Ulrich Schäfer

Expression of a gene duplication encoding conserved sperm tail proteins is translationally regulated in Drosophila melanogaster.

We have analyzed a locus of Drosophila melanogaster located at 98C on chromosome 3, which contains two tandemly arranged genes, named Mst98Ca and Mst98Cb. They are two additional members of the Mst(3)CGP gene family by three criteria. (i) Both genes are exclusively transcribed in the male germ line. (ii) Both transcripts encode a protein with a high proportion of the repetitive motif Cys-Gly-Pro. (iii) Their expression is translationally controlled; while transcripts can be detected in diploid stages of spermatogenesis, association with polysomes can be shown only in haploid stages of sperm development. The genes differ markedly from the other members of the gene family in structure; they do not contain introns, they are of much larger size, and they have the Cys-Gly-Pro motifs clustered at the carboxy-terminal end of the encoded proteins. An antibody generated against the Mst98Ca protein recognizes both Mst98C proteins in D. melanogaster. In a male-sterile mutation in which spermiogenesis is blocked before individualization of sperm, both of these proteins are no longer synthesized. This finding provides proof of late translation for the Mst98C proteins and thereby independent proof of translational control of expression. Northern (RNA) and Western immunoblot analyses indicate the presence of homologous gene families in many other Drosophila species. The Mst98C proteins share sequence homology with proteins of the outer dense fibers in mammalian spermatozoa and can be localized to the sperm tail by immunofluorescence with an anti-Mst98Ca antibody.

Genes for male-specific transcripts in Drosophila melanogaster

SummaryTwelve genomic clones containing sequences complementary to male-specific trancripts were isolated from a λ library of Drosophila melanogaster. They define five gene regions which were localized by in situ hybridization at 51F, 57D, 75C, 87F, and 95F. The region at 75C contains a small gene family for a male-specific transcript whereas all other coding sequences are represented only once in the genome. Four of the male-specific RNAs accumulate in the male accessory gland while the fifth (localized at 87F) is transcribed in the male germ cells.

A newly identifiedMinute locus,M(2)32D, encodes the ribosomal protein L9 inDrosophila melanogaster

A gene encoding a ubiquitously expressed mRNA inDrosophila melanogaster was isolated and identified as the gene for ribosomal protein L9 (rpL9) by its extensive sequence homology to the corresponding gene from rat. TherpL9 gene is localized in polytene region 32D where two independent P element insertions flanking the locus are available. Remobilization of either P element generated lines with a typicalMinute phenotype, e.g. thin and short bristles, prolonged development, and female semisterility in heterozygotes as well as homozygous lethality. All these characteristics can be rescued when a 3.9 kb restriction fragment containing therpL9 gene is reintroduced by P element-mediated germline transformation. This result confirms thatM(2)32D codes for ribosomal protein L9.

The essential Drosophila melanogaster gene wds (will die slowly) codes for a WD-repeat protein with seven repeats

Abstract. We have isolated and characterized the will die slowly (wds) gene of Drosophila melanogaster, formerly known as l(1)zw8 or l(1)3Ad. The gene codes for a 2.0-kb RNA that is transcribed at all stages of development. The RNA has been localized by in situ hybridization to imaginal discs, larval brain, to nurse cells in the ovary, and to spermatogonia and spermatocytes in the testis. The putative translation product contains seven WD-repeats and is, therefore, a new member of the family of WD-proteins. Clear homologues of the Drosophila WDS protein exist in three other fully sequenced higher eukaryotes – human, Caenorhabditis elegans and Arabidopsis. A genomic fragment containing the wds transcription unit is able to rescue two different lethal wds alleles, thus proving that we have indeed isolated the wds gene.

Two separated nucleolus organizers on theDrosophila hydei Y chromosome

SummaryBy genetical, cytological, and filter saturation hybridization methods it is shown that the Y chromosome ofDrosophila hydei contains two separate nucleolus organizers, one on the short arm, the second near the tip of the long arm.

The egghead gene product influences oocyte differentiation by follicle cell-germ cell interactions in Drosophila melanogaster.

Oogenesis in Drosophila is a useful model for studying cell differentiation. We have analyzed the role of the egh gene in these processes with the aid of a newly isolated viable but female sterile allele. This mutation results in diverse variable defects in oogenesis. The most frequent defect being follicles that have either more or less than the normal number of 16 germ cells. This is caused by erroneous splitting and/or fusion of correct clusters of 16 cystocytes. The entire follicle has a rather flexible structure in this allele, most obvious by a highly variable position of the oocyte within the follicle. Moreover, a second oocyte can also develop in egh clusters. This is exclusively observed in aberrant follicles that are generated by the aforementioned splitting/fusion process. Surprisingly, even a germ cell which is distinct from the two pro-oocytes can differentiate into an oocyte under these circumstances. Hence, determination of the oocyte is definitely not fixed when germ cell clusters are enveloped by prefollicular cells, and interactions between follicle cells and germ cells must play an important role in oocyte specification. Molecular analysis proves that the oocyte-specific transcript of the egh gene is drastically reduced in this viable allele.

A new set of lacZ fusion vectors, pUCPlac, for studying gene expression in Drosophila by P-mediated transformation

A new vector, pUCPlac, was generated by introducing a truncated lacZ structural gene into pUChsneo [Steller and Pirrotta, EMBO J. 4 (1985) 167-171]. In front of this gene a new polylinker was added which will allow the in-frame fusion of sequences containing cis-acting regulatory elements plus translation start site of any given gene. After P-mediated germ-line transformation in Drosophila the action of these regulatory elements can be conveniently monitored by histochemical staining for beta-galactosidase activity. Correct cloning can be easily ascertained by supercoil plasmid sequencing of the constructs using commercially available primers.

Localization of the ribosomal RNA genes in Drosophila simulans

In situ hybridization of cloned rRNA genes from Drosophila melanogaster to D. simulans metaphase chromosomes shows that in the tested wild type strains both sex chromosomes contain a nucleolus organizer region. Silver grain counts support the published data that the X chromosomal rRNA gene number is significantly higher than the Y chromosomal.

Ribosomal DNA content and bobbed phenotype in Drosophila hydei

SummaryThe number of ribosomal RNA genes in different Drosophila hydei stocks has been determined by filter saturation hybridisation experiments. It has been shown that there is no marked correlation between the average rRNA gene number per cell in the whole animal and the bobbed phenotype when Y chromosomal nucleolar organisers are present.