The ascomycete Aspergillus nidulans is a model organism to study fungal development. Conidiation is controlled by the product of the brlA gene. Many gene products act upstream of brlA, probably allowing the synthesis of chemicals or allowing the transduction of environmental signals to trigger brlA transcription. The A. nidulans genome contains genes for a phytochrome (fphA), two homologs of N.crassa WC-1 and WC-2 (lreA and lreB) and a veA gene. Red and blue light stimulate conidiation in A. nidulans, but mutations in the veA gene allow conidiation in the dark. Recently, it has been shown that the phytocrome FphA interacts with VeA and LreA and LreB. However, the mechanism that the photoreceptors employ to activate conidiation remains unknown. We have found that the expression of several conidiation genes, including brlA, fluG flbA, flbB and flbC, was regulated by light. The photoactivation of these genes showed a quick reponse with mRNA accumulation increasing after 5 minutes of illumination. brlA mRNA accumulation after illumination increased with time showing maximum values between 30 to 60 minutes and revealed a two-component activation. Deletion of the photoreceptor genes fphA, lreA and lreB reduced the activation by light of the studied genes. None of these genes are essential for gene photoactivation since we observed light-dependent mRNA accumulation in strains with single deletion of photoreceptor genes. On-going experiments provides a model for the light-dependent activation of conidiation.