RESUMEN
Visual pigments (rhodopsins) are composed of a chromophore (vitamin A derivative) bound to a protein moiety embedded in the retinal membranes. Animals cannot synthesize the visual chromophore de novo but rely on the uptake of carotenoids, from which vitamin A is formed enzymatically by oxidative cleavage. Despite its importance, the enzyme catalyzing the key step in vitamin A formation resisted molecular analyses until recently, when the successful cloning of a cDNA encoding an enzyme with beta,beta-carotene-15,15'-dioxygenase activity from Drosophila was reported. To prove its identity with the key enzyme for vitamin A formation in vivo, we analyzed the blind Drosophila mutant ninaB. In two independent ninaB alleles, we found mutations in the gene encoding the beta,beta-carotene-15,15'-dioxygenase. These mutations lead to a defect in vitamin A formation and are responsible for blindness of these flies.
Asunto(s)
Ceguera/genética , Drosophila melanogaster/genética , Mutación , Oxigenasas/genética , Secuencia de Aminoácidos , Sustitución de Aminoácidos , Animales , Secuencia de Bases , Pollos , Clonación Molecular , Cruzamientos Genéticos , Proteínas de Drosophila , Drosophila melanogaster/enzimología , Femenino , Heterocigoto , Humanos , Masculino , Datos de Secuencia Molecular , Mutagénesis Sitio-Dirigida , Oxigenasas/química , Oxigenasas/metabolismo , Mutación Puntual , ARN Mensajero/genética , Proteínas Recombinantes/química , Proteínas Recombinantes/metabolismo , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Rodopsina/metabolismo , Alineación de Secuencia , Homología de Secuencia de Aminoácido , Vitamina A/biosíntesis , Deficiencia de Vitamina A , beta-Caroteno 15,15'-MonooxigenasaRESUMEN
The Drosophila ommatidia contain two classes of photoreceptor cells (PR's), the outer and the inner PR's. We performed an enhancer trap screen in order to target genes specifically expressed in PR's. Using the UAS/GAL4 method with enhanced green fluorescent protein (eGFP) as a vital marker, we screened 180000 flies. Out of 2730 lines exhibiting new eGFP patterns, we focused on 16 lines expressing eGFP in particular subsets of PR's. In particular, we describe three lines inserted near the spalt major, m-spondin and furrowed genes, whose respective expression patterns resemble those genes. These genes had not been reported to be expressed in the adult eye. These examples clearly show the ability of our screen to target genes expressed in the adult Drosophila eye.