You may have noticed that Drosophila melanogaster body color can come in a few different shades. The wild-type (normal) coloration that you’ll typically see is tan, as in the image below.
But there are several other body colors, namely a lighter yellow (due to mutation of the yellow gene) and darker ebony (due to mutation of the ebony gene), nicely illustrated in the image below. You’ll also notice that in yellow and ebony mutant flies, these changes in coloration extend to the wings as well.1
Biochemical pathway for Drosophila melanogaster body coloration
So how does this variety of body colors come about? The biochemical pathway underlying Drosophila melanogaster body coloration has been painstakingly dissected, and is regulated by several different genes. In D. melanogaster, body coloration is determined by four pigments: Two melanins (brown and dark black), and two scelarotins (tan-yellow and colorless). The correct balance of these four produces the wild-type fly’s body color.2
The process begins with the amino acid tyrosine, obtained from the fly’s diet. This is converted into DOPA (L-3,4-dihydroxyphenylalanine) by tyrosine hydroxylase (TH) protein. This DOPA is then further converted into dopamine through a reaction catalyzed by the dopa decarboxylase enzyme, encoded by the ddc gene.
As you can see in the schematic above, the Yellow protein (encoded by the yellow gene) regulates production of the Black pigment from DOPA, while the Ebony protein (encoded by the ebony gene) regulates the enzymatic pathway responsible for yellow pigment (NBAD scelarotin) production. This explains why mutation in yellow results in loss of Black pigment and therefore a lighter, yellow body color. (Read my previous post for a full overview of the philosophy behind Drosophila melanogaster gene naming).
These different strains of D. melanogaster have been studied for decades, their pigmentation patterns helping to reveal the details of these important biochemical pathways. Now you know the details of Drosophila melanogaster body color!
- Patricia J. Wittkopp, John R. True, Sean B. Carroll; Reciprocal functions of the Drosophila Yellow and Ebony proteins in the development and evolution of pigment patterns. Development 15 April 2002; 129 (8): 1849–1858. doi: https://doi.org/10.1242/dev.129.8.1849
- Massey J and Wittkopp PJ. The genetic basis of pigmentation differences within and between Drosophila species. Curr Top Dev Biol. 2016;119:27-61. doi:10.1016/bs.ctdb.2016.03.004