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Synthesis and Actions of Juvenile Hormones In Insect Development (MS Power…

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A morphogenetic hormone. …

A morphogenetic hormone.

Has multiple functions and a primary role of JH in insect development is to modulate ecdysone action.

Maintains the current commitment of the tissues and cells whereas ecdysone causes both predifferentiative and differentiative cellular events that are necessary for the moult.

When JH is present, a moult to a larval stage ensures.

If JH is absent at the onset of the moult, morphogenesis occurs.

Further studies and researches are still going on that can elucidate new


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  • 1. M. Phil (Zoology), 2nd SemesterRoll: BUR MP ZOO No.: 2008 / 9Registration No.: 2546 of 2008 – 2009The University of BurdwanBurdwan – 713 104West Bengal, IndiaSARAMITA DE (CHAKRAVARTI)
  • 2. Moulting and development are controlled bythree main hormones -BrainNeurosecretory cellsCorpus cardiacumCorpus allatumEARLYLARVALATERLARVA PUPA ADULTProthoracicglandEcdysoneBrainhormone (BH)Juvenilehormone(JH)LowJHNeurosecretory cells in the brain producebrain hormone (BH), which is stored inthe corpora cardiaca (singular, corpuscardiacum) until release.1BH signals its main targetorgan, the prothoracicgland, to produce thehormone ecdysone.2Ecdysone secretionfrom the prothoracicgland is episodic, witheach release stimulatinga molt.3Juvenile hormone (JH), secreted by the corpora allata,determines the result of the molt. At relatively high concen-trations of JH, ecdysone-stimulated molting producesanother larval stage. JH suppresses metamorphosis.But when levels of JH fall below a certain concentration, apupa forms at the next ecdysone-induced molt. The adultinsect emerges from the pupa.4
  • 3. What is a Juvenile Hormone?What is a Juvenile Hormone?A sesquiterpenoid molecule that –A sesquiterpenoid molecule that – Regulator of insect developmentRegulator of insect development Prevents adult differentiationPrevents adult differentiation Retains larval structuresRetains larval structures Regulates the ovarian maturationRegulates the ovarian maturation Modulates Ecdysone actionModulates Ecdysone action Key player for phase polymorphismKey player for phase polymorphism
  • 4. JH synthesized and releasedJH synthesized and releasedby -by -► Prothoracic glands stimulated by PTTHProthoracic glands stimulated by PTTH(Prothoracicotropic Hormone), which is(Prothoracicotropic Hormone), which isproduced by neurosecretory cells in the brainproduced by neurosecretory cells in the brainand released from the terminals of eitherand released from the terminals of eitherCorpora Cardiaca (CC) or Corpora AllataCorpora Cardiaca (CC) or Corpora Allata(CA).(CA).
  • 5. Isolation of Juvenile Hormones Williams (1956) found a lipid extract from theabdomen of Hyalophora cecropia males produced JHeffects in Coleoptera (Tenebrio molitor) and in Bugsand cockroaches and also in other moths.
  • 6. Chemical Characteristics ofJuvenile Hormones The chemical identification of active principle (by gaschromatography) was facilitated by the experiment onHyalophora cecropia (Williams, 1956). Chemical formula of male Hyalophora cecropia extract asMethyl – 10- epoxy – 7 ethyl – 3, 11 – dimethyl 2, 6tridecadienoate or methyl – 12, 14 – dihomo juvenate(Meyer, 1970).
  • 7. Chemical Structure of Juvenile Hormoneandits one of the Analogue (Juvabione)Juvenile hormoneJuvabione
  • 8. Juvenile Hormone content ofHyalophora cecropia during development(After Schneiderman, 1961)Stages of DevelopmentStages of Development JH content / gm fresh weightJH content / gm fresh weightcompared with adult male (in %)compared with adult male (in %)1. Unfertilized Eggs1. Unfertilized Eggs 4.304.302. 7 – days old Embryos with yolk2. 7 – days old Embryos with yolk 3.703.703. 13. 1ststinstar larvae (freshly hatched)instar larvae (freshly hatched) 6.406.404. 54. 5ththinstar larvae (mixed ages)instar larvae (mixed ages) 0.500.505. Freshly moulted pupae5. Freshly moulted pupae 0.750.756. Diapausing Pupae (1 month old)6. Diapausing Pupae (1 month old) 0.550.557. Chilled Pupae (6 months old)7. Chilled Pupae (6 months old) 0.000.008. Pupae 2 days of adult development8. Pupae 2 days of adult development 0.000.009. Pupae 11 days of adult development9. Pupae 11 days of adult development 0.000.0010. Pupae 17 days of adult development10. Pupae 17 days of adult development 0.000.0011. Pupae 20 days of adult development11. Pupae 20 days of adult development 0.500.5012. Pupae 22 days of adult development (males)12. Pupae 22 days of adult development (males) 50.0050.0013. Adult males, 2 days old13. Adult males, 2 days old 100.00100.0014. Adult females, 2 days old14. Adult females, 2 days old 3.203.20
  • 9. Observations - JH content is fairly high in unfertilized eggs,during embryonic period and in freshlyhatched larvae. JH content decreases at the end of larvaldevelopment and in pupa, disappears anddoes not reappear until just before adultemergence; in females increases slowly, butrapidly in males.
  • 10. JH Variants There are six variants of Juvenile Hormonesnamely – JH I, JH II, JH III, JH 0, iso JH 0and methyl farnesoate. JH I and JH II are the principal JHs and JHIII is traceable.
  • 11. Molecules with JH activity
  • 12. Juvenoids or JH AnaloguesJuvenoids or JH Analogues(JHa)(JHa) A number of substances having physiological activityA number of substances having physiological activitymore or less identical with that of some of insectmore or less identical with that of some of insecthormones are found in extracts of other animalhormones are found in extracts of other animaltissues and various plants.tissues and various plants. To date, over 100 synthetic Juvenoids or JHa haveTo date, over 100 synthetic Juvenoids or JHa havebeen produced.been produced. They can be used to analyze all problems of insectThey can be used to analyze all problems of insectgrowth and morphogenesis far more easily andgrowth and morphogenesis far more easily andthouroughly than by corpora allata transplantationthouroughly than by corpora allata transplantationmethod.method. They offer prospects of biological control of newThey offer prospects of biological control of newtypes.types.
  • 13. Biological activity and RF values of the authenticjuvenile hormone and the synthesized compounds *(After Dahm et al., 1968)Name of the CompoundName of the Compound Specific ActivitySpecific Activity(Tu / µg)(Tu / µg) ****RRFF******1. t, t – C1. t, t – C1212 – ethyl – ester (VI)– ethyl – ester (VI) Inactive (at 10µg / animal)Inactive (at 10µg / animal) 0.670.672. c, t – C2. c, t – C1212 – ethyl – ester– ethyl – ester Inactive (at 10µg / animal)Inactive (at 10µg / animal) 0.710.713. t, t – C3. t, t – C1515 – ketone (VIII)– ketone (VIII) 55 0.480.484. t, t, t – C4. t, t, t – C1717 – methyl – ester (IX)– methyl – ester (IX) 200200 0.670.675. t, c, t – C5. t, c, t – C1717 – methyl – ester– methyl – ester 3030 0.670.676. c, t, t – C6. c, t, t – C1717 – methyl – ester– methyl – ester 11 0.730.737. c, c, t – C7. c, c, t – C1717 – methyl – ester– methyl – ester 11 0.730.738. dl – t, t, t – 10 – epoxy – C8. dl – t, t, t – 10 – epoxy – C1717 – methyl – ester (X)– methyl – ester (X) 20002000 0.400.409. dl – t, c, t – 10 – epoxy – C9. dl – t, c, t – 10 – epoxy – C1717 – methyl – ester (XIII)– methyl – ester (XIII) 150150 0.400.4010. dl – t, c, t – 10 – epoxy – C10. dl – t, c, t – 10 – epoxy – C1717 – methyl – ester (XIV)– methyl – ester (XIV) 1010 0.410.4111. dl – c, c, t – 10 – epoxy – C11. dl – c, c, t – 10 – epoxy – C1717 – methyl – ester (XV)– methyl – ester (XV) 1010 0.410.4112. dl – t, t, t – 6 – epoxy – C12. dl – t, t, t – 6 – epoxy – C1717 – methyl – ester (XI)– methyl – ester (XI) 200200 0.440.4413. Juvenile Hormone (from13. Juvenile Hormone (from H. cecropiaH. cecropia oil)oil) 200200 0.400.40* = All compounds were obtained by gas chromatography in pure state* = All compounds were obtained by gas chromatography in pure state** = Tu / µg means Tenebrio Units per Microgram** = Tu / µg means Tenebrio Units per Microgram*** = Thin Layer Chromatography on Silica Gel G (E. Merck) activated 2 hrs. at*** = Thin Layer Chromatography on Silica Gel G (E. Merck) activated 2 hrs. at120ºC, Benzene:Ethyl acetate = 15:1120ºC, Benzene:Ethyl acetate = 15:1
  • 14. The Mevalonate Pathway (MP) and Synthesisof the Juvenile Hormones A ramified metabolic route based on reductiveA ramified metabolic route based on reductivepolymerization of acetyl – CoA.polymerization of acetyl – CoA. Final products of MP include hormonal messengers.Final products of MP include hormonal messengers. Important peculiarities in mevalonate pathway are –Important peculiarities in mevalonate pathway are –- absence of the sterol branch- absence of the sterol branch- synthesis of juvenile hormones- synthesis of juvenile hormones
  • 15. Regulation of Mevalonate PathwayRegulation of Mevalonate Pathwayand Synthesis of JHand Synthesis of JHJH itself a key regulatory element of mevalonate pathway.JH itself a key regulatory element of mevalonate pathway.Cholesterol does not regulate the Mevalonate pathway.Cholesterol does not regulate the Mevalonate pathway.A recent study onA recent study on I. piniI. pini using quantitative real time PCRusing quantitative real time PCRexamined feeding – induced changes in gene expression ofexamined feeding – induced changes in gene expression ofseven mevalonate pathway genes.seven mevalonate pathway genes.In male all these 7 genes are expressed, but in femalesIn male all these 7 genes are expressed, but in femalesonly the first 5 genes are expressed.only the first 5 genes are expressed.
  • 16. Regulation of Mevalonate PathwayRegulation of Mevalonate Pathwayand Synthesis of JHand Synthesis of JHIn insects, mevalonate pathway can beIn insects, mevalonate pathway can beinterpreted in terms of the coordinatedinterpreted in terms of the coordinatedregulation and metabolic controlregulation and metabolic controlanalysis, rather than in terms of a keyanalysis, rather than in terms of a keyregulatory step.regulatory step.
  • 17. Cellular Receptors for JHCellular Receptors for JH A 29 kDa nuclear protein, isolated from larval epidermalA 29 kDa nuclear protein, isolated from larval epidermaland fat body cells ofand fat body cells of Manduca sextaManduca sexta with high specificitywith high specificityfor binding with JH I and JH II.for binding with JH I and JH II. Another JH receptor purified from fat body cells of bothAnother JH receptor purified from fat body cells of bothadult sexes of cockroachadult sexes of cockroach Lecophaea manderaeLecophaea manderae (64 kDa(64 kDawith two subunits, each with 32 kDa).with two subunits, each with 32 kDa). Last one related to the egg production in adult than toLast one related to the egg production in adult than tothe development of immature stages and detected in thethe development of immature stages and detected in thelast instar and adult (its structure is not known yet).last instar and adult (its structure is not known yet).
  • 18. Mechanism of Action The series of successive moulting processessubdivides the post – embryonic development ininsects into several intermoult periods, or instars,during which growth and morphogenesis arepossible. This cyclical event repeated in each ofthe instars, which are strictly inter – related, areinduced and controlled by the threemetamorphosis hormones; JH is one of them[Novák, 1952].
  • 19. Actions of Juvenile Hormones onActions of Juvenile Hormones onEndocrine SystemsEndocrine Systems Larval Moult Larval – Pupal commitment Pupal Moult
  • 20. Roles of JH in embryonic developmentRoles of JH in embryonic development• JH is wiped out by JH esterases that appear with the onset of theembryonic development and then it reappears late duringembryogenesis when it is secreted by the embryonic corpora allata.• In Hemimetabola (as in Locust) presence of JH causes prematuretermination of patterning, suppression of growth, precociousdifferentiation of the nymphal stage.• In Holometabola (in Lepidoptera) there is little effect on growth anddifferentiation despite the effect of JH on blastokinesis.
  • 21. Roles of JH in DiapauseRoles of JH in Diapause In insects, diapause is triggered by environmentalcues such as temperature, day length, humidity,etc. In adult silkworms (Bombyx mori), diapause (haltof reproduction) due to the cessation of secretionof JH by corpora allata. In rice stem-borer (Chilo suppressalis) and South –Western corn-borer (Diatraea grandiosella) JHtiter in haemolynph is high during diapause.
  • 22. Molecular Actions of JuvenileMolecular Actions of JuvenileHormonesHormones Existence of two alternative enzyme systems(Wigglesworth, 1935). Stimulates succinate oxidation and that the site ofstimulation was that part of the respiratory chainbetween succinate and cytochrome – c (Stegwee,1960).
  • 23. Molecular Actions of JuvenileMolecular Actions of JuvenileHormonesHormones Coupling of DNA molecules with certainisoprenoid compounds which include many of theeffective JH analogue. Controls gene expression at the translational level(Ilan et, al, 1970). Drosophila USP (Ultraspiracle) protein binds toJH III and JH III bisepoxide with low affinity.
  • 24. Molecular Actions of JuvenileMolecular Actions of JuvenileHormonesHormones Methoprene – tolerant (Met) gene in Drosophilamutants is most interesting one that have anintercellular JH – binding protein with reducedJH – binding activity.MET protein is found in the nucleusand has a high degree of similarity to the basic helix-loop – helix Per, Arnt and Sim (PAS) domain familymembers. In actual, a JH receptor for insect development isstill elusive.
  • 25. Larval Pupal Commitment
  • 26. Regulation of CuticularMelanization Larval pigmentation is under the control of JH inmany insects, but there are not so many studies atthe molecular level. Manduca larvae have a transparent cuticle withblack markings. So, when JH is removed byallatectomy about 30 hrs before the last larvalecdysis, cuticular melanization ccurs in the newlysynthesized 5thinstar larval cuticle and can beprevented by application of JH.
  • 27. Applications of JHs and JHa(s)¶ External application of only 1µg of methylfarnesoate dichloride (one of the most activeJHa) to adult Pyrrhocoris females inhibited thedevelopment and hatching of all the eggs laid.¶ Performs important roles in caste differentiationin both termites, ants and in honeybees.¶ Discovery of two types of Entocones (JH andMHd), lead the control of harmful insects.
  • 28. Applications of JHs and JHa(s)¶ Profound effect of JH on the viability of bugEurygaster integriceps (a serious grain pest in EasternEurope) [Teplakova, 1947].¶ Topical application of JHa to last instar larvae ofBombyx mori causes prolongation of the instar and anapprox. 20% increase in the weight of both the cocoonand the pupa compared with the control [Chang et. al.,1972].¶ The greatest attention has been paid to JHa withreference to their possible utilization as entirely newtypes of insecticides.Applications of JHs and JHa(s)Applications of JHs and JHa(s)
  • 29. Applications of JHs and JHa(s)¶ Wigglesworth (1973) compared the activity of threesamples of JH preparations in 5th(last) instar nymphs ofRhodnius prolixus.> Natural (enantiomorphous – JH I) – causes 50%inhibition of adult characters in a dose of about 15 µg,> Synthetic (Racemic – JH IIa) – less active,> Synthetic (C17 – JH i.e., JH IIb) – 2/3rdsthat of thenatural JH I.Applications of JHs and JHa(s)Applications of JHs and JHa(s)
  • 30. Concluding Remarks§ A morphogenetic hormone.§ Has multiple functions and a primary role of JH in insectdevelopment is to modulate ecdysone action.§ Maintains the current commitment of the tissues and cellswhereas ecdysone causes both predifferentiative anddifferentiative cellular events that are necessary for themoult.§ When JH is present, a moult to a larval stage ensures.§ If JH is absent at the onset of the moult, morphogenesisoccurs.§ Further studies and researches are still going on that canelucidate new aspects of the action of this unique molecule.
  • 31. AcknowledgementAcknowledgement• Dr. Abhijit MazumdarDr. Abhijit Mazumdar, Reader, Department of Zoology, The University of Burdwan.• Prof. Prasanta Kumar ChaudhuriProf. Prasanta Kumar Chaudhuri, Principal Investigator and Co – ordinator, AICOPTAXProject, Ministry of Environment and Forests, Govt. of India.• Dr. Niladri HazraDr. Niladri Hazra, Reader and Head, Department of Zoology, The University of Burdwan.• All the Faculty MembersAll the Faculty Members, Department of Zoology, The University of Burdwan.• Mr. Amitava NandiMr. Amitava Nandi, Librarian of the Department of Zoology, The University of Burdwan.• Mrs. Sangita MitraMrs. Sangita Mitra, SRF Scholar, Mr. Asif Hossain and Miss Mou Nandi, Mr. Asif Hossain and Miss Mou Nandi, JRF Scholars ofthe Entomology Research Unit, The University of Burdwan.• Other ScholarsOther Scholars of Department of Zoology, The University of Burdwan.• Non – teaching staffsNon – teaching staffs andand Technical AssistantTechnical Assistant of Department of Zoology, The University ofBurdwan.• Dr. Manas MahapatraDr. Manas Mahapatra, Scientist and Director, Simultala Conservationist, an NGO working withWildlife Institute of India, Dehradun.• Entire classmatesEntire classmates of Department of Zoology, The University of Burdwan.• My husband, Mr. Chandra Kanta DeMy husband, Mr. Chandra Kanta De and my parents, parent – in lawsmy parents, parent – in laws and elder sisterelder sister.