The regulation of the yolk protein genes,a family of sex differentiation genes in Drosophila melanogaster

There are many obvious morphological and behavioural differences between male and female Drosophila, whose differing phenotypes are produced by a hierarchy of sex determination genes. These genes have been well characterised at the genetic and molecular level. Similarly, a number of sex-specific differentiation genes have been characterised, such as the chorion and vitelline membrane genes in females and the sex peptide and other accessory gland proteins in males. Despite the depth of these parallel studies, there is only one example of a direct link between the sex determination pathway and the downstream sex differentiation genes, namely the regulation of the female-specific yolk protein genes. The yolk proteins are synthesised in the fat body and ovarian follicle cells of the adult female and are subsequently transported to the oocyte where they are stored for utilization during embrygenesis. The expression of the yolk protein genes is not entirely controlled by the sex determination hierarchy, as several different regulatory pathways must interact to direct their correct sexual, temporal and spatial regulation during development.     

The isolation and characterization of antibiotic biosynthesis genes

Antibiotic biosynthesis pathways are found in a broad range of Gram positive prokaryotes, a smaller range of Gram negative prokaryotes and a limited range of eukaryotes. A variety of techniques can be used to identify the genes involved in the biosynthesis of these compounds ranging from genetic complementation and interspecific gene transfer to polymerase chain reaction amplification and transposon mutagenesis. The dissection of these cloned pathways and the understanding of their structure and regulation has led to insights into the structure and function of antibiotic biosynthesis genes. With new knowledge of the structural similarities and relationships between related antibiotic biosynthesis pathways, the possibility of directed manipulation of specific genes to allow synthesis of novel antibiotics is now possible.     

Presence, isolation and characterization of yolk DNA from chicken eggs

ＥｘｔｒａｏｒｄｉｎａｒｙａｍｏｕｎｔｓｏｆＤＮＡｗｅｒｅｄｅｔｅｃｔｅｄｉｎｔｈｅｏｏｃｙｔｅｓａｎｄｍａｔｕｒｅｅｇｇｓｏｆａｍｐｈｉｂｉａｎｓａｎｄａｖｅｓ[1,2].ＥａｒｌｙｓｔｕｄｉｅｓｉｎｄｉｃａｔｅｄｔｈａｔｔｈｅｓｅＤＮＡａｒｅｉｎｔｒｉｎｓｉｃｔｏｙｏｌｋｐｌａｔｅｌｅｔｓｏｒｙｏｌｋｇｒａｎｕｌｅｓ[3].Ｂｒｕｃｅ[4]ｉｓｏｌａｔｅｄＤＮＡｆｒｏｍｉｎｔｒａｃｅｌｌｕｌａｒｙｏｌｋｇｒａｎｕｌｅｓｏｆｃｈｉｃｋｅｎｅｍｂｒｙｏｓ.Ｏｕｒｐｒｅｖｉｏｕｓｓｔｕｄｉｅｓｗｅｒｅｆｏｃｕｓ…     

Evolution of yolk protein genes in the Echinodermata

Vitellogenin genes (vtg) encode large lipid transfer proteins (LLTPs) that are typically female‐specific, functioning as precursors to major yolk proteins (MYPs). Within the phylum Echinodermata, however, the MYP of the Echinozoa (Echinoidea + Holothuroidea) is expressed by an unrelated transferrin‐like gene that has a reproductive function in both sexes. We investigated egg proteins in the Asterozoa (Asteroidea + Ophiuroidea), a sister clade to the Echinozoa, showing that eggs of the asteroid Parvulastra exigua contain a vitellogenin protein (Vtg). vtg is expressed by P. exigua, a species with large eggs and nonfeeding larvae, and by the related asterinid Patiriella regularis which has small eggs and feeding larvae. In the Asteroidea, therefore, the reproductive function of vtg is conserved despite significant life history evolution. Like the echinozoan MYP gene, asteroid vtg is expressed in both sexes and may play a role in the development of both ovaries and testes. Phylogenetic analysis indicated that a putative Vtg from the sea urchin genome, a likely pseudogene, does not clade with asteroid Vtg. We propose the following sequence as a potential pathway for the evolution of YP genes in the Echinodermata: (1) the ancestral echinoderm produced YPs derived from Vtg, (2) bisexual vtg expression subsequently evolved in the echinoderm lineage, (3) the reproductive function of vtg was assumed by a transferrin‐like gene in the ancestral echinozoan, and (4) redundant echinozoan vtg was released from stabilizing selection.     

Ecdysteroids regulate yolk protein uptake by Drosophila melanogaster oocytes

Juvenile hormones (JHs) are thought to drive the regulation of yolk protein uptake by ovaries in Drosophila melanogaster. However, the level of JH production in a mutant stock (ap(56f)) is depressed yet the flies are normally vitellogenic. The production of ecdysteroids by these ap(56f) ovaries in vitro is elevated above that of wild-type ovaries. The incubation of wild-type ovaries in the presence of 0.1mM JHB(3) increased ecdysteroid biosynthesis only during the first 18h following eclosion. Female Drosophila melanogaster undergo a pre-vitellogenic reproductive diapause when exposed to low temperature (11 degrees C) and a short-day photoperiod (L12:D12). The rate of ecdysteroid synthesis by the ovaries, but not JH production, increased within 12h of a temperature upshift to 25 degrees C from a basal level of 20+/-1pg/10 pair of ovaries/5h to a sustained level of 150+/-20pg/10 pair/5h. Vitellogenic oocytes were noted in all females within 12h of this temperature upshift. Diapause was also terminated by the injection of 1&mgr;g of 20-hydroxyecdysone into the abdomens of diapausing females as determined by an increase in ovary size, and the appearance of vitellogenic oocytes as compared to controls. These results are consistent with a revised model for the regulation of yolk protein uptake by ovaries in which ecdysteroids, and not JHs, play the prominent role.     

The ribosomal protein genes and Minute loci of Drosophila melanogaster

Background

Mutations in genes encoding ribosomal proteins (RPs) have been shown to cause an array of cellular and developmental defects in a variety of organisms. In Drosophila melanogaster, disruption of RP genes can result in the 'Minute' syndrome of dominant, haploinsufficient phenotypes, which include prolonged development, short and thin bristles, and poor fertility and viability. While more than 50 Minute loci have been defined genetically, only 15 have so far been characterized molecularly and shown to correspond to RP genes.

Results

We combined bioinformatic and genetic approaches to conduct a systematic analysis of the relationship between RP genes and Minute loci. First, we identified 88 genes encoding 79 different cytoplasmic RPs (CRPs) and 75 genes encoding distinct mitochondrial RPs (MRPs). Interestingly, nine CRP genes are present as duplicates and, while all appear to be functional, one member of each gene pair has relatively limited expression. Next, we defined 65 discrete Minute loci by genetic criteria. Of these, 64 correspond to, or very likely correspond to, CRP genes; the single non-CRP-encoding Minute gene encodes a translation initiation factor subunit. Significantly, MRP genes and more than 20 CRP genes do not correspond to Minute loci.

Conclusion

This work answers a longstanding question about the molecular nature of Minute loci and suggests that Minute phenotypes arise from suboptimal protein synthesis resulting from reduced levels of cytoribosomes. Furthermore, by identifying the majority of haplolethal and haplosterile loci at the molecular level, our data will directly benefit efforts to attain complete deletion coverage of the D. melanogaster genome.     

Phosphorylation polymorphism in the yolk protein 2 of Drosophila hawaiiensis

An intraspecific polymorphism in the electrophoretic migration pattern of the yolk proteins in D. hawaiiensis was established and characterized. The polymorphism includes yolk protein migration patterns of two, three, or four bands by polyacrylamide gel electrophoresis. Peptide mapping analysis demonstrates that in the two band migration pattern YP2 comigrates with YP3, whereas in the three and four band migration patterns YP2 migrates between YP1 and YP3 in addition to comigrating with YP3. It further demonstrates that the top two bands of the four band migration pattern consists of YP1. Phosphatase treatment of the yolk proteins establishes that the different electrophoretic migration patterns of YP2 are caused by different degrees of phosphorylation. It is suggested that the YP1 polymorphism is caused by a yp1 gene modification and that the YP2 polymorphism is caused by two different post-translational processing paths.     

The nucleotide sequence of the gene coding for Drosophila melanogaster yolk protein 3

The entire sequence of the Drosophila melanogaster yolk protein 3 (YP3) gene (yp3), including 1822 nucleotides (nt) of 5'- and 834 nt of 3'-flanking DNA, has been determined. In addition, the 5' and 3' ends of the mRNA and the two introns have been mapped. The predicted amino acid sequence of YP3 has considerable homology (43%) to the other two yolk proteins of D. melanogaster. The nucleotide sequence of yp3 was compared to the other two yolk protein genes which have the same developmental pattern of expression. In addition to extensive homology between the protein coding regions, we found two small regions of homology between yp3 flanking sequences and a segment of DNA required for normal expression of the yolk protein 1 gene in adult female fat bodies.     

A microtubule-associated protein in Drosophila melanogaster: identification, characterization, and isolation of coding sequences

Microtubules and microtubule-associated proteins (MAPs) have been isolated from cultured cells of Drosophila melanogaster by a taxol-dependent polymerization procedure. The principal MAPs are a group of four polypeptides with similar electrophoretic mobilities corresponding to approximately Mr 205,000 (the 205K MAP). These proteins are resistant to precipitation by boiling. One mouse monoclonal antibody and one polyclonal rabbit antiserum specific for the Mr 205,000 MAP were produced and characterized by immunoblotting and indirect immunofluorescence. Both antibody preparations stain the Mr 205,000 molecules and an Mr 255,000 molecule in immunoblots of Drosophila cell homogenates; the rabbit antiserum also stains an Mr 150,000 triplet. Both preparations stain the microtubules of the mitotic spindle, and the rabbit antiserum stains the cytoplasmic microtubules as well. Experiments using affinity-purified rabbit antiserum demonstrate that it is the Mr 205,000 species that is located in the mitotic apparatus and on cytoplasmic microtubules. A random shear genomic library was produced in the expressing vector lambda gt11 and screened with the rabbit antiserum to isolate the DNA sequences encoding these polypeptides. Several cross-hybridizing clones were recovered, shown to encode antigenic determinants in the Mr 205,000 MAP, and characterized by hybridization to Northern blots of mRNA and Southern blots of genomic DNA. Analysis by in situ hybridization reveals that the gene encoding the 205K MAP is located in polytene region 100EF.