PHENOTYPIC AND MOLECULAR CHARACTERIZATION OF CROAKER, A NEW MATING-BEHAVIOR MUTANT OF DROSOPHILA-MELANOGASTER

Mating of Drosophila melanogaster is a stereotypically patterned behav ior consisting of a fixed sequence of actions that is primarily under genetic control. Although courtship can be easily monitored and quanti fied, little is known about its neural basis. To obtain a better under standing of cellular and molecular mechanisms underlying courtship, we have isolated mutants that disrupt specific aspects of mating behavio r. The croaker mutant was isolated from approximately 1,000 lines harb oring single P-element insertions by screening for aberrant courtship song: croaker males often generate polycyclic pulse song while most of the song pulses are monocyclic in the wild-type. The mutant is also d efective in flight. Intracellular recordings of excitatory junction po tentials from larval body wall muscles and Ca++ action potentials from adult indirect flight muscles demonstrated that neuromuscular transmi ssion and Ca++ electrogenesis in the muscle fibers are not impaired by the croaker mutation. To define the croaker gene molecularly, genomic DNA surrounding the P-element insertion site was cloned by plasmid re scue and subsequent screening of a cosmid library. Northern blotting w ith the genomic DNA probes detected three transcripts in the wild-type , which were not expressed in the croaker mutant.