Host - transplant Interactions in Biosynthesis of Drosophila Pteridines

A SERIES of fluorescent pteridines may be revealed and separated by paper chromatography (Hadorn & Mitchell, 1951) from various organs of Drosophila in which they appear in high concentrations. Striking differences in the quantities and in the developmental patterns of these compounds are produced by a variety of gene mutations. While the chemical analysis of the fluorescent substances is rapidly progressing (cf. Forrest & Mitchell, 1955; Viscontini et al, 1955; Viscontini, 1958) the information on the mode and the sites of their biosynthesis is, as yet, extremely scanty. The only well-established reaction involving two of the more abundant pteridines is the enzymatic conversion of 2-amino-4-hydroxy-pteridine (HBi) to isoxanthopterin (IX) in the presence of the enzyme xanthine dehydrogenase (Forrest, Glassman, & Mitchell, 1956). The importance of this reaction in vivo could be demonstrated by experiments with the mutant rosy iry) which is devoid of the enzyme (Hadorn & Schwinck, 1956; Hadorn & Graf, 1958; Hadorn, Graf, & Ursprung, 1958). Normalization of IX content in rosy eye-disks or testes transplanted into the abdomen of a wild-type host was found to be correlated with a decrease in the concentration of the precursor substance HBi. Furthermore, injections of HBi into wild-type larvae leads to an increase in the IX content of the developing pupae (Graf, Hadorn, & Ursprung, 1959). The synthesis of the more complex red eye-pigments (drosopterines = DP; cf. Viscontini, Hadorn, & Karrer, 1957) might be assumed to be closely associated with that of IX, because defects and repairs in both fractions appear to be intimately coupled in the mutants rosy (Hadorn & Schwinck, 1956) and maroon-like (Glassman, Forrest, & Mitchell, 1957). In these genotypes the absence of IX is accompanied by a severe reduction in red pigments, while experimental transfer of eye-tissue to a wild-type host results in concurrent normalization of both deficiencies. It should be noted, however, that other eyecolour mutants like se (Hadorn & Ziegler-Giinder, 1958) and Pm (Ronen, 1957)