Development and characterization of Act88F-GAL4 line that expresses GAL4 in Drosophila indirect flight muscles. H. Aonuma , H. Tsujimura. Developmental Biology, Tokyo Univ. Agri. Tech., Fuchu-shi, Tokyo, Japan.

   Previous reports suggest a signal from motor nerves to developing muscles to control their development. This is the case in Drosophila indirect flight muscles which develop during metamorphosis. If motor nerves that should innervate the muscles in the adult were cut in the larva, the muscles would not develop properly in the adult. In order to define the mechanism of this signaling in the indirect flight muscles, we developed a new GAL4 line that expressed GAL4 in these muscles, and characterized it in this study. We had expected the fly to be alive even with any mutation caused by ectopic gene expression. Regulatory region of Actin88F, which encodes a specific actin for indirect flight muscles, was used to control the GAL4 expression in this study. The region had been defined in a previous study (Hiromi and Hotta, 1985). The fly (Act88F-GAL4) we made had well developed indirect flight muscles with normal structure in gross anatomy and by microsections. Analysis using GFP as a reporter showed GAL4 expression began at APF24h in both DLMs and DVMs and continued to 7 days after eclosion, showing that this line expressed GAL4 properly in indirect flight muscles as we had expected. However, the fly showed some defect in the behavior and posture. They could not fly at all and some of them held the wings in abnormal position when walking. The GAL4 expression in indirect flight muscles started fading at 7 days after eclosion and entirely disappeared by 13 days after eclosion.We also observed GAL4 expression in some other muscles. Jump muscles began the expression at 7 days after eclosion, when the expression in direct flight muscles started fading. Leg muscles began at APF72h. And some small muscles in thoraces started the expression at 0 days and it continued to 13 days after eclosion.We are now examining the intracellular structure of the muscles.