43rd ANNUAL DROSOPHILA RESEARCH CONFERENCE
April 10-14, 2002

PROGRAM AND ABSTRACT VOLUME
Workshop Abstract

10W
Host genetic effects on Wolbachia distribution and proliferation during spermatogenesis in Drosophila. M. Clark, T. Karr. Department of Organismal Biology & Anatomy, University of Chicago, IL.

Wolbachia, a cytoplasmically inherited alpha-proteobacterium found in a wide range of host arthropod taxa, specializes in the manipulation of host reproduction. A survey of several hundred stocks from the Bloomington Stock Center indicated that >25% are infected. An initial description of Wolbachia in a subset of these lines will be provided. Within Drosophila, Wolbachia may cause cytoplasmic incompatibility (CI), a form of post-fertilization reproductive failure. However, some stocks, although infected, do not express CI. Using a Wolbachia specific antibody and confocal microscopy, we have characterized the growth and proliferation of Wolbachia during spermatogenesis in several different host/symbiont combinations including both wild-type and mutant Drosophila lines. Considerable variation in Wolbachia density and distribution has been found in both somatic and germ cells in testes from different Drosophila lines. Regarding cyst infection, Wolbachia were found either within spermatocytes (and then spermatids) or within the somatic cyst cells surrounding the germ cells. High rates of CI are correlated with high levels of Wolbachia only when spermatocytes harbor the microbe. Wolbachia infection of somatic cyst cells, although sometimes present in very high levels, did not result in significant expression of CI. Introgression expreriments using Wolbachia strains that exhibited differing levels of CI demonstrated that CI expression is determined by Wolbachia type, but that the host genetic backgrounds influenced growth rates of Wolbachia within the testis.