CgrBrlA, CgrAbaA, and CgrWetA form a developmental regulatory cascade controlling conidiation, spore integrity, and virulence in Colletotrichum graminicola.

Colletotrichum graminicola, the causal agent of maize anthracnose, relies on asexual spores for disease initiation and spread, yet the transcriptional mechanisms controlling conidiation and infection-related development remain incompletely understood. Here, we functionally characterize three putative homologs of the conserved fungal developmental regulators BrlA, AbaA, and WetA in C. graminicola. Targeted deletion analyses showed that CgrbrlA is essential for conidiophore formation and conidium production, while CgrabaA is required for proper conidiophore differentiation and normal sporulation. In contrast, deletion of CgrwetA did not abolish conidiation but caused severe defects in conidial morphology, structural integrity, germination, appressorium formation, and virulence on maize leaves. Yeast one-hybrid and EMSA assays demonstrated that CgrBrlA binds to the promoter regions of both CgrbrlA and CgrabaA, supporting an autoregulatory circuit and direct regulation of the downstream developmental regulator CgrabaA. Integrated transcriptomic and proteomic analyses further revealed both shared and stage-specific regulatory outputs of the cascade. CgrBrlA was associated primarily with transcriptional and metabolic reprogramming during conidiation initiation, CgrAbaA with redox homeostasis and signaling, and CgrWetA with membrane organization, lipid metabolism, energy metabolism, and spore maturation. Together, these findings support the presence of a BrlA-AbaA-WetA-like regulatory cascade coordinating conidiation, conidial fitness, and pathogenicity in C. graminicola.