The Drosophila hydei gene Dhmst101(1) encodes a testis-specific, repetitive, axoneme-associated protein with differential abundance in Y chromosomal deletion mutant flies.

To understand the effect of the megabase-sized, Y chromosomal fertility genes on different stages of spermatogenesis in Drosophila hydei, an immunoscreening was performed to search for testis-specific protein-encoding cDNAs. The array of isolated clones contained cDNA sequences derived from a gene on chromosome 5 at 101BC. The gene, Dhmst101(1), is a member of a small gene family and is specifically expressed in adult testis tissue. The mRNA encodes a protein of 344 amino acids with a deduced apparent molecular weight of 37,793 Da. The main portion of the protein sequence comprises repetitive, highly charged amino acid units and shows repeat number variations among several D. hydei laboratory stocks. Immunocytochemistry with antibodies raised against synthetic peptides localized the protein product in elongated spermatids. This pattern of expression and the evaluation of biophysical considerations on the protein sequence data suggest that the Dhmst101(1) gene product may have some importance for the structural integrity of the sperm tail. Moreover, Y chromosomal deletions affecting correct spermiogenesis lead to degradation of the Dhmst101(1) gene product.