RESUMO
Prior to completion, apoptosis causes the secretion of different signals, including proliferative signals. Signaling associated with death was discovered in Drosophila and mostly characterized by the induction of experimental death. Thus, less is known about physiological death. Here, we analyzed physiological death in the genital disc, a structure with bilateral symmetry, in different growth scenarios. To this end, we prevented or promoted death in regions or in genetic mosaics. We observed that physiological death in the genital disc was associated with proliferative signals and that both processes were JNK-dependent. The proliferative signals promoted growth in the genitalia primordia but not in the analia. Due to the proliferative signaling, the prevention of death that produced undead cells provoked asymmetric growth, high variability in proliferation, and size reduction. Death can occur in the absence of JNK but without signaling. JNK is fundamental for growth and death associated with signaling.
Assuntos
Apoptose , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/crescimento & desenvolvimento , Genitália Feminina/crescimento & desenvolvimento , Genitália Masculina/crescimento & desenvolvimento , Proteínas Quinases JNK Ativadas por Mitógeno/metabolismo , Animais , Proliferação de Células , Drosophila melanogaster/genética , Drosophila melanogaster/metabolismo , Feminino , Genitália Feminina/metabolismo , Genitália Feminina/patologia , Genitália Masculina/metabolismo , Genitália Masculina/patologia , Masculino , Diferenciação Sexual , Transdução de SinaisRESUMO
There are different models that explain growth during development. One model is based on insect and amphibian regeneration studies. This model proposes that growth is directed by pattern, and growth takes place by intercalation at a growth discontinuity; therefore, proliferation should surround the discontinuity. Currently, this model, apart from regenerative studies on mostly adult patterning, has not found supporting evidence in Drosophila that shows proliferation surrounding a discontinuity. Despite this lack of evidence, the importance of discontinuities has been shown in different experiments, even under wt conditions, more specifically in the formation of the leg joints because of the occurrence of cell death at their boundaries. Here, we show the existence of a sharp discontinuity in Decapentaplegic (Dpp) in the genital discs at the third larvae stage (L3), which determines the upregulation in the Jun-NH2-Terminal-Kinase (JNK) pathway, reaper (rpr), head involution defective (hid) and active caspases from its boundaries. The proliferation and cell death surrounding the discontinuity suggest that growth can proceed by intercalation and competitive death takes place in this area. Finally, we show that the Rpr, Grim and Hid (RGH) products are a few of the factors that define the growth discontinuity because they are negative regulators of growth, a new function that is unique from their known functions in apoptosis.