The CID1 cyclin C-like gene is important for plant infection in Fusarium graminearum

Head blight or scab caused by Fusarium graminearum is a destructive disease of wheat and barley. The pathogen can cause severe yield losses and contaminates infested kernels with harmful mycotoxins. In this study, we characterized the CID1 gene in F. graminearum that is an ortholog of the Fusarium verticilloidesFCC1 and yeast UME3 genes. The protein encoded by CID1 has typical structural features of C-type cyclins. Deletion of CID1 resulted in a reduction in conidiation and vegetative growth but an increase in pigmentation. The Δcid1 mutant was female sterile but could outcross as a male. It was significantly reduced in DON production and virulence on wheat heads and corn stalks. Only about 50% of inoculated spikelets developed scab symptoms and scab disease rarely extended to nearby florets, suggesting that the Δcid1 mutant was defective in colonizing and spreading in wheat heads. Deletion of CID1 resulted in reduced expression levels of TRI5 and TRI101 but increased PKS12 expression. When expressed in F. verticillioides, the CID1 gene complemented the defects of the Δfcc1 mutant in conidiation, hyphal growth, and fumonisin production. Our data indicate that the CID1 C-type cyclin gene plays multiple roles in the regulation of vegetative growth, sexual development, conidiation, DON production, and pathogenicity.