title: Distinct white collar-1 genes control specific light responses in Mucor circinelloides.
abstract: Light regulates many developmental and physiological processes in a large number of organisms. The best-known light response in the fungus Mucor circinelloides is the biosynthesis of beta-carotene. Here, we show that M. circinelloides sporangiophores also respond to light, exhibiting a positive phototropism. Analysis of both responses to different light wavelengths within the visible spectrum demonstrated that phototropism is induced by green and blue light, whereas carotenogenesis is only induced by blue light. The blue regulation of both responses suggests the existence of blue-light photoreceptors in M. circinelloides. Three white collar-1 genes (mcwc-1a, mcwc-1b and mcwc-1c) coding for proteins showing similarity with the WC-1 photoreceptor of Neurospora crassa have been identified. All three contain a LOV (light, oxygen or voltage) domain, similar to that present in fungal and plant blue-light receptors. When knockout mutants for each mcwc-1 gene were generated to characterize gene functions, only mcwc-1c mutants were defective in light induction of carotene biosynthesis, indicating that mcwc-1c is involved in the light transduction pathway that control carotenogenesis. We have also shown that positive phototropism is controlled by the mcwc-1a gene. It seems therefore that mcwc-1a and mcwc-1c genes control different light transduction pathways, although cross-talk between both pathways probably exists because mcwc-1a is involved in the light regulation of mcwc-1c expression.
authors.affiliation: Departamento de Genética y Microbiología, Facultad de Biología, Universidad de Murcia, 30071 Murcia, Spain.
authors.forename: Fátima
authors.initials: F
authors.lastname: Silva
authors.forename: Santiago
authors.initials: S
authors.lastname: Torres-Martínez
authors.forename: Victoriano
authors.initials: V
authors.lastname: Garre
mesh_terms: D000595:Amino Acid Sequence; D002338:Carotenoids / Q000235:genetics; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics* / Q000502:physiology*; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics* / Q000502:physiology*; D017353:Gene Deletion; D015966:Gene Expression Regulation, Fungal; D008969:Molecular Sequence Data; D009089:Mucor / Q000235:genetics* / Q000502:physiology*; D009154:Mutation; D010641:Phenotype; D018524:Phototropism; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D015398:Signal Transduction; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics* / Q000502:physiology*
chemical_list: D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D014157:Transcription Factors; C105589:wc-1 protein, Neurospora crassa; D002338:Carotenoids