Oöstatic hormone production in houseflies, Musca domestica, with developing ovaries

Cloning and Characterization of Aedes aegypti Trypsin Modulating Oostatic Factor (TMOF) Gut Receptor

Trypsin Modulating Oostatic Factor (TMOF) receptor was solubilized from the guts of female Ae. Aegypti and cross linked to His₆-TMOF and purified by Ni affinity chromatography. SDS PAGE identified two protein bands (45 and 61 kDa). The bands were cut digested and analyzed using MS/MS identifying a protein sequence (1306 amino acids) in the genome of Ae. aegypti. The mRNA of the receptor was extracted, the cDNA sequenced and cloned into pTAC-MAT-2. E. coli SbmA⁻ was transformed with the recombinant plasmid and the receptor was expressed in the inner membrane of the bacterial cell. The binding kinetics of TMOF-FITC was then followed showing that the cloned receptor exhibits high affinity to TMOF (K_D = 113.7 ± 18 nM ± SEM and B_max = 28.7 ± 1.8 pmol ± SEM). Incubation of TMOF-FITC with E. coli cells that express the receptor show that the receptor binds TMOF and imports it into the bacterial cells, indicating that in mosquitoes the receptor imports TMOF into the gut epithelial cells. A 3D modeling of the receptor indicates that the receptor has ATP binding sites and TMOF transport into recombinant E. coli cells is inhibited with ATPase inhibitors Na Arsenate and Na Azide.

Biochemical and Molecular Characterization of Pichia pastoris Cells Expressing Multiple TMOF Genes (tmfA) for Mosquito Larval Control

Trypsin modulating oostatic factor (TMOF), a decapeptide hormone synthesized by female mosquito ovaries, ganglia and the central nervous system of Aedes aegypti, terminates trypsin biosynthesis in larvae, and blood-fed female mosquitoes. Earlier, TMOF was cloned and expressed as a single copy in Chlorella dessicata and in Saccharomyces cerevisiae cells as a potential larvicide. Here we report the use of a methylotrophic yeast cells, Pichia pastoris, that efficiently express multi copies of heterologous proteins, that are readily ingested by mosquito larvae. P. pastoris was engineered using pPICZB (Invitrogen, CA, United States), and 2 genes: gfp-tmfA and tmfA inserted between KpnI and XbaI in the multiple cloning site. The plasmid carries a strong AOXI promoter and P. pastoris KM71 and KM71H cells were transformed by homologous recombination. The synthesis of GFP-TMOF was followed using UV and clones were analyzed using southern and Northern blot analyses. Cloning tmfA into KM71H and selection on high Zeocin concentration (2.0 mg/mL) identified a clone that carried 10 copies of tmfA. A comparison between a single and high copy (10 genes) insertions using Northern blot analyses showed that a tmfA transcript was highly expressed even after 120 h. SDS-PAGE analysis of KM71 cells transformed with gfp-tmfA identified a protein band that ran at the expected M_r of 31 kDa. Enzyme Linked Immunoadsorbant Assay (ELISA) analysis of the recombinant cells showed that 1.65 × 10⁸ and 8.27 × 10⁷ cells produce 229 and 114 μM of TMOF, respectively, and caused 100% larval mortality when fed to groups of 5 larvae in 25 mL water. These results indicate that the recombinant P. pastoris cells could be used in the future in the marsh to control mosquito populations.

Oostatic peptides

Oostatic peptides are organic molecules, which influence an insect reproduction due to a regulation of the eggs development. It was proved that decapeptide-H-Tyr-Asp-Pro-Ala-Pro-Pro-Pro-Pro-Pro-Pro-OH (YDPAPPPPPP)-isolated from mosquito Aedes aegypti, inhibits trypsin activity in the midgut of the mosquito. Therefore, it was named trypsin-modulating oostatic factor (Aea-TMOF). Feeding the recombinant cells with cloned and expressed TMOF on the coat protein of tobacco mosaic virus (TMV) to mosquito larvae, caused larval mortality. The TMOF was therefore designed for usage as a new biorational insecticide against mosquito. Similarly, a hexapeptide-H-Asn-Pro-Thr-Asn-Leu-His-OH (NPTNLH)-was isolated from the grey flesh fly Neobellieria bullata. This peptide and some of its analogs inhibited trypsin-like synthesis by the midgut in female flies and was therefore entitled Neb-TMOF. Interestingly, the synthetic Aea-TMOF and mainly its C-terminus shorten analogs, including those containing D-amino acids or methylene-oxy isosteric bond, quickly and strongly inhibited the hatchability and egg development in the flesh fly N. bullata.

The variation of the amount of the neurosecretory materials in the Corpus Allatum of Pimpla turionellae L. (Hymenoptera: ichneumonidae) during oocyte maturation

The purpose of this study is to examine the effects of neurosecretory material (NSM) in Corpus Allatum (CA) of endoparasitic Pimpla turionellae L. on reproduction. For this purpose, the egg maturation of the insect and the amount of the NSM in CA of the serial section of the brain were studied. Egg maturation was determined by measuring the terminal oocyte length. In order to determine the amount of the NSM in CA the neurosecretory granules of which were stained by paraldehyde fuchsin are considered. The egg maturation of P. turionellae have performed twice. The NSM intensity in CA continued increasingly from the first day of egg development until the first oviposition days; and reached the maximum level before the second egg maturation phase. These observations showed that the NSM in CA of this insect may be related to egg development.

Trypsin-modulating oostatic factor: a potential new larvicide for mosquito control

Trypsin-modulating oostatic factor (TMOF), a mosquito decapeptide,terminates trypsin biosynthesis in the mosquito gut. The hormone is secreted from the ovary, starting 18 h after the blood meal, circulates in the hemolymph, binds to a gut receptor and stops trypsin biosynthesis by exerting a translational control on trypsin mRNA. Because of the unique primary amino acid sequence of the hormone (YDPAPPPPPP) and its stable three-dimensional conformation, TMOF is not degraded by gut proteolytic enzymes and can traverse the gut epithelial cells into the hemolymph of adults and larvae. Using this unique property, hormone fed to different species of mosquito larvae stops food digestion and causes larval mortality. To determine the shortest amino acid sequence that can bind to the gut receptor and still cause high larval mortality, 25 analogues of TMOF were synthesized and tested. The tetrapeptide(YDPA) was as effective as the decapeptide, indicating that the binding to the gut receptor is at the N-terminus of the molecule. Cloning and expressing the hormone on the coat protein of tobacco mosaic virus (TMV) in Chlorella sp. and Saccharomyces cerevisiae cells and feeding the recombinant cells to mosquito larvae caused larval mortality. These results indicate that TMOF can be used as a new biorational insecticide against mosquito larvae.

Ovarian dynamics and host use

Oviposition behavior in herbivorous and frugivorous insects and parasitoids is dynamic at the level of the individual, responding to variation in host quality and availability. Patterns of variation in egg load in response to host presence and quality suggest that ovarian development also responds to variation in the host environment. Ovarian dynamics are mediated by feedback from oviposition, by host feeding, and by sensory input from the host. The last of these mechanisms, host sensory cuing, is known to occur in three major orders and provides strong evidence that ovarian dynamics are adaptive by design. Conditions favoring host effects on ovarian development include trade-offs between egg production and either survival or dispersal, uncertainty in the host environment, and a correlation in host conditions between the time that oogenesis is initiated and the time that eggs are laid. Some host defenses block ovarian development, suggesting that ovarian dynamics in host-specific insects should be viewed from a coevolutionary perspective.

Ecdysteroidostatin from the house fly, Musca domestica

Ovaries from house flies maintained on sucrose secrete large amounts of ecdysteroid when they are cultured with ovarian ecdysteroidogenic hormone, OEH. However, ovarian ecdysteroid secretion is reduced by incubation with both OEH and the ovarian ecdysteroidostatin (OES). A partially purified OES fraction from a semi-preparative reverse phase HPLC C18 column caused a 98% inhibition of ovarian ecdysteroid secretion in vitro at a concentration of 0.8 equivalents per microliter. Ovaries can be activated to produce ecdysteroid in vivo by feeding diet containing protein to flies maintained on sucrose. Ecdysteroid secretion was inhibited when the in vivo stimulated ovaries were cultured with OES. This suggests that OES does not interfere with the OEH activation mechanism, but blocks ovarian ecdysteroid synthesis or release. Furthermore, OES inhibition is reversible and ecdysteroid secretion resumes when OES is removed. Musca OES could explain the decrease in ecdysteroid levels found in flies after mid-vitellogenesis. Both adult male and female abdomens contain OES, but OES was not transferred to females during mating. Evidence is presented that OES is not a trypsin modulating oostatic factor.

Sequencing and characterization of trypsin modulating oostatic factor (TMOF) from the ovaries of the grey fleshfly, Neobellieria (Sarcophaga) bullata

Injection of crude extracts of late vitellogenic ovaries into staged females of the grey fleshfly Neobellieria (Sarcophaga) bullata inhibited oocyte development and biosynthesis of trypsin-like enzymes in the gut. Trypsin synthesis in N. bullata is cyclic and is correlated with egg development, which is discontinuous. A trypsin modulating oostatic factor (Neb-TMOF) was purified from 10,000 vitellogenic ovaries and sequenced by mass spectrometry. Neb-TMOF is a hexapeptide (NH2-NPTNLH-COOH). Injection of the hormone at physiological concentrations (10(-9) M), inhibited trypsin-like synthesis by the midgut of liver-fed female flies, and caused a reduction of the vitellogenin concentration in the hemolymph and of oocyte growth. The role of Neb-TMOF in controlling egg development and the physiological similarities with Aedes-TMOF are discussed.

Mass spectrometry and characterization of Aedes aegypti trypsin modulating oostatic factor (TMOF) and its analogs

Trypsin modulating oostatic factor (TMOF), a decapeptide that directly inhibits the biosynthesis of trypsin- and chymotrypsin-like enzymes in epithelial cells of mosquito midgut and indirectly inhibits vitellogenesis in anautogenous females, has been sequenced by Fourier transform mass spectrometry analysis. The peptide has a primary amino acid sequence of NH2-Tyr-Asp-Pro-Ala-(Pro)6-COOH and probably exhibits left-handed helical conformation as was shown by computer stereoview simulation. The factor is metabolized very rapidly (half-life of 1.6 h) in intact mosquitoes when injected after the blood meal. Inhibition of trypsin biosynthesis was followed in ligated abdomens, which synthesize trypsin but do not metabolise TMOF. At concentrations of 3 x 10(-9) M and 6.8 x 10(-6) M, TMOF inhibited 50 and 90% of trypsin-like enzyme biosynthesis, respectively. Several analogs of varying chain lengths were synthesized and evaluated for biological activity using dose-response curves. Switching the positions of Tyr and Asp at the N-terminus reduced the activity of the hormone, indicating that the N-terminus is important for biological activity. Removal of two to five prolines at the C-terminus also reduced activity, indicating that both the N- and C-termini are important. Synthesis of trypsin-like isozyme was followed in several insect species using [1,3-3H]diisopropyl-fluorophosphate (DFP) in the presence of tosylamide-2-phenylethyl chloromethyl ketone. Marked reduction of [1,3-3H]diisopropyl-phosphoryl-trypsin-like derivatives was noted after TMOF treatment, as assessed by polyacrylamide gel electrophoresis. These results indicate that the biosynthesis of trypsin-like enzyme in mosquitoes and other insects may be regulated by sequence-related TMOFs.

Feedback Control of Juvenile Hormone Synthesis in Cockroaches: Possible Role for Ecdysterone

Inactive female corpora allata implanted into adult males become active and continue to synthesize juvenile hormone at high rates. However, when an ovary is implanted together with the corpora allata, rates of juvenile hormone synthesis decline as the oocytes complete maturation. Injections of ecdysterone mimic the effect of an implanted ovary.

Inhibition of growth in developing oocytes of the desert locust

The location of the terminal oocytes (T) in the ovary of the desert locust dictates whether the penultimate oocytes (T-1) will enter vitellogenesis -- as long as the T oocytes are retained within the ovarioles, vitellogenesis in T-1 oocytes is prevented. When the T oocytes are ovulated into the oviduct, growth of the T-1 oocytes (new T) resumes. Inhibition of vitellogenesis in T-1 oocytes is not due to low rates of JH biosynthesis since high rates of JH biosynthesis were observed in animals in which T oocytes were retained in the ovarioles.

Effect of mating on oogenesis and oviposition in the tick Argas persicus (Oken)

The initial pattern of oogenesis after a feed is similar for mated and unmated A. persicus. The peak number of mature oocytes within the females occurred on the seventh day at 30 °C. Both groups ovulated but only mated females oviposited. At the end of the first week the mature eggs of unmated females began to undergo dissociation and resorption. The early onset of this process seems to exclude the presence of unlaid eggs as a factor inhibiting ovarian maturation. Many more eggs matured within the mated than the unmated female. After oviposition, the ovaries appear as in the unfed virgin except oocytes are fewer. When the male was mated consecutively to the 7–8th virgin female, there was a decrease in the number of eggs laid. This indicates that the male factor(s) effecting oogenesis and oviposition act on a quantitative rather than an ‘all or none’ basis. To determine whether a female was effectively mated, the ampulla must be checked for sperm. The reason for this is that the spermiophore capsules may be resorbed or may lack sperm. Spermless spermiophores enhanced fecundity but did not effect oviposition. There was evidence of mechanical influence on oocyte maturation when beads were introduced into the vagina of A. persicus. An increase in the number of beads increased the number of mature oocytes. Chemical influence on oogenesis was demonstrated by injection of male gland complex into the body cavity of unmated females.