RESUMO
Many developmental processes of multicellular organisms involve the patterning and growth of two-dimensional tissues, so called epithelia. We have quantified the growth of the wing imaginal disk, which is the precursor of the adult wing, of the fruit fly Drosophila melanogaster. We find that growth follows a simple rule with exponentially decreasing area growth rate. Anisotropies of growth can be precisely determined by comparing experimental results to a continuum theory. Growth anisotropies are to good approximation constant in space and time. They are weak in wild-type wing disks but threefold increased in GFP-Dpp disks in which the morphogen Dpp is overexpressed. Our findings indicate that morphogens such as Dpp control tissue shape via oriented cell divisions that generate anisotropic growth.
Assuntos
Drosophila/crescimento & desenvolvimento , Epitélio/crescimento & desenvolvimento , Morfogênese/fisiologia , Asas de Animais/crescimento & desenvolvimento , Animais , Divisão Celular , Drosophila/anatomia & histologia , Drosophila/citologia , Drosophila/metabolismo , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Epitélio/anatomia & histologia , Epitélio/metabolismo , Regulação da Expressão Gênica no Desenvolvimento/genética , Regulação da Expressão Gênica no Desenvolvimento/fisiologia , Proteínas de Fluorescência Verde/química , Proteínas de Fluorescência Verde/metabolismo , Morfogênese/genética , Fatores de Tempo , Asas de Animais/anatomia & histologia , Asas de Animais/citologia , Asas de Animais/metabolismoRESUMO
In the wing imaginal disc of Drosophila melanogaster, the morphogen Dpp controls growth, probably in an instructive manner. Many models for growth control by Dpp have been proposed and have been extensively discussed elsewhere. In this review, we speculate on how instructive growth control could provide a link between Dpp signaling and cell growth and/or cell cycle progression and so implement morphogenetic growth control on the cellular and molecular levels.
Assuntos
Proteínas de Drosophila/metabolismo , Drosophila melanogaster/embriologia , Discos Imaginais/crescimento & desenvolvimento , Morfogênese/genética , Asas de Animais/crescimento & desenvolvimento , Animais , Ciclo Celular , Divisão Celular , Proliferação de Células , Proteínas de Drosophila/genética , Drosophila melanogaster/citologia , Drosophila melanogaster/genética , Regulação da Expressão Gênica no Desenvolvimento , Discos Imaginais/citologia , Transdução de Sinais , Asas de Animais/citologiaRESUMO
Morphogens, such as Decapentaplegic (Dpp) in the fly imaginal discs, form graded concentration profiles that control patterning and growth of developing organs. In the imaginal discs, proliferative growth is homogeneous in space, posing the conundrum of how morphogen concentration gradients could control position-independent growth. To understand the mechanism of proliferation control by the Dpp gradient, we quantified Dpp concentration and signaling levels during wing disc growth. Both Dpp concentration and signaling gradients scale with tissue size during development. On average, cells divide when Dpp signaling levels have increased by 50%. Our observations are consistent with a growth control mechanism based on temporal changes of cellular morphogen signaling levels. For a scaling gradient, this mechanism generates position-independent growth rates.