Regulated processing of dec-1 eggshell proteins in Drosophila

The Drosophila dec-1 gene encodes multiple products that are necessary for proper eggshell assembly. During stages 9-12 of oogenesis the ovarian follicle cells synthesize three alternatively spliced dec-1 RNAs that encode proteins of 106, 125, and 177 kDa. All three of these primary translation products undergo developmentally regulated posttranslational cleavages. Antibodies to trpE fusion proteins containing different regions of the dec-1 proteins have been used to identify processing intermediates as well as stable derivatives of fc106, fc125, and fc177. fc106, the most abundant product of the locus, is cleaved at its N-terminus, producing an N-terminal 25-kDa derivative and s80, a stage 10 eggshell protein. During late oogenesis N-terminal cleavage of s80 yields a 20-kDa N-terminal derivative and a 60-kDa eggshell protein. fc125, which differs from fc106 by a C-terminal extension, is processed at its N-terminus through a series of transient intermediates to a stable 95-kDa C-terminal derivative in late stage 10 egg chambers. Unlike its s80 counterpart, the 95-kDa derivative is not subjected to later cleavage events. fc177, synthesized during stages 11-12, is cleaved to a stable C-terminal derivative of approximately 85 kDa. Although all of the cleavage sites fall within regions that are common to fc106, fc125, and fc177, each protein follows a different maturation pathway which results in a variety of proteins with distinctive N- and C-termini. Our data suggest that inter- or intramolecular interactions dictated by the C-terminal ends of the molecules determine the pathway followed by each dec-1 protein.

Quantification of ecdysteroids by immunoassay: comparison of enzyme immunoassay and radioimmunoassay

The performance of enzyme immunoassay (EIA) and radioimmunoassay (RIA) in the quantitative analysis of ecdysteroids was compared. The EIA was found to be at least equivalent to the RIA with respect to analytical range and sensitivity and to be more comfortable with respect to safety and time saving. When biological samples were analyzed by both assays a good correlation (r = 0.83) was found. Since the EIA has certain advantages over the RIA, we now recommend the use of the former assay for the quantification of ecdysteroids.

Immunohistological localization of regulatory peptides in the midgut of the female mosquito Aedes aegypti

The midgut of the female mosquito Aedes aegypti was studied immunohistologically with antisera to various regulatory peptides. Endocrine cells immunoreactive with antisera to perisulfakinin, RFamide, bovine pancreatic polypeptide, urotensin 1, locustatachykinin 2 and allatostatins A1 and B2 were found in the midgut. Perisulfakinin, RFamide and bovine pancreatic polypeptide all react with the same, about 500 endocrine cells, which were evenly distributed throughout the posterior midgut, with the exception of its most frontal and caudal regions. In addition, these antisera recognized three to five neurons in each ingluvial ganglion and their axons, which ran longitudinally over the anterior midgut, as well as axons innervating the pyloric sphincter. The latter axons appear to be derived from neurons located in the abdominal ganglia. Antisera to two different allatostatins recognized about 70 endocrine cells in the most caudal area of the posterior midgut and axons in the anterior midgut whose cell bodies were probably located in either the brain or the frontal ganglion. Antiserum to locustatachykinin 2 recognized endocrine cells present in the anterior midgut and the most frontal part of the posterior midgut, as well as about 50 cells in the most caudal region of the posterior midgut. Urotensin 1 immunoreactivity was found in endocrine cells in the same region as the perisulfakinin-immunoreactive cells, but no urotensin-immunoreactive axons were found in the midgut. Double labeling experiments showed that the urotensin and perisulfakinin immunoreactivities were located in different cells. Such experiments also showed that the locustatachykinin and allatostatin immunoreactivities in the most caudal area of the posterior midgut were present in different cells. No immunoreactivity was found in the mosquito midgut when using antisera to corazonin, allatropin or leucokinin IV. Since these peptides have either been isolated from, or can reasonably be expected to be present in mosquitoes, it was concluded that these peptides are not present in the mosquito midgut.

Interaction of the pelle kinase with the membrane-associated protein tube is required for transduction of the dorsoventral signal in Drosophila embryos

Within the Drosophila embryo, tube and the protein kinase pelle transduce an intracellular signal generated by the transmembrane receptor Toll. This signal directs import of the rel-related protein dorsal into ventral and ventrolateral nuclei, thereby establishing dorsoventral polarity. We show by immunolocalization that tube protein associates with the plasma membrane during interphase. We also find that tube sequences required for signaling interact with pelle in a yeast two-hybrid assay. We demonstrate that fusion of the pelle catalytic domain to the transmembrane receptor torso is sufficient to induce ventral fates; this activity is independent of Toll or tube. Lastly, we find that fusion of the tube protein to torso also induces ventral fates, but only in the presence of functional pelle. We propose a model wherein tube activates pelle by recruiting it to the plasma membrane, thereby propagating the axis-determining signal.

Abundant distribution of locustatachykinin-like peptide in the nervous system and intestine of the cockroach Leucophaea maderae

An antiserum raised to the locust neuropeptide locustatachykinin I (LomTK I) was used for analysis of the distribution of tachykinin-related peptide in the cockroach Leucophaea maderae. Extracts of dissected brains, suboesophageal ganglia, thoracic ganglia and midguts were separated by high performance liquid chromatography and the fractions analysed in enzyme-linked immunosorbent assay with use of the LomTK antiserum. Each of the tissues was found to contain LomTK-like immunoreactive (LomTK-LI) components with retention times corresponding approximately to synthetic LomTK I and II and callitachykinins I and II. The LomTK antiserum was also used for immunocytochemical mapping of peptide in the nervous system and intestine of L. maderae. A large number of LomTK-LI interneurons were detected in the proto-, deuto- and tritocerebrum of the brain and in the suboesophaegeal ganglion. The immunoreactive neurons supply processes to most parts of the brain: the central body, protocerebral bridge, mushroom body calyces, antennal lobes, optic lobe and most regions of the non-glomerular neuropil. A few protocerebral neurons send LomTK-LI processes to the glandular lobe of the corpora cardiaca. In each of the thoracic ganglia there are six LomTK-LI interneurons and in each of the unfused abdominal ones there are two interneurons. The fused terminal ganglion contains some additional cell bodies in the posterior neuromers. LomTK-LI cell bodies were detected in the frontal ganglion and fibres were seen in this ganglion as well as in the hypocerebral ganglion. The frontal ganglion supplies LomTK-LI processes to the muscle layer of the pharynx. The muscle layer of the midgut is innervated by LomTK-LI fibres from the stomatogastric system (oesophageal nerve and associated ganglia). Additionally the midgut contains numerous LomTK-LI endocrine cells. A number of the pharyngeal dilator muscles were also found to be innervated by LomTK-LI fibres, probably derived from cell bodies in the suboesophageal ganglion. All the LomTK-LI neurons of the central nervous system appear to be interneurons, suggesting a neuromodulatory role of the endogenous tachykinins. The tachykinin-like peptides from peripheral ganglia may be involved in the control of foregut and midgut contractility and possibly the peptide of the endocrine cells in the midgut has additional actions related to intestinal function.

An ecdysiostatin from flies

A bioassay for compounds with ecdysiostatic activity ('ecdysiostatins') was developed in order to prove the existence of an ecdysiostatin in blowfly larvae. The factor eluted by HPLC like Neb-TMOF (trypsin modulating oostatic factor), a hexapeptide that inhibits ecdysone biosynthesis. The ecdysiostatic activity of Neb-TMOF is specific, related peptides were less active or inactive. TMOF inhibits ecdysone biosynthesis rather than its secretion. It increases the cAMP level of ring glands. Effectors that elevate the intracellular cAMP can mimic the inhibitory effect of the ecdysiostatin. This suggests that cAMP may control steroidogenesis in fly larvae by shutting ecdysone biosynthesis. Thus, the hexapeptide acts as a prothoracicostatic hormone (PTSH) that controls ecdysone biosynthesis.

Evidence that locustatachykinin I is involved in release of adipokinetic hormone from locust corpora cardiaca

The glandular cells of the corpus cardiacum of the locust Locusta migratoria, known to synthesize and release adipokinetic hormones (AKH), are contacted by axons immunoreactive to an antiserum raised against the locust neuropeptide locustatachykinin I (LomTK I). Electron-microscopical immunocytochemistry reveals LomTK immunoreactive axon terminals, containing granular vesicles, in close contact with the glandular cells cells. Release of AKH I from isolated corpora cardiaca of the locust has been monitored in an in vitro system where the amount of AKH I released into the incubation saline is determined by reversed phase high performance liquid chromatography with fluorometric detection. We could show that LomTK I induces release of AKH from corpora cardiaca in a dose-dependent manner when tested in a range of 10-200 microM. This is thus the first clear demonstration of a substance inducing release of AKH, correlated with the presence of the substance in fibers innervating the AKH-synthesizing glandular cells, in the insect corpora cardiaca.

Characterization of the adipokinetic hormone receptor form the fat body of Manduca sexta

A tritium labeled Manduca sexta adipokinetic hormone (M-AKH) was synthesized (pE-L-T-[p3H]F-T-S-S-W-G-NH2) (specific activity 27 Ci/mmol) which was fully active in a bioassay. It was used in a filtration based binding assay to characterize the M-AKH receptor from the fat body of M. sexta. Membrane fractions were prepared from fat body and optimal binding conditions were determined. A Kd of 7.10(-10) M was determined and the receptor concentration estimated to be 0.5 pmol/mg membrane protein. No receptor binding was found when membranes were prepared from brain, heart or flight muscle of M. sexta or from fat body of the cockroach Blaberus discoidalis. However, specific binding was found with membrane preparations from the pterothoracic ganglion of M. sexta. The membranes from the ganglion had a much smaller number of binding sites than the fat body membranes, however, the binding was specific and observed in each experiment.

Biotin-containing proteins of the insect nervous system, a potential source of interference with immunocytochemical localization procedures

When the biotinylated Manduca sexta adipokinetic hormone gene was used as a probe for in situ hybridization, the intrinsic neurosecretory cells were stained with a biotin detection system that contained streptavidin or avidin. Further experiments showed that the DNA probe was not necessary for staining these cells by streptavidin-alkaline phosphatase, and that they were not stained by alkaline phosphatase alone. Similarly, the intrinsic neurosecretory cells were stained directly by streptavidin conjugated to a fluorescent dye. Other parts of the central nervous system could also be stained with streptavidin-alkaline phosphatase but not as readily as the intrinsic neurosecretory cells of the corpora cardiaca. Further analysis demonstrated three biotin-containing proteins in the intrinsic neurosecretory cells of the corpora cardiaca and in the brain. The most abundant of these proteins, when analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis, was found to have a molecular weight of 130,000, which is the size of the subunits of pyruvate carboxylase, a biotin-containing enzyme. The same protein was recognized by an antiserum against an insect pyruvate carboxylase, indicating that this protein is probably pyruvate carboxylase. The results reported here indicate that the intrinsic neurosecretory cells of the corpora cardiaca may contain pyruvate carboxylase in a concentration higher that other cells of the central nervous system. We also note that caution is necessary to avoid false positive results if an avidin containing detection system is used for in situ hybridization or immunocytochemistry.

A sapecin homologue of Holotrichia diomphalia: purification, sequencing and determination of disulfide pairs

We purified and characterized a sapecin homologue, named holotricin 1, from the hemolymph of immunized larvae of a coleopteran insect, Holotrichia diomphalia. We determined its complete amino acid sequence and three disulfide pairs. Holotricin 1 consisted of 43 amino acid residues and showed potent antibacterial activity against gram-positive bacteria, but antibacterial activity against gram-negative bacteria was not obvious.

Sterol metabolism in the tobacco hornworm, Manduca sexta--a review

A number of intermediates involved in the dealkylation and conversion of the major C28 and C29 phytosterols to cholesterol in insects were first isolated and identified in studies with the tobacco hornworm, Manduca sexta, carried out in our laboratory. We also investigated the effects of a variety of known sterol metabolism inhibitors in Manduca, particularly those affecting the delta 24-sterol reductase enzyme, and synthesized and tested a number of new inhibitors as well. In-depth studies of ecdysteroids in Manduca during embryogenesis and during pupal-adult development provided new information on molting hormone content, biosynthesis, and metabolism. In addition, this insect has been utilized in the study of three specific enzyme systems of ecdysteroid metabolism, namely 20-monooxygenase, 3-epimerase, and phosphotransferase, which are critical to activation and deactivation of molting hormones in insects.

Targeted expression of tetanus toxin light chain in Drosophila specifically eliminates synaptic transmission and causes behavioral defects

Tetanus toxin cleaves the synaptic vesicle protein synaptobrevin, and the ensuing loss of neurotransmitter exocytosis has implicated synaptobrevin in this process. To further the study of synaptic function in a genetically tractable organism and to generate a tool to disable neuronal communication for behavioural studies, we have expressed a gene encoding tetanus toxin light chain in Drosophila. Toxin expression in embryonic neurons removes detectable synaptobrevin and eliminates evoked, but not spontaneous, synaptic vesicle release. No other developmental or morphological defects are detected. Correspondingly, only synaptobrevin (n-syb), but not the ubiquitously expressed syb protein, is cleaved by tetanus toxin in vitro. Targeted expression of toxin can produce specific behavioral defects; in one case, the olfactory escape response is reduced.

The ovarian tumor protein isoforms of Drosophila melanogaster exhibit differences in function, expression, and localization

The Drosophila melanogaster ovarian tumor (otu) gene, required for normal proliferation and differentiation of the female germ-line, encodes two cytoplasmic protein isoforms, 98 and 104 kDa. Mutants with defects in this gene are typically grouped into one of three phenotypic classes: quiescent (germ cells do not proliferate), oncogenic or tumorous (germ-line cells proliferate uncontrollably), and differentiated (germ-line cells initiate but do not complete differentiation). Analysis of transformants expressing only one of the otu isoforms showed that the 104-kDa isoform (otu-104) can rescue all classes of otu mutants, whereas only differentiated mutants are rescued to a significant extent by the 98-kDa isoform (otu-98). Western analysis of protein extracts prepared from ovaries of various developmental stages indicated that otu-104 predominates in predifferentiated stages, while otu-98 is prevalent in differentiated egg chambers. Immunolocalization experiments demonstrated that otu protein is present in the cytoplasm of oogonial stem cells that populate third instar larvae and in all germ-line-derived cells until late in oogenesis. In stage 10 egg chambers, otu protein shifts to the subcortical region of nurse cells. This type of analysis also showed that upon formation of a 16-cell syncytium otu-104, but not otu-98, preferentially accumulates in the developing oocyte cytoplasm. The otu mutant protein does not show this pattern of enhanced accumulation, nor does it occur in ovaries of egalitarian and Bicaudal-D mutants, which are defective in oocyte determination. Thus, these studies indicate that the 104-kDa isoform is required for normal proliferation of female germline cells and perhaps for oocyte differentiation. The 98-kDa isoform appears to be dispensable but can provide an otu function needed for the completion of oocyte maturation.

Characterization of a spectrophotometric assay for juvenile hormone esterase

Two surrogate substrates, methyl 1-heptylthioacetothioate (HEPTAT) and methyl 1-hexylthioacetothioate (HEXTAT) were utilized to compare a new spectrophotometric assay with the standard radiochemical partition assay used to quantify juvenile hormone esterase (JHE) activity. The surrogate substrates were made with one common factor being a thiol ester moiety substituting for the ester moiety found in juvenile hormones (JHs) and a thioether replacing the 2,3-olefin of the JHs. As a result, nucleophilic attack by the serine residue of JHE at the carbonyl functional group results in a hydrolytic reaction and release of methanethiol. In the presence of Ellman's Reagent (DTNB) methanethiol will cleave the disulfide bond of DTNB resulting in a chromophore detectable at 405 nm. Methyl 1-hexylthioacetothioate and its oxygen ester analogue, methyl-1-hexylthioacetate, were compared for JHE activity. Statistical analysis of the slopes indicated a very small but significant difference between the hydrolytic rates for the thiol ester and oxygen ester. However, the data indicate that thiol esters can replace oxygen esters to quantify hydrolytic activity by the JHEs examined. Results gathered from different preparations of JHE including tissue culture media from a baculovirus expression system, affinity- and DEAE-purified enzyme, as well as insect hemolymph indicate an excellent correlation between the two assays. Isoelectric focusing of pure and crude JHE preparations resulted in coinciding peaks of hydrolytic activity when using the standard partition assay and the spectrophotometric assay, with no other peaks of activity found in the crude preparations with either substrate. Several esterase bands were found at different isoelectric points when gels were stained with alpha-naphthyl acetate.(ABSTRACT TRUNCATED AT 250 WORDS)

Cellular colocalization of diuretic peptides in locusts: a potent control mechanism

Locust abdominal ganglia are shown to colocalize Locusta-diuretic peptide-, leucokinin I-, and lysine vasopressin-like immunoreactivity in posterior lateral neurosecretory cells. Extracts of abdominal ganglia were partially purified by RP-HPLC then dot immunoassay screened with the same antisera used for immunocytochemistry. Locusta-diuretic peptide-like immunoreactive material coeluted with synthetic Locusta-diuretic peptide, and leucokinin-like immunoreactive material coeluted with locustakinin. Lysine vasopressin-like material eluted in fractions that also showed Locusta-diuretic peptide and leucokinin I immunoreactivity. The diuretic activity of synthetic Locusta-diuretic peptide and locustakinin is demonstrated, and they are shown to act at least additively to promote Malpighian tubule fluid secretion. The immunoreactive neurosecretory cells are assumed to express at least these two peptides, and a model for promoting fluid secretion is proposed.

The Drosophila lethal(2)giant larvae tumor suppressor protein is a component of the cytoskeleton

Tumor suppressor genes act as recessive determinants of cancer. In Drosophila these genes play a role in normal development and are essential for regulating cell growth and differentiation. Mutations in the gene, lethal(2)giant larvae, l(2)gl, besides causing malignant tumors in the brain and imaginal discs, generate developmental defects in a number of other tissues. Much of the uncertainty regarding the function of the l(2)gl gene product, p127, results from a lack of knowledge as to the precise location of this protein in the cell. We have investigated the cellular and subcellular localization of p127, using confocal and electron microscopy as well as biochemical and cell fractionation procedures. Our analyses indicate that p127 is located entirely within the cell in both the cytoplasm and bound to the inner face of lateral cell membranes in regions of cell junctions. On the membrane, p127 can form large aggregates which are resistant to solubilization by nonionic detergents, indicating that p127 is participating in a cytoskeletal matrix. These findings suggest that the changes in cell shape and the loss of apical-basal polarity observed in tumorous tissues are a direct result of alterations in the cytoskeleton organization caused by l(2)gl inactivation and also suggest that p127 is involved in a cytoskeletal-based intercellular communication system directing cell differentiation.

The Drosophila tumor suppressor gene dlg is required for normal synaptic bouton structure

The Drosophila tumor suppressor gene lethal (1) discs large (dlg) encodes a protein necessary for normal cell growth in epithelial and brain tissue. It shares high sequence identity to the mammalian synaptic proteins PSD-95 and SAP-70, whose functions are unknown. To determine the localization and role of dlg at synapses, we investigated its distribution and the effects of dlg mutations on Drosophila neuromuscular junctions. We show that dlg immunoreactivity is expressed at one type of glutamatergic synapse and is associated with both presynaptic and postsynaptic membranes. Mutations in dlg alter the expression of dlg and cause striking changes in the structure of the subsynaptic reticulum, a postsynaptic specialization at these synapses. These results indicate that dlg is required for normal synaptic structure and offer insights regarding the role of dlg homologs at vertebrate synapses.

Restricted occurrence of Locusta migratoria ovary maturing parsin in the brain-corpora cardiaca complex of various insect species

Ovary maturing parsin (OMP) is a gonadotrophic molecule previously isolated from the neurosecretory lobes of the corpora cardiaca of Locusta migratoria (acridian Orthoptera). A polyclonal antiserum directed against the two biologically active domains of the L. migratoria (Lom) OMP was used to investigate the occurrence of Lom OMP-like substances in brain-corpora cardiaca complexes of other insect species. Using immunohistochemistry, specimens of 40 different insect species belonging to 13 insect orders were tested. The Lom OMP-like substance was strictly limited to specimens of insect species belonging to the Acridae. It occurred in non-basophilic cells of the pars intercerebralis that project to the corpora cardiaca, as in Locusta. Although the antiserum only detected Lom OMP-like material in the Acridae, it is possible that related molecules exist in other insects. The antiserum may be very specific for domains of the Lom OMP molecule that have not been highly conserved during evolution or possibly these domains are not accessible to the antiserum in other insects.

Dosage compensation in Drosophila: the X-chromosomal binding of MSL-1 and MLE is dependent on Sxl activity

In Drosophila, dosage compensation, i.e. the equalization of levels of X-linked gene products in the two sexes, is achieved by the hypertranscription of most X-linked genes in males relative to females. The products of at least four genes, collectively termed male-specific lethal (msl) genes, are required for this process and, at least in the case of three of them, mediate this function through an association with the X chromosome in males. We have studied some of the parameters that affect the association of the msl-1 gene product and found that its presence is dependent on the wild-type function of the other three genes, leading to the conclusion that these gene products contribute to the formation of a multi-subunit complex. Furthermore, the X-chromosomal association of the msl-1 and mle gene products is negatively correlated with the level of function of the master regulatory gene Sxl and can assume either a mosaic or a uniform distribution in the tissues of mutant XX individuals. Surprisingly, we also found that the association of these two msl gene products with the two X chromosomes in females of certain mutant genotypes does not result in the hypertranscription of X-linked genes or in any apparent reduction in viability.

Coordinate regulation of downstream genes by extradenticle and the homeotic selector proteins

Mutations in the Drosophila gene extradenticle (exd), a homologue of the human proto-oncogene pbx1, cause homeotic transformations by altering the morphological consequences of homeotic selector gene activity. exd has been proposed to act by contributing to the specificity of selector homeodomain proteins for their downstream targets. Here we show that exd is indeed required for the appropriate regulation of at least some of these target genes. Expression patterns of wingless, teashirt and decapentaplegic (dpp) are altered in the embryonic midgut of embryos lacking exd, while the expression of their respective regulators (abd-A, Antp and Ubx) remains normal. Co-regulation of dpp by exd and Ubx was investigated in greater detail by examining the expression of reporter constructs in exd embryos. These experiments not only define dpp regulatory regions responsive to exd, but also distinguish two functions of exd in the regulation of dpp. exd acts with Ubx to activate dpp expression in parasegment 7 (PS7), via a minimal visceral mesoderm enhancer, and exd represses dpp expression anterior to PS7. We show that even when Ubx is ubiquitously expressed at high levels in exd embryos, Ubx is incapable of activating dpp enhancer expression. Thus, exd is an indispensable component in target gene regulation by the homeotic selector proteins.

Saliva of Lutzomyia longipalpis sibling species differs in its composition and capacity to enhance leishmaniasis

Leishmania donovani chagasi parasites, transmitted by sandflies of the Lutzomyia longipalpis species complex, normally cause visceral leishmaniasis. However, in Central America infections frequently result in cutaneous disease. We undertook experiments to investigate the possible influence of sandfly saliva on the course of infection. Erythemas caused by feeding sandflies correlated well with the levels of the erythema-inducing peptide, maxadilan, in their saliva. Saliva of Brazilian flies was the most potent, that of Colombian flies less so, and Costa Rican saliva had very little maxadilan and lacked activity. Nucleotide sequence differences in the maxadilan gene of the three species were detected by 'single strand conformational polymorphism' electrophoresis. Leishmania infections proliferated fastest when coinjected with the saliva of Costa Rican flies. Brazilian flies had less influence, and Colombian flies only a slight effect. Thus Costa Rican Lutzomyia longipalpis, vectors of non-ulcerative cutaneous disease, have very low vasodilatory activity and very little maxadilan, but their saliva strongly enhances cutaneous proliferation of Leishmania infections. Conversely, flies from Colombia and Brazil, vectors of visceral disease, have more maxadilan, but exacerbate cutaneous infections to a lesser degree. These coincidental observations suggest that species of Lutzomyia longipalpis differ in their propensity to modulate the pathology of the disease they transmit.

Diapause-dependent changes in prothoracicotropic hormone-producing neurons of the tobacco hornworm, Manduca sexta

The prothoracicotropic hormone (PTTH), which stimulates ecdysteroid synthesis in the prothoracic glands, is produced, in the dorso-lateral protocerebrum of Manduca sexta, by paired peptidergic neurons, the lateral neurosecretory cell group III (L-NSC III). Our study revealed ultrastructural features of L-NSC III, identified by immunogold labeling, and compared developing and diapause states. In developing and early-diapause pupae, L-NSC III soma ultrastructure is similar and is characterized by numerous clusters of neurosecretory granules (NSG) and an extensive trophospongium formed by satellite-glial cells. However, as diapause progresses, the ultrastructure changes, with the NSG becoming concentrated into large clusters separated by highly organized rough endoplasmic reticulum. Most conspicuous is a substantial reduction in the number of Golgi complexes and the glial trophospongium, and the presence of stacked plasma membrane separating the glia and neuron somata. The deep-diapause soma also has abundant glycogen deposits and autophagic vacuoles. With diapause termination, this morphology reverts to the nondiapause ultrastructure within three days, i.e. just before PTTH release that evokes development to the adult. During PTTH release the abundance of NSG in the soma does not change, suggesting that NSG depletion in the perikarya is not a marker for neurosecretion by the L-NSC III.

Genomic regions regulating early embryonic expression of the Drosophila neurogenic gene Delta

To identify genomic regions required for transcriptional regulation of Delta during early embryogenesis, constructs carrying promoter and gene fusions to the lacZ gene were used for germ line transformation. Most cis-regulatory sequences are dispersed throughout 6.6 kb of genomic DNA, 5' of the transcription start site; the first intron contains an enhancer element that increases the amount of RNA produced in several organs. A region was defined which drives Delta-lacZ RNA expression in clusters of neuroectodermal cells preceding and during SI neuroblast segregation. This pattern is regulated by genes of the AS-C (achaete-scute complex). To identify regulatory regions necessary for normal function of Delta during neural-epidermal lineage segregation, five minigenes consisting of fragments of the 5' genomic DNA fused to a cDNA encoding the entire protein sequence were tested for their ability to rescue the neural hyperplasia caused by a deletion of the Delta locus. Regulatory sequences required for this function are differentially distributed throughout 9 kb of genomic DNA upstream of the transcription start site. The possible significance of these findings with respect to the function of Delta during lineage segregation is discussed.

The nullo protein is a component of the actin-myosin network that mediates cellularization in Drosophila melanogaster embryos

After the 13th nuclear division cycle of Drosophila embryogenesis, cortical microfilaments are reorganized into a hexagonal network that drives the subsequent cellularization of the syncytial embryo. Zygotic transcription of the nullo and serendipity-alpha genes is required for normal structuring of the microfilament network. When either gene is deleted, the network assumes an irregular configuration leading to the formation of multinucleate cells. To investigate the role of these genes during cellularization, we have made monoclonal antibodies to both proteins. The nullo protein is present from cycle 13 through the end of cellularization. During cycle 13, it localizes between interphase actin caps and within metaphase furrows. In cellularizing embryos, nullo co-localizes with the actin-myosin network and invaginates along with the leading edge of the plasma membrane. The serendipity-alpha (sry-alpha) protein co-localizes with nullo protein to the hexagonal network but, unlike the nullo protein, it localizes to the sides rather than the vertices of each hexagon. Mutant embryos demonstrate that neither protein translationally regulates the other, but the localization of the sry-alpha protein to the hexagonal network is dependent upon nullo.

Immunogold detection of two neurohormones: the locust ovary maturing parsin and neuroparsin

The cellular localization of two neurohormones of the locust pars intercerebralis-corpora cardiaca system: the ovary maturing parsin and neuroparsin, was investigated using electron microscopic immunocytochemistry (post-embedding immunogold labelling). The ovary maturing parsin and neuroparsin containing cells were first identified in semithin sections treated by combined histochemical- and immunostaining. The neuroparsin cells were paraldehyde fuchsin positive (A-type cells) and the ovary maturing parsin cells were paraldehyde fuchsin negative when semithin sections were stained with paraldehyde fuchsin and immunostained with anti-ovary maturing parsin serum. The ovary maturing parsin and neuroparsin producing cells were identified on immunogold labelled ultrathin sections adjacent to double stained semithin sections. Ovary maturing parsin cells have larger more numerous vesicles of greater electron density than neuroparsin cells. The neuroparsin cells contained more lysosomal structures than the ovary maturing parsin cells suggesting different neurosecretory dynamics. Thus, immunogold labelling with antisera specific for each neurohormone demonstrates the individual nature of these two neurosecretory cells in the pars intercerebralis of the Locust.