Hypha-specific G1 cyclin-related protein involved in regulation of morphogenesis and opaque cells filamentous growth, and required for both conventional and pheromone-stimulated biofilm formation. Required to maintain hyphal tip localization of actin and SPA2. Regulates the CDC28 kinase during hyphal growth. The CDC28-HGC1 complex phosphorylates and prevents RGA2 from localizing to hyphal tips, leading to localized CDC42 activation for hyphal extension. The CDC28-HGC1 complex also phosphorylates SEC2 and maintains CDC11 phosphorylation throughout hyphal growth. Moreover CDC28-HGC1 phosphorylation of EFG1 represses cell separation genes during hyphal growth. Also partially controls SEP7 phosphorylation status and subsequent septin ring dynamics. Required for virulence and especially mediates dynamic adhesion to endothelium of blood vessels during circulation. Interacts with CDC28. Transcript is detected only in the apical cells of hyphae, suggesting that HGC1 is transcribed in the apical cell. Induced during hyphal formation and upon exposure to host serum. Expression is regulated by the cAMP/PKA pathway, EFG1, FLO8, SSN6, RAD52, TUP1, and UME6. Repressed by farnesol and linalool. Belongs to the cyclin family.