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PubMed1996

Cosmic influences on the expression of a specific gene in the Colorado potato beetle: the diapause protein 1 gene.

Diapause protein 1 from the Colorado potato beetle, Leptinotarsa decemlineata, belongs to the family of insect storage hexamers. The protein accumulates in the hemolymph of last instar larvae and in adults reared under short-day (diapause-inducing) conditions. The protein disappears during metamorphosis, but remains in the hemolymph during diapause. The gene which encodes diapause protein 1 encompasses about 9 kb of chromosomal DNA and is composed of 5 exons, separated by 4 introns. The gene is expressed in last-instar larvae and in adults reared under short-day conditions. The messenger RNA for diapause protein 1 occurs only in the fat body. Gene expression is higher in the fat body from short-day adults than from last-instar larvae. Transcription is suppressed after topical application of pyriproxyfen, a JH-analog. The messenger RNA of the protein (approximately 2.3 kb) contains genetic information of a pre-protein of 702 amino acids, including a signal peptide of 17 amino acids and protein of 685 residues. The function of diapause protein 1 is unknown, but it is utilized during post-diapause development, probably for regeneration of the flight muscles.

Animals↗
PubMed1996

Methionine-rich hexamerin and arylphorin as precursor reservoirs for reproduction and metamorphosis in female luna moths.

The storage proteins of Lepidoptera include a pair of methionine-rich hexamerins (MtH) that are more abundant in female pupae than in males. Their inferred support of female reproduction could be achieved either by enhancing general pools of amino acids, or by hydrolyzing MtH at times and/or sites that direct its constituents to the synthesis of egg proteins. The two models were tested in Actias luna, a saturniid moth that makes its eggs during adult development. MtH and arylphorin (ArH), the third major storage protein of this species, were labeled metabolically with [35S]-methionine and [3H]-leucine, and injected individually into wandering stage caterpillars. Isotope distributions at eclosion indicated that both hexamerins supported egg formation as well as adult tissue protein synthesis. In the absence of evidence for targeting, MtH appears to support egg formation in A. luna by enhancing the amino acid pools derived from ArH. Analysis of 35S labeling and of 35S/3H ratios indicated, however, that ArH is consumed over a period that extends somewhat later in adult development than MtH. Differences in timing should prove to be much greater in Lepidoptera that delay egg formation until after eclosion.

Animals↗
PubMed1999

Occurrence of ion transport peptide (ITP) and ion transport-like peptide (ITP-L) in orthopteroids.

Comparison of the sequence and biological activity of ITP-related proteins from other insects on Schistocerca hindgut will provide further understanding of ITP interaction with its receptor (ITPR) and may thus open new avenues of insect pest control if good ITPR antagonists can be developed. Using a specific bioassay (measurement of ileal Cl- transport) and Western blot analysis with antibodies raised to Schistocerca ion transport peptide (ScgITP) sequences, we demonstrate stimulatory ITP-related peptides in the corpora cardiaca (CC) of several othopteran insects (Schistocerca gregaria, Locusta migratoria, Melanoplus sanguinipes, Xanthippus corallipes, Carausius morosus, Periplaneta americana and Acheta domesticus.). For the first time, we have immunologically detected ITP in Schistocerca brain, the tissue in which ITP transcripts are found and which has some activity in the bioassay. Neither reciprocal bioassays nor immunological results reveal any differences between two locust species, Locusta and Schistocerca, which is consistent with cDNA analysis. Using Schistocerca-derived primers and the polymerase chain reaction (PCR), we show that Locusta brain contains RNA encoding for peptides with identical sequence to ScgITP and with only a single neutral amino acid change from Schistocerca ion transport-like peptide (ScgITP-L). We present evidence that ITP-L transcripts are present in at least 3 locust/grasshopper genera but have been unable to detect ITP-L peptide to date in any tissues assayed by Western blotting at a detection limit of 0.8 pmol/tissue. Results indicate high conservation of ITP structure and biological activity among these orthopteroids, in contrast to several other insect orders.

Amino Acid Sequence↗
PubMed2004

Endopeptidase activity of larval Lacanobia oleracea corpus allatum: metabolism of Manduca sexta allatostatin and allatotropin.

The degradation of synthetic Manduca sexta allatostatin (Manse-AS) and allatotropin (Manse-AT) by enzymes associated with the corpus allatum (CA) of larvae of the tomato moth, Lacanobia oleracea, was investigated using reversed-phase high performance liquid chromatography and matrix-assisted laser desorption ionisation-time of flight mass spectrometry. Manduca sexta allatostatin was metabolised by CA extract to Manse-AS5-15, Manse-AS6-15, and Manse-AS7-15, which indicates enzymic cleavage at the C-terminal side of arginine residues R3 and R5 and the N-terminal side of R5, suggesting this is due to a trypsin-like enzyme. In support of this, the same degradation products were identified after Manse-AS was incubated with trypsin, and CA enzymic activity could be inhibited up to 79% by aprotinin. Degradation of Manse-AT by CA extract was also trypsin-like, cleaving at the C-terminal side of the basic residues K3 and R11 to produce Manse-AT4-13 and Manse-AT1-11. Metabolism by trypsin produced the same deletion peptides, but the major product due to this enzyme was Manse-AT4-11. Hydrolysis of Manse-AT by CA could only be partially inhibited by high doses of aprotinin (36%), and the CA extract also cleaved Manse-AT between M8 and T9 to produce Manse-AT1-8. A trypsin-like peptidase appears to be the major enzyme present in the CA of larval L. oleracea that acts to metabolise Manse-AS and Manse-AT. In addition, an unidentified enzyme that cleaves between M and T residues degraded Manse-AT.

Animals↗
PubMed1990

Identification and molecular analysis of storage proteins from Heliothis virescens.

Three abundant storage proteins have been detected in larval and pupal hemolymph and pupal fat body of the tobacco budworm, Heliothis virescens. These polypeptides have subunit molecular weights of 74,000, 76,000, and 82,000, as determined by SDS-PAGE and exist as 450,000-Mr hexamers in their native state. A purified 82,000-Mr storage protein fraction has been obtained along with a preparation containing equivalent amounts of the 74,000-Mr and 76,000-Mr subunits, and antisera raised to each of these components have been used to document the developmental profiles of protein accumulation and synthesis by fat body. cDNA clones corresponding to each of three abundant classes of fat body mRNAs have been recovered, and at least one of these has been unambiguously demonstrated to encode the 82,000-Mr storage protein subunit. Northern blot studies with these cDNA clones revealed that the developmental accumulation of transcripts in fat body for each was consistent with the general pattern of storage protein biosynthesis, and more interestingly, that transcripts hybridizing to two of these cDNA sequences are also found in tests. These two cDNAs have also been sequenced revealing that one encodes a polypeptide similar to arylphorins, a class of storage proteins widely distributed in Insecta. The derived amino sequence of the second cDNA, corresponding to the 82,000-Mr protein, had no unusual compositional features and determination of its structural relationship to other hemolymph polypeptides awaits molecular analysis of related genes from other insects.

Amino Acid Sequence↗
PubMed1990

Synthesis and transport of storage proteins by testes in Heliothis virescens.

The synthesis of two storage protein subunits, 76,000-Mr and 82,000-Mr polypeptides, by the testes sheath has been studied in Heliothis virescens. Like fat body, which is the primary site of synthesis for the large extratesticular pool, cells of the testes sheath secrete glycosylated storage proteins assembled into hexamers. The testis sheath differed from fat body in several important respects, including the failure to synthesize an abundant (in the hemolymph) 74,000-Mr storage protein, its relatively reduced expression of the 76,000-Mr polypeptide, and the absence of resorption of storage proteins from the lumen of the testis during pupal development. Cyst cells were also shown to import actively the 82,000-Mr storage protein by pinocytosis of testicular fluid and transfer it to the developing spermatids. Unlike other cell types that sequester storage proteins in the form of cytoplasmic granules, their localization within spermatids was exclusively mitochondrial. These observations suggest that expression of the storage protein genes is regulated tissue specifically and reveal novel pathways for their transport and, perhaps, utilization and function during development.

Animals↗
PubMed1990

Isolation and characterization of bacteria-induced protein P4 from hemolymph of Manduca sexta.

Insects synthesize several types of hemolymph proteins in response to bacterial infection. The objective of this study was to characterize a 48,000 dalton hemolymph protein induced in larvae of Manduca sexta after injection of bacteria. The protein, isolated by cation exchange and gel filtration chromatography from hemolymph of larvae injected with Micrococcus lysodeikticus, was found to be a glycoprotein with pI = 8.4. The molecular weight, isoelectric point, amino acid composition, and NH2 terminal sequence of the protein are similar to bacteria-induced protein P4 from Hyalophora cecropia, and the M. sexta protein is also designated P4. The hemolymph concentration of M. sexta P4 (35 +/- 7 micrograms/ml in day 3 fifth instar larvae) increases 30- to 45-fold by 48 h after injection of bacteria, but it does not increase in response to injection of distilled water. Lower levels of induction occur after injection of peptidoglycan fragments, zymosan, and lipopolysaccharide. The properties of M. sexta P4 are very similar to those of a previously characterized M. sexta hemolymph protein known as postlarval protein, and antibodies against P4 bind to post-larval protein.

Amino Acids↗
PubMed1992

Selectivity in storage hexamerin clearing demonstrated with hemolymph transfusions between Hyalophora cecropia and Actias luna.

When Hyalophora cecropia hemolymph was injected into wandering Actias luna larvae, a methionine-rich hexamerin was selectively transferred to the host's fat body, and completely cleared from the hemolymph by the time of pupal eclosion. Donor arylphorin was 30-40% removed from the hemolymph, and riboflavin-binding hexamerin was even less completely cleared. During the pupal-adult molt, these rates were reversed: methionine-rich hexamerin disappeared no faster than bovine serum albumin, while riboflavin-binding hexamerin was rapidly and completely cleared from the hemolymph, even though A. luna hemolymph lacks a homologue of this protein; arylphorin, again, was cleared at an intermediate rate. Selective clearing of the three hexamerins occurred at similar stages in H. cecropia, their species of origin. Developmentally programmed clearing, with selectivity at least partially conserved between genera, was also demonstrated with transfused vitellogenin: in A. luna females that were forming yolk, H. cecropia vitellogenin was cleared more rapidly than bovine serum albumin; but in younger females, and in males at all stages of metamorphosis, this Mr 510,000 molecule was instead an indicator of nonselective, large protein clearing. Nonselective clearing was more complete during adult development than during pupation. It also showed signs of being more effective for small than for large proteins, insensitive to carbohydrate conjugates, and unsaturated at the protein levels used.

Animals↗
PubMed1992

Storage proteins of the larval root weevil Diaprepes abbreviatus (Coleoptera: Curculionidae): riboflavin binding and subunit isolation.

Proteins present at high concentrations in hemolymph of the larval weevil Diaprepes abbreviatus were previously shown to bind a synthetic coumarin, 7-amino-3-phenyl coumarin (coumarin-10). One of the two native proteins previously identified (protein I) is now shown to separate into two distinct bands (proteins Ia and Ib) using native gradient pore-limiting electrophoresis. The high concentration of proteins Ia, Ib, and II in larval hemolymph, their disappearance from hemolymph upon pupation, and an apparent hexameric structure shown by chemical crosslinking identify them as hexameric storage proteins (hexamerins). At least one chromatographic form of Ib isolated by anion exchange HPLC is now shown to bind riboflavin (Rb). Binding was also demonstrated by quenching of Rb fluorescence by a partially isolated mixture of the storage proteins. Lipophorin did not quench Rb fluorescence. Rb was heat-extracted from whole hemolymph and identified by its fluorescence spectra and by reverse phase HPLC with fluorescence detection. The two subunits shared by the three holoproteins have been isolated by sequential density gradient ultracentrifugation, gel permeation HPLC, and reverse phase HPLC. All three holoproteins shared the alpha subunit (M(r) 75,000), while the beta subunit (M(r) 71,000) was lacking from one of the three. Repeated passage through an anion exchange column yielded two of the three proteins (Ib and II) in homogeneous form. Chemical crosslinking with dimethylsuberimidate indicated a hexameric structure for the holoproteins. All subunits and holoproteins stained as high mannose glycoproteins when probed with biotinylated concanavalin A on PVDF membranes. The alpha subunit was high in Met, His, and Thr, and the beta subunit was high in Lys. Both were high in Pro and had approximately 16% Phe+Tyr. Sequences of the 20 N-terminal amino acid residues of each subunit showed 45-60% homology between subunits. These coleopteran proteins also showed some sequential homology but no immunological cross-reactivity with storage proteins from the lepidopterans Galleria mellonella and Heliothis virescens.

Amino Acid Sequence↗
PubMed1994

Properties and significance of a riboflavin-binding hexamerin in the hemolymph of Hyalophora cecropia.

A riboflavin-binding hexamerin isolated from pupal hemolymph of Hyalophora cecropia has a native M(r) of 510,000, subunit M(r) of 85,000, and a 5% carbohydrate content. An intrachain cross-link was confirmed in protease limit digests. Ellman titration confirmed the presence of a sulfhydryl group, which is needed for this linkage. Though Cu2+ is known to promote the linkage, heavy metals were not detected in the isolate. Heat denaturation released ligand with the absorbency, fluorescence spectra, and chromatographic behavior of riboflavin. Binding resulted in substantial quenching of the fluorescence of both the isoalloxazine in riboflavin and of aromatic groups in the apoprotein. Kinetic analysis indicated a KD of 2.5 x 10(-7) M for riboflavin, 1.3 x 10(-7) M for lumiflavin, and greater than 1 x 10(-6) M for FMN and FAD. Over four moles of flavin were bound per mole of hexamerin. The amount of riboflavin in pupal hemolymph is sufficient to occupy only 2-3 of these sites. Riboflavin is also associated with lipophorin and vitellogenin, but the molar ratios after protein isolation were low. On a standard laboratory diet, riboflavin is in great excess, but most of it is apparently excreted before the apoprotein first appears in the hemolymph, just before wandering. The concentration of riboflavin-binding hexamerin rises to 15-30 mg/ml in pupae; relative to other hexamerins, very little is stored in the fat body. All of the apoprotein and 75% of riboflavin disappear from the hemolymph during adult development. An amount of flavin at least equal to that stored in pupal hemolymph is transferred to the eggs formed during this period.

Animals↗
PubMed1995

Utilization of [14C]phenylalanine derived from arylphorin or free amino acid in Manduca sexta pharate adults.

The role of arylphorin as a storage protein was studied using 14C-arylphorin. 14C-arylphorin was produced optimally by incubating one-half fat body from Manduca sexta fifth instar larvae at 22 degrees C for 24 h, in 1 ml of medium containing amino acids at 25% of their physiological concentration with [U-14C]-phenylalanine (phe) provided initially without nonlabeled phenylalanine. Nonlabeled phe was provided after 1 h at 16% of its physiological concentration. The specific activity of 14C-arylphorin produced in vitro was 30 times greater than that generated in vivo. Injection of 14C-arylphorin into pharate adults was used to study the distribution of 14C-phe derived from this protein into 14CO2 and tissues for comparison with injection of free 14C-phe during the middle (days 6 to 12 pharate adult) and late (days 12 to 17 pharate adult) stages of adult development. Appearance of 14CO2 from 14C-arylphorin as compared to 14C-phenylalanine showed a slower time course during both the middle and late stages of development, in keeping with the time needed for degradation of the protein. In accord with faster phe turnover near the end of adult development, total 14CO2 production was greater and the retention of 14C in hemolymph and fat body was less compared to the middle stage of development regardless of whether 14C-arylphorin or 14C-phe was injected. In the middle stage of development, the appearance of 14C in the cuticle and head parts was greater, whereas incorporation into abdomen and thorax was less than during the late stage of development. Since the pattern of 14C distribution from 14C-arylphorin and 14C-phe was similar, one major function of arylphorin must be as a storage protein replenishing the supply of free amino acids used for synthesis of adult tissues. These results also suggest a limited contribution of M. sexta arylphorin to formation of the cuticle subsequent to day-6 pharate adult.

Amino Acids↗
PubMed1991

Insect antibacterial proteins: not just for insects and against bacteria.

In response to a bacterial infection, insects launch an array of countermeasures. Among these are the antibacterial proteins, which effectively lyse bacteria or are bacteriostatic. These proteins were generally assumed to be restricted to insects, yet recent information has shown some homologous counterparts in vertebrates, including humans. Recent data have revealed that at least some of these proteins can also act against eukaryotic cells, including human infectious parasites. The latter activities have opened up new possibilities for disease control.

Animals↗
PubMed2003

Role of neurosecretory cells in the photoperiodic induction of pupal diapause of the tobacco hornworm Manduca sexta.

In the tobacco hornworm, Manduca sexta, pupal diapause can be induced by exposure of fifth-instar larvae to a short-day photoperiod. We studied the effect of surgical ablation of tissues containing the neurosecretory cells of the brain of fifth-instar larvae on the photoperiodic induction of pupal diapause. At the end of the experiments, we immunostained the neurosecretory cells to determine the success of the ablations. Under long-day conditions (LD 16:8 at 22 degrees C), all intact larvae, most of the sham-operated larvae, and control-operated larvae developed into nondiapausing pupae. Under short-day conditions (LD 10:14 at 22 degrees C), most intact, sham-operated, and control-operated larvae developed into diapausing pupae. Removal of type-II cells did not interfere with the photoperiodic response. Under long-day conditions, elimination of type-Ia(1) cells did not affect the incidence of nondiapausing pupae. When type-Ia(1) cells were removed under short-day conditions, however, the incidence of nondiapausing pupae was higher (51%, n = 41) than that of the intact (16%, n = 75), sham-operated (24%, n = 88), control-operated larvae (5%, n = 40), and larvae with type-II cells removed (11%, n = 27). Thus, removal of type-Ia(1) cells can impede induction of diapause. These results indicate that the type-Ia(1) neurosecretory cells have an important role in the induction of pupal diapause.

Animals↗
PubMed1994

Locustatachykinin immunoreactivity in the blowfly central nervous system and intestine.

An antiserum raised against locustatachykinin I, one of four myotropic peptides that have been isolated from the locust brain and corpora cardiaca, was characterized by enzyme-linked immunosorbent assay (ELISA) and used for immunocytochemical detection of neurons and endocrine cells in the nervous system and intestine of the blowfly Calliphora vomitoria. The ELISA characterization indicated that the antiserum recognizes the common C-terminus sequence of the locustatachykinins I-III. Hence, the cross reaction with locustatachykinin IV is less, and in competitive ELISAs no cross reaction was detected with a series of vertebrate tachykinins tested. It was also shown that the antiserum recognized material in extracts of blowfly heads, as measured in ELISA. In high-performance liquid chromatography the extracted locustatachykinin-like immunoreactive (LomTK-LI) material eluted in two different ranges. A fairly large number of LomTK-LI neurons was detected in the blowfly brain and thoracicoabdominal ganglion. A total of about 160 LomTK-LI neurons was seen in the proto-, deuto-, and tritocerebrum and subesophageal ganglion. Immunoreactive processes from these neurons could be traced in many neuropil regions of the brain: superior and dorsomedian protocerebrum, optic tubercle, fan-shaped body and ventral bodies of the central complex, all the glomeruli of the antennal lobes, and tritocerebral and subesophageal neuropil. No immunoreactivity was seen in the mushroom bodies or the optic lobes. In the fused thoracicoabdominal ganglion, 46 LomTK-LI neurons could be resolved. The less evolved larval nervous system was also investigated to obtain additional information on the morphology and projections of immunoreactive neurons. In neither the larval nor the adult nervous systems could we identify any efferent or afferent immunoreactive axons or neurosecretory cells. The widespread distribution of LomTK-LI material in interneurons suggests an important role of the native peptide(s) as a neurotransmitter or neuromodulator within the central nervous system. Additionally a regulatory function in the intestine is indicated by the presence of immunoreactivity in endocrine cells of the midgut.

Amino Acid Sequence↗
PubMed1994

Embryonic expression of the single Tribolium engrailed homolog.

We have cloned and sequenced the single Tribolium homolog of the Drosophila engrailed gene. The predicted protein contains a homeobox and several domains conserved among all engrailed genes identified to date. In addition it contains several features specific to the invected homologs of Bombyx and Drosophila, indicating that these features most likely were present in the ancestral gene in the common ancestor of holometobolous insects. We used the cross-reacting monoclonal antibody, 4D9, to follow the expression of the Engrailed protein during segmentation in Tribolium embryos. As in other insects, Engrailed accumulates in the nuclei of cells along the posterior margin of each segment. The first Engrailed stripe appears as the embryonic rudiment condenses. Then as the rudiment elongates into a germ band, Engrailed stripes appear in an anterior to posterior progression, just prior to morphological evidence of the formation of each segment. As in Drosophila (a long germ insect), expression of engrailed in Tribolium (classified as a short germ insect) is preceded by the expression of several homologous segmentation genes, suggesting that similar genetic regulatory mechanisms are shared by diverse developmental types.

Amino Acid Sequence↗
PubMed1983

Insect immunity. Attacins, a family of antibacterial proteins from Hyalophora cecropia.

Six closely related antibacterial proteins, attacins A-F, were isolated from the hemolymph of immunized pupae of the Cecropia moth, Hyalophora cecropia. Chromatofocusing separated attacins A-F, with isoelectric points between 5.7 and 8.3. Immunological experiments show that the attacins constitute antibacterially active forms of the previously isolated inducible immune protein P5. Their mol. wts., 20-23 K, are similar to that of protein P5, but significantly lower than 28 K found for preP5 synthesized in vitro (see accompanying paper). The six attacins can be divided into two groups according to their amino acid composition and amino-terminal sequences, attacins A-D constitute a basic group and attacins E and F an acidic one. Within each group the forms are very similar. The attacins efficiently killed Escherichia coli and two other Gram-negative bacteria isolated from the gut of a silk worm but they did not act on other Gram-positive and Gram-negative bacteria tested. Only growing cells of E. coli were attacked; cells suspended in phosphate buffer were inert. Besides the cecropins and lysozyme, the attacins represent a third class of antibacterial proteins in the humoral immune system of H. cecropia.

Amino Acid Sequence↗
PubMed1983

Insect immunity. Isolation of cDNA clones corresponding to attacins and immune protein P4 from Hyalophora cecropia.

Diapausing pupae of the Cecropia moth (Hyalophora cecropia) respond to an injection of live bacteria by the selective synthesis of certain types of RNA and immune proteins (designated P1-P9). The in vitro translation products of RNA from both injured and infected pupae showed specific patterns with a defined number of extra bands. Some proteins characteristic of the normal RNA were reduced in the immune RNA translation products. Antibody reaction was used to show the selective synthesis of immune proteins P4 and P5 with mRNA from pupae subjected to injury or infection. The protein synthesized in vitro, which cross-reacted with P5 antibodies, is most likely a precursor of the attacins described in the preceding paper. A cDNA clone bank was prepared and two clones were isolated and shown to contain 750 bp corresponding to P4 and 250 bp of attacin information. These clones were used to estimate the sizes of the mRNAs by Northern blotting and to estimate, by RNA/DNA hybridization, the levels of P4 and P5 mRNA. In vivo incorporation of [35S]methionine into attacins and P4 during different conditions was compared with the levels of the corresponding mRNA.

Animals↗