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

Circular RNAs (circRNAs) are a group of widely discovered non-coding RNAs in different organisms, but their biological functions are largely unknown, especially in plant–microbial interactions. In this study, we identified an exonic circRNA (Che-circR2410) from the fungus Cochliobolus heterostrophus that, together with its corresponding linear RNA ChCYP51, synergistically regulates the virulence of C. heterostrophus to maize. Further in situ hybridization and dual-luciferase reporter assays revealed 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 (ΔChcircR2410) showed no significant difference on the 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.