RESUMEN
The 63F early puff in the larval salivary gland polytene chromosomes contains the divergently transcribed E63-1 and E63-2 ecdysone-inducible genes. E63-1 encodes a member of the EF-hand family of Ca(2+)-binding proteins, while E63-2 has no apparent open reading frame. To understand the functions of the E63 genes, we have determined the temporal and spatial patterns of E63-1 protein expression, as well as undertaken a genetic analysis of the 63F puff. We show that E63-1 is expressed in many embryonic and larval tissues, but the third-instar larval salivary gland is the only tissue where increases in protein levels correlate with increases in ecdysone titer. Furthermore, the subcellular distribution of E63-1 protein changes dynamically in the salivary glands at the onset of metamorphosis. E63-1 and E63-2 null mutations, however, have no effect on development or fertility. We have characterized 40 kb of the 63F region, defined as the interval between Ubi-p and E63-2, and have identified three lethal complementation groups that correspond to the dSc-2, ida, and mge genes. We show that mge mutations lead to first-instar larval lethality and that Mge protein is similar to the Tom22 mitochondrial import proteins of fungi, suggesting that it has a role in mitochondrial function.
Asunto(s)
Proteínas de Drosophila , Drosophila/genética , Genes de Insecto , Proteínas de Transporte de Membrana , Mutación , Receptores de Superficie Celular , Secuencia de Aminoácidos , Animales , Secuencia de Bases , Proteínas de Unión al Calcio/genética , Proteínas de Unión al Calcio/metabolismo , Deleción Cromosómica , Mapeo Cromosómico , Cromosomas/genética , ADN Complementario/genética , Drosophila/crecimiento & desarrollo , Drosophila/metabolismo , Femenino , Regulación del Desarrollo de la Expresión Génica , Prueba de Complementación Genética , Hibridación in Situ , Proteínas de Insectos/genética , Proteínas de Insectos/metabolismo , Larva/crecimiento & desarrollo , Masculino , Proteínas de la Membrana/genética , Proteínas de la Membrana/metabolismo , Mitocondrias/metabolismo , Datos de Secuencia Molecular , Homología de Secuencia de AminoácidoRESUMEN
Early metamorphic development in Drosophila melanogaster is initiated by pulses of the steroid hormone ecdysone, which are transduced into tissue-specific transcriptional cascades. This process begins with the hormone-dependent activation of a set of transcription factors (early genes) that, in turn, activate set of tissue-specific effector genes (late genes). The 71E cytogenetic region of the salivary gland polytene genome contains several ecdysone-regulated transcription units. Molecular techniques were used to analyze these genes, their transcriptional program and their evolutionary relatedness. We find that this region contains a cluster of ten coordinately regulated late genes (L71 genes) that are organized as five divergently transcribed gene pairs. Maximum parsimony analysis suggests that an ancestral L71 gene duplicated to form the first gene pair which was, in turn, duplicated to form the set of gene pairs. The L71 gene products form a family of small, chemically basic proteins with a conserved backbone of cysteine residues. In addition, the 71E region contains another gene (I71-1) with the regulatory and biochemical characteristics of the salivary gland intermolt glue proteins.