Recently, identification and functional studies of circular RNAs, a type of non-coding RNAs arising from a ligation of 3′ and 5′ ends of a linear RNA molecule, were conducted in mammalian cells with the development of RNA-seq technology.
Compared with animals, studies on circular RNAs in plants are less thorough. Researchers from the University of Nebraska conducted a genome-wide identification of circular RNA candidates in Arabidopsis with their own developed bioinformatics tool in several existing RNA-seq datasets specifically for non-coding RNAs.
A total of 164 circular RNA candidates were identified from RNA-seq data, and 4 circular RNA transcripts, including both exonic and intronic circular RNAs, were experimentally validated. Interestingly, these results show that circular RNA transcripts are enriched in the photosynthesis system for the leaf tissue and correlated to the higher expression levels of their parent genes. Sixteen out of all 40 genes that have circular RNA candidates are related to the photosynthesis system, and out of the total 146 exonic circular RNA candidates, 63 are found in chloroplast.