A large-scale circular RNA profiling reveals universal molecular mechanisms responsive to drought stress in maize and Arabidopsis

Drought is a major abiotic stress that threatens global food security. Circular RNAs (circRNAs) are endogenous RNAs. How these molecules influence plant stress responses remains elusive. Here, a large scale circRNA profiling identified 2174 and 1354 high-confidence circRNAs in maize and Arabidopsis, respectively, and most were differentially expressed in response to drought. A substantial number of drought-associated circRNA hosting genes were involved in conserved or species-specific pathways in drought responses. Comparative analysis revealed that circRNA biogenesis was more complex in maize than in Arabidopsis. In most cases, maize circRNAs were negatively correlated with sRNA accumulation. In 368 maize inbred lines, the circRNA-hosting genes were enriched for SNPs associated with circRNA expression and drought tolerance, implying either important roles of circRNAs in maize drought responses or their potential use as biomarkers for breeding drought-tolerant maize. Additionally, the expression levels of circRNAs derived from drought-responsible genes encoding calcium-dependent protein kinase and cytokinin oxidase/dehydrogenase were significantly associated with drought tolerance of maize seedlings. Specifically, Arabidopsis plants overexpressing circGORK (Guard cell outward-rectifying K+-channel) were hypersensitive to ABA, but insensitive to drought, suggesting a positive role of circGORK in drought tolerance. We report the transcriptomic profiling and transgenic studies of circRNAs in plant drought responses, and provide evidences highlighting the universal molecular mechanisms involved in plant drought tolerance. Overall design: RNA-seq and CircRNA-seq (RNaseR+) to Arabidopsis and maize plants under well-watered condition (WW) and drought treatments at various levels (DT2,DT3,DT4 and DT5 for Arabidopsis; DT2, DT3 and DT4 for Maize). Each treatment has 2 biological replicates

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Zhang P, Fan Y, Sun X, Chen L, Terzaghi W, Bucher E, Li L, Dai M