Intron turnover is essential to the development and pathogenicity of the plant pathogenic fungus Fusarium graminearum

Intron lariats excised during the splicing process are rapidly degraded by RNA lariat debranching enzyme (Dbr1) and several exonucleases. Rapid turnover of lariat RNA is essential to cellular RNA homeostasis. However, the functions of Dbr1 have not been investigated in filamentous fungi. Here, we characterized the molecular functions of Dbr1 in Fusarium graminearum, a major fungal plant pathogen. Deletion of FgDBR1 resulted in pleiotropic defects in hyphal growth, conidiation, sexual reproduction, and virulence. Through transcriptome analysis, we revealed that the deletion mutant exhibited global accumulation of intron lariats and upregulation of ribosome-related genes. Excessive accumulation of lariat RNA led to reduced overall protein synthesis, causing various phenotypic defects in the absence of FgDBR1. The results of this study demonstrate that a compromised intron turnover process affects development and pathogenesis in this fungus and that Dbr1 function is critical to plant pathogenic fungi.