Transcriptional coactivator; part of the gene cluster that mediates the biosynthesis of cladofulvin, a conidial pigment not required for virulence but that plays a role in fitness and resistance to environmental stresses including UV light and low-temperature stress. With claE, coregulates the production of cladofulvin. Expression is positively regulated by the transcriptional regulator wor1 (PubMed:24521437). Expression is down-regulated during biotrophic growth within tomato leaves (PubMed:27997759). The expression is induced at later stages of infection when conidiophores emerge from the plant and produce conidia (PubMed:24465762).