Pathogenic exonic circRNA from Cochliobolus heterostrophus interacts with host miRNA to suppress maize defense1

Circular RNAs (circRNAs) are a group of widely discovered non-coding RNAs in different organisms, but their biological function is largely unknown, especially in plant-microbial interaction. In this study, we identified an exonic circRNA (Che-circR2410) from the fungus Cochliobolus heterostrophus ( C. heterostrophus ) that, together with its corresponding linear RNA ChCYP51 , synergistically regulates the virulence of C . heterostrophus to maize. Further in - situ hybridization and the dual-luciferase reporter assays reveal the interaction between pathogenic circRNA Che-circR2410 and its cross-kingdom host target, zma-miR399e-5p. Additionally, lesion areas caused by both the wild-type C. heterostrophus and the circR2410 knock-out strain (∆ ChcircR2410 ) showed no significant difference on maize miR399e silencing mutant, providing support for the interaction between Che-circR2410 and zma-miR399e-5p. Moreover, we found that zma-miR399e affects the expression of autophagy-related genes, regulating maize immunity. Thus, our findings reveal a cross-kingdom interaction between the pathogenic exonic circRNA and host miRNA, modulating C. heterostrophus infection in maize. This study broadens our understanding of the C. heterostrophus -maize interaction at the level of non-coding RNA.