Abiotic stress-induced circular RNAs: Implications for plant stress tolerance

Abiotic stress such as drought, salinity, extreme temperatures, and nutrient imbalances significantly reduce crop yields worldwide. Plants respond to these challenges through complex regulatory networks involving non-coding RNAs, among which circular RNAs (circRNAs) have recently gained attention as crucial modulators of stress adaptation. CircRNAs are stable, covalently closed-loop transcripts generated by back-splicing, exhibiting tissue-specific expression patterns. Advances in sequencing technologies have identified circRNAs across numerous plant species, revealing their roles in development and abiotic stress responses. Functionally, circRNAs act as competing endogenous RNAs by sponging microRNAs, thereby regulating downstream gene expression. CircRNAs miRNA-sponging are well established in animals but remain limited in plants. Experimental studies demonstrate circRNA-miRNA-mRNA networks are associated with plant responses tolerance to drought, salinity, temperature extremes, metal toxicity, and nutrient stress through mechanisms such as antioxidant activity, ion homeostasis, and hormone signaling. Furthermore, engineered circRNAs hold promise for crop improvement via synthetic biology approaches. This review highlights current insights into circRNA biogenesis, detection, and function in plants, emphasizing their potential to advance RNA-based strategies for developing stress-resilient crops, while framing engineered circRNAs as a promising yet still speculative future direction.