Genetic variation for the positioning of wing veins in Drosophila melanogaster

To define the components of variation for wing shape in Drosophila in relat ion to what is known about the developmental control of wing patterning, we have characterized shape variation in the wings of 12 randomly chosen high ly inbred lines. Despite large differences in wing size between males and f emales, and between flies reared at 18 degrees C or 25 degrees C, wing shap e is remarkably unaffected by these variables and is highly line specific. The shape of each intervein region of the wing appears to be independently regulated at the genetic level, consistent with the role of secreted growth factors in establishing the locations of wing veins. Sex and temperature w ere found to have different effects on cell number in two intervein regions , with the result that wing shape is to a large extent independent of cell density. Dietary cholesterol was also shown to affect the breadth of the ce ntral intervein region, consistent with an effect on the strength of Hedgeh og signaling during wing development. We conclude that wing shape is under tighter genetic control than wing size, and hypothesize that this control i s achieved in large part by gene activity at the level of wing vein determi nation and differentiation.