Date of Award:
5-1-1969
Document Type:
Dissertation
Degree Name:
Doctor of Philosophy (PhD)
Department:
Biology
Department name when degree awarded
Zoology
Committee Chair(s)
J. R. Simmons
Committee
J. R. Simmons
Committee
James T. Bowman
Committee
E. J. Gardner
Committee
R. T. Sanders
Committee
R. S. Spendlove
Abstract
A model for the synthesis of the brown insect pigment, xanthommatin, has been proposed by Butenandt, Biekert, and Linzen (1956). This model states that two molecules of 3-hydroxykynurenine condense in the presence of a phenol oxidase catalyzed dopa-dopaquinone redox system to form one molecule of xanthommatin. Two criteria have been used in this investigation to determine the validity of the model as applied to xanthommatin synthesis in Drosophila melanogaster. (1) Does the model provide a basis for the action of mutants, such as scarlet (st), cardinal (cd), and lightoid (ltd), which block the conversion of 3-hydroxykynurenine to xanthommatin? (2) Does the model provide a mechanism for the developmental regulation of xanthommatin synthesis? Neither st nor ltd produce detectable amounts of 3-hydroxykynurenine or xanthurenic acid at any point during development. Cardinal accumulates 3-hydroxykynurenine from pupal into adult life. None of these mutants can convert injected 3-hydroxykynurenine to xanthommatin. The failure of these mutants to convert 3-hydroxykynurenine to xanthommatin is not due to alterations of the dopa-dopaquinone redox system. Developmental profiles of phenol oxidase activity of the mutants are not significantly different from wild type and there is no indication of lack of dopa in the mutants. Thus, the criterion that the model must provide a basis for the action of mutants unable to convert 3-hydroxykynurenine to xanthommatin is not satisfied. Likewise, the model does not provide a mechanism for the developmental regulation of xanthommatin synthesis. All of the components of the model system necessary for xanthommatin synthesis are present in larvae and early pupae prior to normal synthesis. Thus, the criterion that the model must provide a mechanism for the regulation of xanthommatin synthesis is not satisfied. Although these data do not demonstrate that the proposed mechanism for xanthommatin synthesis is invalid, they do show that synthesis of xanthommatin in vivo requires more than the presence of 3-hydroxykynurenine and a phenol oxidase catalyzed dopa-dopaquinone redox system.
Recommended Citation
Phillips, John P., "The Problem of Terminal Xanthommatin Synthesis in Drosophila" (1969). Biology. 363.
https://digitalcommons.usu.edu/etd_biology/363
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