The Aspergillus nidulans Phytochrome FphA Represses Sexual Development in Red Light

Abstract

Phytochrome photoreceptors sense red and far-red light through photointerconversion between two stable conformations, a process mediated by a linear tetrapyrrole chromophore. Originally, phytochromes were thought to be confined to photosynthetic organisms including cyanobacteria, but they have been recently discovered in heterotrophic bacteria and fungi, where little is known about their functions. It was shown previously in the ascomycetous fungus Aspergillus nidulans that asexual sporulation is stimulated and sexual development repressed by red light. The effect was reminiscent of a phytochrome response, and indeed phytochrome-like proteins were detected in several fungal genomes. All fungal homologs are more similar to bacterial than plant phytochromes and have multifunctional domains where the phytochrome region and histidine kinase domain are combined in a single protein with a C-terminal response-regulator domain. Here, we show that the A. nidulans phytochrome FphA binds a biliverdin chromophore, acts as a red-light sensor, and represses sexual development under red-light conditions. FphA-GFP is cytoplasmic and excluded from the nuclei, suggesting that red-light photoperception occurs in the cytoplasm. This is the first phytochrome experimentally characterized outside the plant and bacterial kingdoms and the second type of fungal protein identified that functions in photoperception.

Light Represses Conidiation in Koji MoldAspergillus oryzae

“…7) FphA (Fungal phytochrome A) has been identified as a red light receptor in A. nidulans. 8) These successful studies of photoreaction in other filamentous fungi support the speculation that A. oryzae can also perceive various types of light with photoreceptors and show responses via light signal transduction pathways. Indeed, recent genome sequencing of A. oryzae indicates the existence of homologs of certain light-related genes in other filamentous fungi (Table 1).…”

“…6) Recently, in A. nidulans, a fungal phytochrome, FphA, was identified as a red light receptor that putatively binds to biliverdin chromophores. 8) In Aspergillis spp., it has been found that development is affected by light. A. flavus, A. parasiticus, and A. nidulans grown under light produce 5-to 10-fold more conidia than those grown under dark.…”

“…The fphA gene product serves as a photosensor and represses sexual development under red light. 8) veA is known to be a regulator gene of sexual and asexual development in A. nidulans. The veA gene regulates sexual development positively and simultaneously regulates asexual development negatively.…”

More Than a Repair Enzyme:Aspergillus nidulansPhotolyase-like CryA Is a Regulator of Sexual Development

“…This development is repressed by light, aeration, and in submerged culture, whereas it is promoted by the presence of a medium/air interface and the absence of light. To date, the fungal phytochrome FphA is the only analyzed developmental photosensor of A. nidulans (Blumenstein et al, 2005;Purschwitz et al, 2006).…”

“…This development is repressed by light, aeration, and in submerged culture, whereas it is promoted by the presence of a medium/air interface and the absence of light. To date, the fungal phytochrome FphA is the only analyzed developmental photosensor of A. nidulans (Blumenstein et al, 2005;Purschwitz et al, 2006).Inspection of the genome of the homothallic ascomycete A. nidulans (Galagan et al, 2005) revealed only a single putative CRY/photolyase-like gene, here termed cryA. The deduced protein of 567 amino acids includes a PHR domain that contains both DNA photolyase and FAD-binding domains.…”