The Role of the Mediator Complex in Modulating CjXDR1-Induced Multidrug Resistance and Virulence in Clarireedia jacksonii.

The Mediator complex is a central regulator of gene expression in pathogenic fungi; however, its composition and functions remain uncharacterized in Clarireedia jacksonii, a major fungal pathogen in turfgrass. In this study, we systematically analyzed the Mediator complex in C. jacksonii and identified its key role in transcriptional activation. Functional characterization of 10 knockout mutants revealed distinct roles for Mediator subunits in cell growth, fungicide resistance, pathogenicity, and stress responses. Notably, Med1, Med31, Med15, and Cdk8 were essential for pathogenicity, and subunits from Tail and Kinase modules were closely associated with fungicide resistance and exhibited altered expression upon CjXDR1 deletion. Deletion of Med5 increased sensitivity to propiconazole, whereas deletion of Cdk8 and CycC conferred fungicide resistance. Further analyses demonstrated that disruption of the Mediator complex altered the expression of CjXDR1-induced downstream targets and impacted sterol biosynthesis. Together, these findings provide the first comprehensive insight into the Mediator complex in C. jacksonii, highlighting its critical role in multidrug resistance and its potential as a target for antifungal strategies.