How does membrane turnover relate with the turnover of the membrane's major constituents, the phospholipids? I pursued this question in investigations undertaken in collaboration with Prof. G. Y. Sun, Department of Biochemistry, University of Missouri. This is especially relevant since it also relates to visual transduction mechanisms. In Drosophila vision, one of the oldest and best studied mutants, norpA (no receptor potential), has a transduction defect involving phospholipase C (PLC). Because of this, the phospholipid and fatty acid composition of Drosophila heads was of interest. Major phospholipids were quantified in various mutants and were shown to turn over rapidly by labeling with radioactive phosphate, separation using thin layer chromatography (TLC), and quantification. Fatty acids of selected phospholipids were analyzed by gas chromatography (GC). Perhaps our most interesting finding was that there are no fatty acids longer than 18 carbons in fly heads. Although docosahexaenoic acid (22:6) is high in vertebrate photoreceptors, Drosophila heads had none. Neither is there arachidonic acid (20:4), a precursor of signaling molecules. Using several different media which differed in fatty acid composition, we showed that the fatty acid composition of the heads could be readily manipulated.

Papers on phospholipids and fatty acids:

Stark, W. S., Lin, T.-N., Brackhahn, D., Christianson, J. S., Sun, G. Y. Phospholipids in Drosophila heads: Effects of visual mutants and phototransduction manipulations . Lipids, 1993A, 28, 23-28. PubMed

Stark, W. S., Lin, T.-N., Brackhahn, D., Christianson, J. S., Sun, G. Y. Fatty acids in the lipids of Drosophila heads: Effects of visual mutants, carotenoid deprivation and dietary fatty acids. Lipids 1993B, 28,345-350. PubMed

We used eyes absent (eya), shown in this SEM, to selectively eliminate compound eyes in these studies. Eya lacks compound eyes but not simple eyes (ocelli)

A gas chromatogram showing thefatty acids (especially the lack of long chain fatty acids) in the Drosophilahead (from Stark et al., 1993B).

A thin layer chromatogram showingthe labeling pattern of lipids in the Drosophila head (from Starket al., 1993A).

This page was last updated on June, 22, 2005

return to Stark home page