The Gene Expression Program for the Formation of Wing Cuticle in Drosophila.

Lukasz F Sobala,Paul N Adler,Gregory P Copenhaver

doi:10.1371/journal.pgen.1006100

Abstract

The cuticular exoskeleton of insects and other arthropods is a remarkably versatile material with a complex multilayer structure. We made use of the ability to isolate cuticle synthesizing cells in relatively pure form by dissecting pupal wings and we used RNAseq to identify genes expressed during the formation of the adult wing cuticle. We observed dramatic changes in gene expression during cuticle deposition, and combined with transmission electron microscopy, we were able to identify candidate genes for the deposition of the different cuticular layers. Among genes of interest that dramatically change their expression during the cuticle deposition program are ones that encode cuticle proteins, ZP domain proteins, cuticle modifying proteins and transcription factors, as well as genes of unknown function. A striking finding is that mutations in a number of genes that are expressed almost exclusively during the deposition of the envelope (the thin outermost layer that is deposited first) result in gross defects in the procuticle (the thick chitinous layer that is deposited last). An attractive hypothesis to explain this is that the deposition of the different cuticle layers is not independent with the envelope instructing the formation of later layers. Alternatively, some of the genes expressed during the deposition of the envelope could form a platform that is essential for the deposition of all cuticle layers.

Highlights

The cuticular exoskeleton of insects provides multiple functions for the animal
We have characterized the gene expression pattern of wing epithelial cells over the period of cuticle formation and carried out transmission electron microscopy, which allows us to identify genes that likely play a role in the formation of different cuticle layers
We examined pupal wings by transmission electron microscopy (TEM) over the period covered by the RNAseq experiments allowing us to correlate the dramatic changes in gene expression with the morphological process of cuticle deposition

Summary

Introduction

The cuticular exoskeleton of insects provides multiple functions for the animal. It provides shape, protects the animal from the environment, limits water loss and provides the skeletal elements needed for locomotion. In different tissues of an individual animal the cuticle will have very different physical properties. The structure of the cuticle is as varied as its function and physical properties and is composed of multiple layers [1,2,3]. The number of layers and their thickness varies from one cuticle to another and insect cuticle has served as inspiration for a variety of human engineered material [4,5,6]

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Discussion

Conclusion