A screen to identify genes involved in tissue specific growth of the larval trachea in Drosophila. Paulo Leal, Robert Ward. Dept Molecular Biosciences, University of Kansas, Lawrence, KS.

   During post-embryonic development in animals, different tissues and organs grow at different rates relative to each other, likely tied to the unique requirements of each organs function during development and homeostasis. Differential growth occurs in spite of the fact that overall growth is tied to nutrition, which is largely regulated through the insulin signaling pathway. This suggests that there must be tissue-specific mechanisms that function in concert with or in parallel to insulin signaling to control their post-embryonic growth, although we know very little about them. One way to understand these mechanisms is through the characterization of mutations that specifically alter growth in single organs or tissues in a genetically tractable model system. The larval trachea of Drosophila is well suited for this study as it is a well-studied branched tubular organ required for gas exchange that grows dramatically during larval development. Embryonic tracheal development is genetically controlled to yield tubes of appropriate caliber to support gas movement throughout the newly hatched larva. Upon hatching, however, the larva begins to feed and thus organ growth is tied to nutrition. Mutations in two genes, uninflatable (uif) and Matrix metalloproteinase 1 (Mmp1) have phenotypes that include tissue specific growth reductions within the larval trachea. To identify additional genes that regulate larval tracheal growth, we are screening two collections of late lethal mutations: 49 P-element induced late larval lethals obtained from the Bloomington stock center and 252 EMS induced larval/pupal lethals from the collection of 3rd chromosome late lethals generated by Dr. Bashirullah (University of Wisconsin). Preliminary screening identified 2 P-element and 4 EMS mutations that show specific larval tracheal defects, including both reduced and expanded relative tracheal sizes. We are mapping and conducting phenotypic analysis on the mutant larvae, and examining interactions between uif, Mmp1, and the isolated mutants.