The induction of DNA puff BhC4-1 gene is a late response to the increase in 20-hydroxyecdysone titers in last instar dipteran larvae

Abstract

The characterization of DNA puff BhC4-1 expression was extended and its response to 20-hydroxyecdysone investigated in Bradysia hygida and in transgenic Drosophila carrying the BhC4-1 gene. In both organisms the activation of BhC4-1 in salivary glands occurs at the end of the larval stage coinciding with the peak in ecdysone titers which induces metamorphosis. Injections of 20-hydroxyecdysone into mid-fourth instar larvae of B. hygida show that the induction of BhC4-1 expression, as well as amplification and puff C4 expansion, are late events induced by the hormone. This late response of BhC4-1 expression was also observed in transgenic salivary glands cultivated in the presence of 20-hydroxyecdysone. In vitro studies using transgenic Drosophila indicate that both repressor and activator factors regulate the timing of BhC4-1 expression in salivary glands.

Functional and bioinformatics analyses reveal conservation of cis‐regulatory elements between sciaridae and drosophilidae

“…V INTRODUCTION DNA puffs are a feature of the Sciaridae family and are formed at discrete sites during the fourth larval instar in the salivary gland polytene chromosomes. These genomic regions constitute sites of developmentally regulated gene amplification and transcription (Basso et al, 2002;Foulk et al, 2006;Gerbi et al, 1993;Lara et al, 1991;Stocker et al, 1996). The formation of DNA puffs is induced by ecdysone and is concomitant with the transcription of the genes which present the highest levels of amplification within the amplicons (Fontes et al, 1992;Gerbi et al, 1993;Glover et al, 1982;Paçó-Larson et al, 1992;Penalva et al, 1997;Santelli et al, 1991Santelli et al, , 2004Wu et al, 1993;Yokosawa et al, 1999).…”

“…The BhC4-1 DNA puff gene of Bradysia hygida is amplified 21-fold and abundantly transcribed in the salivary gland when DNA puff C4 is formed at the end of the fourth larval instar (Basso et al, 2002;Paçó-Larson et al, 1992). DNA puff C4 formation and the amplification and expression of the BhC4-1 gene are all induced as a late response to the increase of ecdysone titers that triggers metamorphosis (Basso et al, 2002).…”

“…DNA puff C4 formation and the amplification and expression of the BhC4-1 gene are all induced as a late response to the increase of ecdysone titers that triggers metamorphosis (Basso et al, 2002). The availability of a transformation system and mutant collections, coupled to genomic information in the model system Drosophila melanogaster, prompted us to perform functional assays of DNA puff genes in a transgenic context.…”

“…The availability of a transformation system and mutant collections, coupled to genomic information in the model system Drosophila melanogaster, prompted us to perform functional assays of DNA puff genes in a transgenic context. In transgenesis, BhC4-1 expression in the salivary glands is a late response to the increase in ecdysone titers at the onset of metamorphosis (Basso et al, 2002;Monesi et al, 1998). Genetic interaction experiments have demonstrated that the products of the ecdysoneinduced early genes, BR-C, E74, and E75 participate to differing extents in the induction of BhC4-1-lacZ in the salivary gland (Basso et al, 2006).…”

Genome size of three Brazilian flies from the Sciaridae family

“…The invertebrates constitute the major form of multicellular life but the genome size of only about 1,300 invertebrate species is available in Gregory's Animal Genome Size Database (Gregory 2001). For Diptera, the genome size has been described for only 12 families, mainly Drosophilidae and Cullicidae, but no data is available for other dipteran families such as the Sciaridae although insects of this family have been widely used in molecular and cell biology research (Fiorini et al, 2001;Basso Jr. et al, 2002;Monesi et al, 2003;Soares et al, 2003) and the description of their genome size is not only important in these research areas but it could also help in the solution of evolutionary questions relating to the Diptera. The aim of the study presented in this paper was to contribute to the data on insect genome size by determining the DNA content and the genome size of the Brazilian sciarids Bradysia hygida, Rhynchosciara americana and Trichosia pubescens using absorbance measurements of Feulgen-stained neuroblast nuclei from larvae of these species.…”