RESUMEN
The evolutionary differences in sensory bristle patterns on the thorax of dipterans are an excellent model for studying the patterns of evolutionary development. We observed that Drosophila melanogaster has two pairs of the large bristles, called macrochaetes, in the dorsocentral (DC) region of the notum, while Musca domestica retains six DC macrochaetes. To explore possible mechanism by which these two dipteran species have different numbers of DC bristles, we compared the corresponding protein sequences, the gene expression levels and the spatial expression patterns of five genes (scute, pnr, ush, hairy, and emc) for bristle development between two species. We also checked the overexpression of scute and emc in transgenic flies. The results demonstrated a strong conservation of five protein sequences between these two species. The mRNA expression of the five genes differed significantly between D. melanogaster and M. domestica. The gene expression patterns exhibited a species-specific pattern during the larval development stage. It suggests that the function of these genes has been conserved in regulating the development of macrocheates between housefly and fruit fly, whereas the gene expression levels, especially spatial expression patterns lead to species-specificity in DC bristles.
Asunto(s)
Tipificación del Cuerpo/genética , Evolución Molecular , Regulación del Desarrollo de la Expresión Génica , Tórax/embriología , Animales , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/química , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/genética , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/metabolismo , Secuencia Conservada , Proteínas de Unión al ADN/química , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/metabolismo , Proteínas de Drosophila/química , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/embriología , Drosophila melanogaster/genética , Ratones , Proteínas Represoras/química , Proteínas Represoras/genética , Proteínas Represoras/metabolismo , Células Receptoras Sensoriales/citología , Células Receptoras Sensoriales/metabolismo , Tórax/metabolismo , Factores de Transcripción/química , Factores de Transcripción/genética , Factores de Transcripción/metabolismoRESUMEN
The wings of butterflies and moths consist of dorsal and ventral epidermal surfaces that give rise to overlapping layers of scales and hairs (Lepidoptera, "scale wing"). Wing scales (average length ~200 µm) are homologous to insect bristles (macrochaetes), and their colors create the patterns that characterize lepidopteran wings. The topology and surface sculpture of wing scales vary widely, and this architectural complexity arises from variations in the developmental program of the individual scale cells of the wing epithelium. One of the more striking features of lepidopteran wing scales are the longitudinal ridges that run the length of the mature (dead) cell, gathering the cuticularized scale cell surface into pleats on the sides of each scale. While also present around the periphery of other insect bristles and hairs, longitudinal ridges in lepidopteran wing scales gain new significance for their creation of iridescent color through microribs and lamellae. Here we show the dynamics of the highly organized F-actin filaments during scale cell development, and present experimental manipulations of actin polymerization that reveal the essential role of this cytoskeletal component in wing scale elongation and the positioning of longitudinal ribs.
Asunto(s)
Actinas/metabolismo , Mariposas Diurnas/crecimiento & desarrollo , Aumento de la Célula , Morfogénesis/fisiología , Alas de Animales/crecimiento & desarrollo , Animales , Mariposas Diurnas/metabolismo , Quitina/metabolismo , Microscopía Confocal , Microscopía Electrónica de Rastreo , Faloidina , Factores de Tiempo , Aglutininas del Germen de Trigo , Alas de Animales/metabolismo , Alas de Animales/ultraestructuraRESUMEN
A strictly determined number of external sensory organs, macrochaetes, acting as mechanoreceptors, are orderly located on drosophila head and body. Totally, they form the bristle pattern, which is a species-specific characteristic of drosophila.Each mechanoreceptor comprises four specialized cells derived from the single sensory organ precursor (SOP) cell. The conserved bristle pattern combined with a comparatively simple structure of each mechanosensory organ makes macrochaetes a convenient model for studying the formation spatial structures with a fixed number of elements at certain positions and the mechanism underlying cell differentiation.The macrochaete morphogenesis consists of three stages. At the first stage, the proneural clusters segregate from the massive of ectodermal cells of the wing imaginal disc. At the second stage, the SOP cell is determined and its position in the cluster is specified. At the third stage, the SOP cell undergoes two asymmetric divisions, and the daughter cells differentiate into the components of mechanoreceptor: shaft, socket, bipolar neuron, and sheath.The critical factor determining the neural pathway of cell development is the content of proneural proteins, products of the achaete-scute (AS-C) gene complex, reaching its maximum in the SOP cell.The experimental data on the main genes and their products involved in the control of bristle pattern formation are systematized. The roles of achaete-scute complex, EGFR and Notch signaling pathways, and selector genes in these processes are considered. An integral scheme describing the functioning of the system controlling macrochaete development in D. melanogaster is proposed based on analysis of literature data.