Yolk protein synthesis in ovariectomized and genetically agametic [X87]Drosophila melanogaster

A Novel Female-Specific and Sexual Reproduction-Associated Dmrt Gene Discovered in the Stony Coral, Euphyllia ancora

Transcription factors encoded by the Dmrt gene family regulate multiple aspects of animal reproduction. Most studies investigating the Dmrt gene family were conducted in model organisms from bilateral species, with a particular emphasis on gene function in male sex determination. It is still unclear whether the E. ancora Dmrt (EaDmrt) genes found in basal metazoans such as cnidarians share similar characteristics with orthologs in other metazoans. In this study, seven full Dmrt gene transcript sequences for a gonochoric coral, Euphyllia ancora (phylum: Cnidaria; class: Anthozoa), were obtained through transcriptome data mining, RT-PCR analysis, rapid amplification of cDNA ends, and sequencing. These EaDmrts were subjected to quantitative assays measuring temporal and tissue-specific expression. Results demonstrated a unique gene expression pattern for EaDmrtE, which is enriched in female germ cells during the spawning season. Based on the phylogenetic analyses performed across the homologous Dmrt genes in metazoans, we found that the female-specific EaDmrtE gene is not related to the DM1 gene of Acropora spp. coral nor to Dmrt1 of vertebrates, which are involved in sexual reproduction, especially in sex determination (vertebrate Dmrt1). Additionally, high levels of EaDmrtE transcripts detected in unfertilized mature eggs are retained in newly formed zygotes but decrease during embryonic development. We suggest that the newly discovered gene may play a role in oogenesis and early embryogenesis as a maternal factor in corals. Therefore, the sexual reproduction-associated Dmrt gene(s) should have arisen in cnidarians and might have evolved multiple times in metazoans.

hermaphrodite and doublesex function both dependently and independently to control various aspects of sexual differentiation in Drosophila

The hermaphrodite (her) gene is necessary for sexual differentiation in Drosophila. Our characterization of her's zygotic function suggests that one set of female-specific terminal differentiation genes, the yolk protein (yp) genes, is transcriptionally activated by two separate pathways. One is a female-specific pathway, which is positively regulated by the female-specific doublesex protein (DSXF). The other is a non-sex-specific pathway, that is positively regulated by HER. The HER pathway is prevented from functioning in males by the action of the male-specific doublesex protein (DSXM). The HER and DSX pathways also function independently to control downstream target genes in the precursor cells that give rise to the vaginal teeth and dorsal anal plate of females, and the lateral anal plates of males. However, a female-specific pathway that is dependent on both DSXF and HER controls the female-specific differentiation of the foreleg bristles and tergites 5 and 6, and the male-specific differentiation of these tissues does not require the suppression of HER's function by DSXM.

Cis-regulatory sequences leading to female-specific expression of yolk protein genes 1 and 2 in the fat body of Drosophila melanogaster

The three yolk protein genes (yp) of Drosophila melanogaster are transcribed in a sex- and tissue-limited fashion. We have searched for cis-regulatory sequences in regions flanking yp1 and yp2 to identify the elements that confer female-specific expression in the fat body. One such 127 bp element has previously been identified in this region. We show here the existence of two additional regions which confer female fat body-specific expression on an Adh reporter gene and on the native yp2 gene, respectively. This suggests some redundancy in the regulation of expression of the yp genes. Computer searches for putative binding sites for the DSX protein, which regulates sex-specific expression of the yp genes, revealed several such sites in our constructs. However, the significance of these is unclear since many such sites also occur in genes which one would not expect to be regulated in a sex-specific manner (e.g. Adh, Actin 5C). We suggest that DSX acts in concert with other proteins to mediate sex- and tissue-specific expression of the yp genes.

Ecdysteroid receptors in Drosophila melanogaster adult females

Ecdysteroid receptors were identified and partially characterized from total cell extracts of whole animals and dissected tissues from Drosophila melanogaster adult females. Binding studies indicated the presence of two ecdysteroid binding components having high affinity and specificity consistent with receptors previously identified in embryos and larvae. The highest affinity binding component in 3- to 4-day females had a dissociation constant of 9.2 x 10(-10) M and a maximal binding concentration of approximately 90 pmol/g protein, with a lower affinity component having a dissociation constant of 2.94 X 10(-9) M. Receptors at similar concentrations were also observed in abdominal walls containing adult fat body, with relatively lower receptor levels observed in ovaries. These results indicate that the observed ecdysteroid hormone concentrations in adult females can account for a physiological stimulatory effect on yolk protein synthesis in adult fat body.

Sex-specific control of Drosophila melanogaster yolk protein 1 gene expression is limited to transcription

The sex of Drosophila melanogaster is determined by a hierarchy of genes. The ultimate targets of this regulatory hierarchy are the genes encoding terminal differentiation products of one sex. For one of the best-characterized target genes, that encoding female-specific yolk protein 1 (YP1), sex-specific transcriptional controls have been clearly demonstrated. In addition, sex-specific posttranscriptional controls were suggested from experiments in which YP1 RNA was induced in males with hormones. To determine whether males can efficiently process and translate a transcript which is normally found only in females, we used a non-sex-specific promoter, the hsp70 gene promoter, to drive YP1 gene transcription in germ line transformed males. The efficiency of expression of the YP1 gene at levels of RNA splicing, translation, and protein secretion in these males was compared with that in wild-type females. These experiments show that there are no sex-specific posttranscriptional controls operating to limit the production of secreted YP1 in males. Promoters containing different numbers of heat shock elements were tested for their ability to drive YP1 gene transcription in males. These results show that incompatibility between the hsp70 gene heat shock elements and the YP1 gene promoter can be overcome by increasing the amount of hsp70 gene sequence up or downstream of the TATA box. In the course of this study, two vectors useful for placing genes under heat shock regulation were constructed. One of these vectors is designed so that the heat-induced transcript produced is the "authentic" primary transcript; it should be useful for studies of posttranscriptional regulation.

Sex-specific control of Drosophila melanogaster yolk protein 1 gene expression is limited to transcription

The sex of Drosophila melanogaster is determined by a hierarchy of genes. The ultimate targets of this regulatory hierarchy are the genes encoding terminal differentiation products of one sex. For one of the best-characterized target genes, that encoding female-specific yolk protein 1 (YP1), sex-specific transcriptional controls have been clearly demonstrated. In addition, sex-specific posttranscriptional controls were suggested from experiments in which YP1 RNA was induced in males with hormones. To determine whether males can efficiently process and translate a transcript which is normally found only in females, we used a non-sex-specific promoter, the hsp70 gene promoter, to drive YP1 gene transcription in germ line transformed males. The efficiency of expression of the YP1 gene at levels of RNA splicing, translation, and protein secretion in these males was compared with that in wild-type females. These experiments show that there are no sex-specific posttranscriptional controls operating to limit the production of secreted YP1 in males. Promoters containing different numbers of heat shock elements were tested for their ability to drive YP1 gene transcription in males. These results show that incompatibility between the hsp70 gene heat shock elements and the YP1 gene promoter can be overcome by increasing the amount of hsp70 gene sequence up or downstream of the TATA box. In the course of this study, two vectors useful for placing genes under heat shock regulation were constructed. One of these vectors is designed so that the heat-induced transcript produced is the "authentic" primary transcript; it should be useful for studies of posttranscriptional regulation.

Sequences expressed sex-specifically in Drosophila melanogaster adults

To obtain probes for sex-specific gene regulation during development in D. melanogaster, sequences expressed sex-specifically in adult flies were isolated by differential cDNA hybridization screens of a genomic library. Ten clones define new sex-specifically expressed genes. The remaining three isolates correspond to previously cloned genes encoding female-specific yolk proteins and chorion proteins. The pattern of expression of these genes in sex determination mutants and in germlineless flies, as well as their tissue specificities, permitted us to distinguish transcripts whose expression is dependent on correct sexual development of the soma or the germline. One of the female transcripts is expressed in nurse cells and oocytes. Five of the male-specific sequences are expressed in the testis during spermatogenesis: the remaining one is expressed in the soma. Experiments using a temperature-sensitive allele of tra-2 show that the presence of this male-specific transcript, found only in the adult paragonia, is not affected by temperature shift of X/X; tra-2ts2 adults. This is in contrast to yolk protein genes, which require tra-2 function in the adult for their expression in the female fat body.

Maturation and aging of adult fat body and oenocytes in Drosophila as revealed by light microscopic morphometry

A morphological and cytometric analysis of the adult fat body cells and oenocytes was made on sections of abdomens from immature, mature and senescent Drosophila melanogaster of both sexes. There are about 18,000 fat body cells in abdomens of female and mature male flies. Immature and senescent males have about 12,000 and 15,000 cells, respectively. The size of the cells is almost the same for immature flies of both sexes and increases about six-fold to approximately 2600 micron2, so that mature flies of both sexes have equivalent amounts of fat body tissue. The proportions of lipid, glycogen, and background cytoplasm of fat body cells also remain relatively constant throughout adult life, but dense, proteinaceous granules are observed in cells of senescent flies. The amounts of cellular components change dramatically due to change of cell size with age; the amount of lipid shows the greatest sexual difference with about 2x more in the females at all stages studied. The oenocytes number about 6,000 in the abdomens of all but immature male flies, which have approximately 4,000. Although the cells of both sexes triple in size to about 700 micron 2, the oenocytes of males reach maximum size earlier than those of females. The major features of oenocytes appear to be dense background cytoplasm, putative lipid droplets found only in mature flies, and pigmented granules first seen in the cells of mature flies which accumulate with age to 33% of the cytoplasm. The number of cells and their anticipated capacity for protein synthesis is discussed in relation to the production of yolk protein precursors.

Isolation of germ line-dependent female-sterile mutation that affects yolk specific sequestration and chorion formation in Drosophila

Two loci on the X chromosome have been implicated in choriogenesis by in situ hybridization of poly A-containing RNA from choriogenic eggchambers to Drosophila polytene chromosomes (A.C. Spradling and A.P. Mahowald (1979). Cell 16, 589-598): 7E and 12E. At least two genes coding for major eggshell proteins map to region 7E (A.C. Spradling, M.E. Digan, A.P. Mahowald, M. Scott, and E.A. Craig (1980). Cell 19, 905-914). In an effort to elucidate the functional role of the 12E gene product, 3600 EMS-treated X chromosomes were screened for recessive female-sterile mutations that mapped within the region 11F10-12F1. Four independent female-sterile mutations were recovered, three of which fell into one complementation group (fs29, fs117, and fs445). Mapping by analysis of recombinant progeny as well as of trans heterozygotes utilizing other deficiency chromosomes showed that the three noncomplementing mutations all mapped to region 12E1-12F1. Studies comparing chorion morphology and protein synthesis indicate localized perturbations in the extracellular assembly of eggshell components in mutant eggchambers. The germ line dependence of the mutations was established using germ line mosaics constructed by pole cell transplantation. Analysis of eggchamber protein accumulation patterns showed reduced amounts of yolk polypeptides (YPs) in the mutants. The elevated concentrations of YPs found in mutant hemolymph coupled with the normal YP biosynthetic patterns and active uptake of trypan blue by mutant oocytes suggest that 12E sequences play a role in yolk-specific sequestration.