ASGSB 1998 Annual Meeting Abstracts

[77]
GENETIC CONTROL OF OSMOREGULATION IN DROSOPHILA.   X. Huang, L. Huff, Q. Huang and M. Stern, Dept. of Biochemistry, Rice University, Houston TX 77251

One mechanical stress that can be sensed by all cells is osmotic stress, which is applied when a cell is exposed to a non-isotonic extracellular environment. Exposure to such an environment causes major water and ion fluxes across the cell membrane, changes in cell volume, and thus causes forces to be applied to the cell membrane.

Knowledge of the molecular mechanisms by which cells respond to changes in osmolarity would not only be useful in understanding osmotic stress response, but also cellular responses to other mechanical forces on the cell. We are currently studying the molecular mechanisms underlying osmotic stress response in Drosophila. Our starting point for these studies is the inebriated (ine) gene, which encodes a member of the Na⁺/Cl- dependent family of neurotransmitter/osmolyte transporters. Among other functions, members of this family transport osmolytes such as betaine across cell membranes; this osmolyte accumulation enables cells to withstand a hypertonic environment. By in situ hybridization to developing Drosophila embryos, we found that this transporter is transcribed in two cell types that perform fluid reabsorption in insects: the Malpighian tubule and the hindgut. These tissues together comprise the invertebrate analogue of the mammalian kidney. This observation raises the possibility that the ine-encoded transporter might perform osmolyte transport and enable the fly to survive a hypertonic environment. This possibility is supported by our observation that ineбmutants are much less viable than wildtype when grown on high [NaCl] or [sorbitol]. We are currently using the lethality of ineбmutants on salt to isolate mutations that suppress this phenotype. The genes identified by such suppressors might encode additional molecules controlling the osmotic stress response in Drosophila.

(Supported by NASA grant NAGW-5007)

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