Studies on Learning and Cyclic AMP Phosphodiesterase of the Dunce Mutant of Drosophila melanogaster

Author: Byers, Andrew Duncan

Year: 1980

Degree: Dissertation (Ph.D.)

Advisor: Benzer, Seymour

Committee Members: Benzer, Seymour; Hudspeth, A. James; Konishi, Masakazu; Konopka, Ronald J.; Lewis, Edward B.; Olds, James

Option: Biology

DOI: 10.7907/k8cd-wk36

Abstract

Normal Drosophila learn to avoid an odorant associated with electric shock. This dissertation describes the isolation of two x-linked mutants that fail to display this learning, in spite of being able to sense the odorants and electric shock. The mutants are proved to be alleles of one gene, and are named dunce1 and dunce2. The finding that dunce2 females are sterile led to the discovery that the dunce gene was independently known in two other laboratories.

Kiger, Davis, and Golanty of the University of California at Davis find (one) that normal Drosophila have two forms (I and II) of soluble cyclic AMP phosphodiesterase, differing in molecular weight and other properties; (two) that a gene appearing to control form II is included within chromosomal bands 3D3 and 3D4; and (three) that females with homozygous deficiency of these two bands are sterile. Mohler of the University of Iowa isolated 225 x-linked female-sterile mutants. Among these Davis and Kiger found two that map within 3D3 and 3D4 and lack the form II of soluble cyclic AMP phosphodiesterase.

The two mutants of Mohler learn poorly. They do not complement dunce1 or dunce2 in learning nor dunce2 in fertility, and therefore are alleles of the dunce gene. Mapping of learning with genetic deficiencies and duplications places dunce1 and dunce2 within region 3D3 and 3D4. Females with homozygous deficiency of five adjacent bands, including these two, are viable and vigorous, but learn poorly and are sterile.

The soluble cyclic AMP phosphodiesterase II is inactive or absent in homogenates of dunce1 and dunce2 flies. In addition, cyclic AMP levels are elevated in the dunce mutants, as expected if cyclic AMP phosphodiesterase activity is deficient.

It is concluded that the dunce gene of normal Drosophila has functions in olfactory learning performance, reproduction, and cyclic AMP metabolism. Recent work with other organisms has suggested that cyclic AMP may be intimately involved in mechanisms of learning; the dunce mutant should prove helpful in testing this.

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