Eye color brown at eclosion, darkening to sepia, and
becoming black with age. Thought to be the structural gene
for the enzyme PDA synthetase which catalyzes the conversion
of 6-pyruvoyltetrahydropterin to 2-amino-4-oxo-6-acetyl-7,8-dihydro-3H,9H-pyrimido [4, 5, 6]-[1, 4] diazepine (=PDA),
which is a precursor of the red drosopterin pigments. The
enzyme has been partially purified and has a molecular weight
of 48,000 daltons (Wiederrecht and Brown, 1984, J. Biol. Chem.
259: 14121-27). Pigment of ocelli normal. Chromatographically, se eyes characterized by having no red pigment [e.g.
drosopterin and isodrosopterin (McKay, 1972, DIS 48: 62)] and
an accumulation of yellow pigment (Hadorn and Mitchell, 1951,
Proc. Nat. Acad. Sci. USA 37: 650-65; Ziegler-Gunder and
Hadorn, 1958, Z. Vererbungsl. 89: 235-45). Three yellow pigments identified are 6- derivatives of 2-amino-4-hydroxy-7,8-dihydropteridine; the most abundant is sepiapterin, the 6-lactyl derivative; minor species are isosepiapterin (Viscontini and Mohlmann, 1959, Helv. Chim. Acta 42: 836-41;
Forrest, VanBaalen, and Myers, 1959, Arch. Biochem. Biophys.
83: 508-20) and neosepiapterin (Takikawa, 1973, DIS 50: 158;
Sugiura, Takikawa, Tsusue, and Goto, 1973, Bull. Chem. Soc.
Jpn. 46: 3312-13), which are the 6-proprionyl and 6-acetyl
derivatives respectively; the latter compound shown to be D-erythro-neopterin by Katoh and Arai (1974, DIS 51: 70).
Other pteridines present in greater-than-normal amounts [e.g.
isoxanthopterin II, xanthopterin I, and biopterin (McKay)].
Eye color autonomous in se eye disks transplanted into wildtype hosts (Beadle and Ephrussi, 1936, Genetics 21: 230). pn
se flies have 10% amount of sepiapterin of se alone (Lifschytz
and Falk, 1969, Genet. Res. 14: 53-61); dor se displays
reduced viability (Lucchesi, 1968, Genetics 59: 37-44). RK1.