract

Circular RNAs (circRNAs) are a newly discovered class of endogenously expressed non-coding RNAs (ncRNAs). They are highly stable, covalently closed molecules that frequently exhibit tissue-specific expression in eukaryotes. A small number of circRNAs are abundant and have been remarkably conserved throughout evolution. Numerous circRNAs are known to play important biological roles by acting as microRNAs (miRNAs) or protein inhibitors (‘sponges’), by regulating the function of proteins, or by being translated themselves. CircRNAs have distinct cellular functions due to structural and production differences from mRNAs. Recent advances highlight the importance of characterizing circRNAs and their targets in a variety of insect species in order to fully understand how they contribute to the immune responses of these insects. Here, we focus on the recent advances in our understanding of the biogenesis of circRNAs, regulation of their abundance, and biological roles, such as serving as templates for translation and in the regulation of signaling pathways. We also discuss the emerging roles of circRNAs in regulating immune responses to various microbial pathogens. Furthermore, we describe the functions of circRNAs encoded by microbial pathogens that play in their hosts.

Multi-omics study and ncRNA regulation of anti-BmNPV in silkworms, Bombyx mori: an update

“…CircRNA was first identified by using electron microscopy in 1976 but did not attract much attention then. Only in recent years, with the development of the high-throughput sequencing technique and the discovery of a series of circRNAs, researchers have gradually realized the specificity of circRNA and its functional importance in vivo ( Sanger et al, 1976 ; Jeck et al, 2013 ; Memczak et al, 2013 ; Abbas et al, 2023 ). With the development of technology, the functions of circRNA have been found not only to act as a miRNA sponge that regulates the transcriptional level but also to encode proteins and regulate protein binding at different levels ( Qu et al, 2015 ; Kristensen et al, 2019 ).…”

Novel Insights into the circRNA-Modulated Developmental Mechanism of Western Honey Bee Larval Guts

“…It has been suggested that circRNAs are crucial regulators in immune defense of insects against pathogens or parasites [60]. Hu et al [61] investigated the circRNA expression in the gut tissue of Bombyx mori following BmNPV challenge, and the results showed that circRNAs potentially regulate the genes annotated to ubiquitin, apoptosis, and endocytosis signaling pathways by the ceRNA axis.…”

Non-coding RNAs in Lepidoptera

“…Circular RNAs play roles in gene expression by modulating transcription in the nucleus and regulating translation in the cytoplasm. In the nucleus, circRNAs play a diverse biological role including chromatin looping, transcription regulation, and alternative splicing [170][171][172][173][174]. Circular RNAs can form three-stranded structures harboring a DNA:RNA hybrid named R-loops with their producing locus to impact transcription [171].…”