Genetic Analysis of Spermatogenesis in Drosophila Hydei: Male Sterile Mutations Affecting Nuclear Development During the Primary Spermatocyte Stage

Abstract

Spermatogenesis in Drosophila has been of considerable interest since Bridges demonstrated that the Y chromosome is essential for the formation of functional spermatozoa, but completely dispensable for somatic development (Bridges, 1916). It could be shown that only six male fertility genes are located on the Y chromosome of D. melanogaster and less than 16 on the Y chromosome of D. hydei. These genes have sizes up to 1,500 kb and apparently they do not code for major protein constituents of the spermatozoa (review: Hackstein, 1987). The deletion or inactivation of a single fertility gene renders the males carrying such a mutation completely infertile, although only slight cytological effects on the germ cells can be observed. Even the deletion of the whole Y chromosome does not prevent a nearly complete terminal differentiation of the germ cells. In contrast, there exists a very large number of X chromosomal and autosomal genes which can mutate to male sterile alleles (see discussion by Hackstein, 1987). Some of these male sterile mutations cause distinct morphological phenotypes in male germ cells (Kiefer, 1983). Male sterile mutations on the X chromosome of D. melanogaster have been induced and analyzed cytologically (review: Lifschytz, 1987), but a systematic screen for male sterile mutations on the whole genome has not been performed. We therefore started a systematic screen for male sterile mutations on the X chromosome and the autosomes of D. hydei.