Phycomyces MADB interacts with MADA to form the primary photoreceptor complex for fungal phototropism

The fungus Phycomyces blakesleeanus reacts to environmental signals, including light, gravity, touch, and the presence of nearby objects, by changing the speed and direction of growth of its fruiting body (sporangiophore). Phototropism, growth toward light, shares many features in fungi and plants b...

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Bibliographic Details
Published in:	Proceedings of the National Academy of Sciences - PNAS 2009-04, Vol.106 (17), p.7095-7100
Main Authors:	Sanz, Catalina, Rodríguez-Romero, Julio, Idnurm, Alexander, Christie, John M, Heitman, Joseph, Corrochano, Luis M, Eslava, Arturo P
Format:	Article
Language:	eng
Subjects:	Alternative Splicing - genetics Base Sequence Biochemistry Biological Sciences blue light blue light photoreceptor Color Complementary DNA DNA-Binding Proteins - genetics DNA-Binding Proteins - metabolism Escherichia coli Fruit bodies Fungal Proteins - genetics Fungal Proteins - metabolism Fungi gene expression regulation Genes Genetic mutation Genome, Fungal - genetics Genomes Genomics Gravity Light Light effects Light intensity madB gene Messenger RNA microbial genetics Molecular modelling Molecular Sequence Data Mutants Mutation Mutation - genetics Neurospora Perception Photoreceptor Cells - metabolism Photoreceptors Phototropism Phycomyces Phycomyces - genetics Phycomyces - metabolism Phycomyces blakesleeanus Phylogeny Physical growth protein-protein interactions Proteins Sequence Alignment Sporangiophores Tactile stimuli transcription (genetics) Transcription factors Transcription Factors - genetics Transcription Factors - metabolism Transcription, Genetic - genetics Yeasts Zinc finger proteins
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Summary:	The fungus Phycomyces blakesleeanus reacts to environmental signals, including light, gravity, touch, and the presence of nearby objects, by changing the speed and direction of growth of its fruiting body (sporangiophore). Phototropism, growth toward light, shares many features in fungi and plants but the molecular mechanisms remain to be fully elucidated. Phycomyces mutants with altered phototropism were isolated [almost equal to]40 years ago and found to have mutations in the mad genes. All of the responses to light in Phycomyces require the products of the madA and madB genes. We showed that madA encodes a protein similar to the Neurospora blue-light photoreceptor, zinc-finger protein WC-1. We show here that madB encodes a protein similar to the Neurospora zinc-finger protein WC-2. MADA and MADB interact to form a complex in yeast 2-hybrid assays and when coexpressed in E. coli, providing evidence that phototropism and other responses to light are mediated by a photoresponsive transcription factor complex. The Phycomyces genome contains 3 genes similar to wc-1, and 4 genes similar to wc-2, many of which are regulated by light in a madA or madB dependent manner. We did not detect any interactions between additional WC proteins in yeast 2-hybrid assays, which suggest that MADA and MADB form the major photoreceptor complex in PHYCOMYCES: However, the presence of multiple wc genes in Phycomyces may enable perception across a broad range of light intensities, and may provide specialized photoreceptors for distinct photoresponses.
ISSN:	0027-8424 1091-6490