RESUMO
At the onset of Drosophila metamorphosis, the steroid hormone 20-OH ecdysone directly induces a small number of early puffs in the polytene chromosomes of the larval salivary gland. Proteins encoded by the early genes corresponding to these transcriptional puffs then regulate the activity of both the early puffs themselves and a much larger set of late puffs. Three of these early genes encode transcription factors that play critical regulatory roles during metamorphosis. Here we report the cloning, DNA sequence, genomic structure, ecdysone inducibility, and temporal expression of an early gene residing in the 23E early puff and denoted E23 (Early gene at 23). In contrast to other early genes, E23 encodes a protein with similarity to ATP-binding cassette transporters. Using heat shock-inducible transgenes, we found that E23 overexpression not only produces phenotypic abnormalities and lethality, but also interferes with ecdysone-mediated gene activation, demonstrating that E23 is capable of modulating the ecdysone response. Our results suggest the existence of a previously unrecognized regulatory mechanism for modulating steroid hormone signaling in Drosophila.
Assuntos
Transportadores de Cassetes de Ligação de ATP/metabolismo , Proteínas de Drosophila , Drosophila melanogaster/genética , Ecdisona/antagonistas & inibidores , Genes de Insetos/genética , Proteínas de Insetos/metabolismo , Metamorfose Biológica/genética , Ativação Transcricional , Transportadores de Cassetes de Ligação de ATP/química , Transportadores de Cassetes de Ligação de ATP/genética , Sequência de Aminoácidos , Animais , Clonagem Molecular , Drosophila melanogaster/efeitos dos fármacos , Drosophila melanogaster/crescimento & desenvolvimento , Drosophila melanogaster/metabolismo , Ecdisona/farmacologia , Perfilação da Expressão Gênica , Genes Letais/genética , Proteínas de Insetos/química , Proteínas de Insetos/genética , Larva/efeitos dos fármacos , Larva/genética , Metamorfose Biológica/efeitos dos fármacos , Dados de Sequência Molecular , Família Multigênica/genética , Fenótipo , Pupa/efeitos dos fármacos , Pupa/genética , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Alinhamento de Sequência , Transcrição Gênica/efeitos dos fármacos , Transcrição Gênica/genética , Ativação Transcricional/efeitos dos fármacosRESUMO
Evaluations of sires for milk yield by contemporary comparison were used to determine factors associated with changes of evaluation over time. Changes in paired evaluations for 160 Holstein sires were final evaluations (Repeatability exceeding 90%) minus initial evaluations (Repeatability less than 70%). Multiple regression procedures were used to relate characteristics of initial sampling programs to changes in evaluations. Characteristics of initial evaluations associated with more stable evaluations included greater Repeatability for sires evaluated and for sires of contemporaries, higher producing, smaller sized herds with lower genetic merit of contemporaries, and less variation across herd-year-seasons in number of contemporary sires and producing ability of mates. Initial evaluations tending to increase over time were those from large herds of below average genetic merit (for contemporary sires) with greater than average variation in Repeatability of contemporary sires and less than average variance in number of contemporary sires and producing abilities of mates. Results suggested that most changes in evaluations of sires are from Mendelian sampling but that modest increases in stability of evaluations may be achieved through altered design of initial progeny testing programs.
