Temporal Control of Puffing Activity in Polytene Chromosomes

Discrete pulses of molting hormone, 20‐hydroxyecdysone, during late larval development of Drosophila melanogaster: Correlations with changes in gene activity

“…This has been especially true for the critical third (final) larval instar when the insect must be reprogrammed so that it can undergo metamorphosis to the pupa and then the adult in response to a large surge in 20E, a phenomenon studied mainly in the Lepidoptera (Bollenbacher et al, 1975;Riddiford, 1976Riddiford, , 1995. The requisite involvement of ecdysteroid signaling in these complex processes is central to present theories of arthropod development (Ashburner et al, 1974;Yao et al, 1993;Buszczak and Segraves, 1998;Bialeccki et al, 2002;Lafont et al, 2005;Henrich, 2005). However, the RIA, particularly when applied directly to whole body extracts, yields only a rough estimate of the molting hormone titer, as each ecdysteroid component present gives a variable response (cross-reactivity) in the assay depending on affinity characteristics of the antibody used.…”

Sequence and functional properties of Ets genes in the model organism Drosophila

“…Likewise, early and late pu s are also observed around the time of the prepupa to pupa transition in response to a later rise in ecdysone titer. Ashburner et al (1974) proposed a model wherein the ecdysone-receptor complex induces genes within the early pu s and the products of these primary activated genes subsequently activate the late genes while repressing their own activity. Detailed molecular and genetic analyses have validated this model, not only for the ecdysone regulated changes in gene expression in salivary glands, but also for other larval tissues that must be eliminated during the process of metamorphosis Fletcher et al, 1995).…”

The timing of Drosophila salivary gland apoptosis displays an l(2)gl-dose response

“…11,12 Based on the sequence of polytene chromosome puffings occurring during late larval and prepupal development, 13,14 a two-step regulatory hierarchy of early and late gene expression was proposed to account for the events that precede metamorphosis and the death of the salivary glands. 15,15 The expression of early genes, which is directly induced by the ecdysone-receptor complex, gives rise to the synthesis of a variety of proteins, including transcription factors, which trigger late gene expression. In turn the products of these genes are thought to induce expression of death genes, such as reaper (rpr), head involution defective (hid), and grim, which act as mediators between different signalling pathways and apoptosis implemented by caspases.…”