Genetic Control of Tissue Specific Growth in the Drosophila Trachea

Abstract

In most organisms, different tissues and organs grow at different rates relative to each other, suggesting underlying growth mechanisms that act tissue specifically. The mechanisms of tissue specific growth are less well understood than those governing the growth of an entire organism. To gain a better understanding of these tissue specific growth mechanisms, our lab has characterized mutations that specifically alter the growth of the larval trachea in Drosophila melanogaster. Larval trachea growth is well suited for these studies since the trachea shows allometric growth during the larval stages, can be imaged and measured in living animals and gene expression can be specifically altered in the trachea using breathless-GAL4. Importantly, we and others have identified mutations in genes whose mutant phenotypes suggest that they normally regulate tissue-specific growth in the larval trachea. For example, animals with mutations in uninflatable (uif) and Matrix metalloproteinase 1 (Mmp1) have larval tracheae that are roughly half the relative size of those in wild type animals. Here we report the results of a screen of EMS-induced larval lethal mutations that recovered seven different alleles that cause either overgrowth or undergrowth of the larval trachea. Three of these mutations form one complementation group, and we have used complementation mapping and RNA interference to show that the affected gene is CG11340. This gene encodes a glycine gated chloride channel previously thought to function only in neurotransmitters. We have named this gene rio based upon its long and convoluted tracheal phenotype. Here we show its function as a negative growth regulator in the trachea and demonstrate its interaction with the previously characterized positive growth regulators in tracheal specific growth.