With the development of high-throughput sequencing technology, circular RNAs (circRNAs) have gradually become a hotspot in the research on non-coding RNA. CircRNAs are produced by the covalent circularization of a downstream 3' splice donor and an upstream 5' splice acceptor through backsplicing, and they are pervasive in eukaryotic cells. CircRNAs used to be considered byproducts of false splicing, whereas an explosion of related studies in recent years has disproved this misconception. Compared with the rich studies of circRNAs in animals, the study of circRNAs in plants is still in its infancy. In this review, we introduced the discovery of plant circRNAs, the discovery of plant circRNAs, the circularization feature, expression specificity, conservation, and stability of plant circRNAs and expounded the identification tools, main types, and biogenesis mechanisms of circRNAs. Furthermore, we summarized the potential roles of plant circRNAs as microRNA (miRNA) sponges and translation templates and in response to biotic/abiotic stress, and briefed the degradation and localization of plant circRNAs. Finally, we discussed the challenges and proposed the future directions in the research on plant circRNAs.
Keywords: backsplicing; biogenesis mechanism; circular RNAs; miRNA sponge.