The Drosophila melanogaster z600 gene encodes a chromatin-associated protein synthesized in the syncytial blastoderm.

The Drosophila melanogaster z600 gene is zygotically expressed with gene transcripts accumulating transiently during early embryogenesis. Based on nucleotide sequence analysis, z600 is predicted to encode a small, basic, histone-like protein. Antibodies generated against a beta-galactosidase::z600 fusion protein immunoprecipitated the z600 in vitro translation product and detected a z600 protein present predominantly in 2- to 4-h embryos. We localized the z600 protein in whole-amount embryos by indirect immunofluorescence. These studies show that the protein is located in the nucleus and associated with chromatin in the syncytial blastoderm.

Drop out: a third chromosome maternal-effect locus required for formation of the Drosophila cellular blastoderm.

drop out (dop) is a recessive maternal-effect locus identified in a screen for female-sterile mutations in Drosophila polytene region 71C-F. Phenotypic analyses of the dop mutation indicate that the gene is required for proper formation of the cellular blastoderm. In embryos derived from either homozygous or hemizygous dop mothers, cytoplasmic clearing, nuclear migration and division, and pole cell formation appear normal. However, developmental defects are observed prior to and during cellularization of the blastoderm. At the beginning of nuclear cycle 14, the distinct separation of the internal yolk mass and the cortical cytoplasm breaks down. Subsequently, a population of somatic nuclei located at the periphery of the syncytial blastoderm becomes irregularly spaced and nonuniform in their distribution. Despite a somewhat regular formation of the cortical actin network, cellularization in mutant embryos is extremely variable. Such embryos fail to gastrulate normally and produce variable amounts of defective cuticle. Overall, our analyses suggest that the dop gene functions in maintaining the separation of yolk and cortical cytoplasm and in stabilizing the distribution of somatic nuclei in the Drosophila syncytial blastoderm.

Identification and characterization of latex-specific proteins in opium poppy.

Latex from the opium poppy, Papaver somniferum L., was analyzed by polyacrylamide gel electrophoresis (PAGE). Two latex-specific bands were identified in protein samples of poppy latex using one-dimensional native PAGE. Second dimension analysis with SDS-PAGE indicates that these proteins have a relative molecular weight of approximately 20 kilodaltons. We have termed these polypeptides the major latex proteins (MLPs). Polyclonal antibodies prepared against the MLPs were used to probe protein gel blots of latex and poppy tissues known to lack laticifers. Laticifer-free tissues showed no reaction with anti-MLP immunoglobulin G indicating that MLPs are found only in poppy latex. MLP distribution was also examined in mature opium poppy tissues by immunocytochemistry. Laticifers were differentially labeled by fluorescein isothiocyanate secondary labeling of anti-MLP immunoglobulin G and could easily be identified in both transverse and longitudinal section. Fractionation studies of isolated latex showed that MLPs are concentrated in the latex cytosol and not in alkaloidal vesicles. Analysis of latex proteins by conventional two-dimensional electrophoresis indicates that the two MLP bands are composed of several distinct polypeptides with similar relative molecular weights. The pIs of these molecules range from 6.0 to 3.5. The role(s) of MLPs in laticifer metabolism has not been determined.

Expression of the Drosophila gonadal gene: alternative promoters control the germ-line expression of monocistronic and bicistronic gene transcripts.

The Drosophila gonadal (gdl) gene is differentially expressed in the male and female germ lines. In males, expression in the gdlM mode results in a 1200-/1500-nucleotide RNA pair, whereas in females, expression in the gdlF mode results in a 1000-/1300-nucleotide RNA pair. Since the two expression modes are a result of alternative promoter usage, the sex-specific transcripts differ at their 5' ends. These sequence differences affect the coding capacity of the gene. A common open reading frame (ORF) of 193 codons (ORF193) is present in all four gdl transcripts; a consequence of the additional sequences at the 5' end of the gdlM transcripts is the presence of an additional ORF of 39 codons (ORF39). Translation of gdlF and gdlM cRNAs in a reticulocyte lysate reveals that these transcripts can serve as monocistronic and bicistronic mRNAs in vitro. An analysis of germ-line transformants harboring gdl-lacZ gene fusions provides information on gdl gene expression during gametogenesis. The fusion genes are transcribed and translated in the germ line; beta-galactosidase activity is detected in premeiotic and postmeiotic spermatogenic stages in males, and in nurse cells and oocytes of developing egg chambers in females. Both gdlM ORFs are used because transformant lines expressing the lacZ gene, fused in frame with either ORF39 or ORF193, are positive for beta-galactosidase activity in the testes. These studies also reveal that separable transcription control elements are responsible for gdl expression in the male and female germ lines.

Ets oncogene-related gene Elg functions in Drosophila oogenesis.

Members of the ets gene family encode transcription factors that regulate the expression of a variety of cellular and viral genes including several protooncogenes. We have utilized Drosophila to elucidate the in vivo function of one family member. We show by complementation rescue and sequence analysis that the female sterile mutant tiny eggs (tne) is an allele of the Drosophila Ets-related gene Elg (also called D-elg). The mutation of a highly conserved tyrosine residue in the ETS DNA-binding domain of the Elg gene product demonstrates that normal gene function is required for proper follicle cell migration, chorion formation, and nurse cell-chromosome decondensation during Drosophila oogenesis.

Endoderm-specific expression of the Drosophila mex1 gene.

The Drosophila mex1 gene is one of several genes clustered within a 10-kb interval of polytene region 71CD that includes the ecdysone-regulated Eip28/29 gene. mex1 is expressed in several developmental stages, with gene transcripts accumulating initially in 9- to 12-hr embryos. During embryogenesis, mex1 exhibits an endoderm-specific pattern of expression. mex1 transcripts are first detected in the anterior and posterior midgut primordia of stage 12 embryos; subsequently, mex1 mRNA accumulates solely in the differentiating embryonic midgut. DNA sequence analysis reveals that the mex1 gene encodes an unusual cysteine-rich polypeptide.

D-MEF2: a MADS box transcription factor expressed in differentiating mesoderm and muscle cell lineages during Drosophila embryogenesis.

The myocyte enhancer factor (MEF) 2 family of transcription factors has been implicated in the regulation of muscle transcription in vertebrates. We have cloned a protein from Drosophila, termed D-MEF2, that shares extensive amino acid homology with the MADS (MCM1, Agamous, Deficiens, and serum-response factor) domains of the vertebrate MEF2 proteins. D-mef2 gene expression is first detected during Drosophila embryogenesis within mesodermal precursor cells prior to specification of the somatic and visceral muscle lineages. Expression of D-mef2 is dependent on the mesodermal determinants twist and snail but independent of the homeobox-containing gene tinman, which is required for visceral muscle and heart development. D-mef2 expression precedes that of the MyoD homologue, nautilus, and, in contrast to nautilus, D-mef2 appears to be expressed in all somatic and visceral muscle cell precursors. Its temporal and spatial expression patterns suggest that D-mef2 may play an important role in commitment of mesoderm to myogenic lineages.