12-Insect%20hormones[1] - Hormones in insects Pupariation...

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1 Hormones in insects Pupariation of gypsy moth (Kopec, 1917) Ligated late during instar Ligated early during instar
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2 Processes controled by hormones • Reproduction Reproduction • Development and growth • Energy metabolism • Water and ion balance •e t c . = similar to situation in vertebrates! similar to situation in vertebrates! Endocrine glands of insects • Central nervous system Central nervous system • Glandular part of corpora cardiaca • Corpora allata • Intestine • Gonads Epitracheal glands (Inka cells • Epitracheal glands (Inka cells)
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3 br = brain PI (pars intercerebralis) and PL (pars lateralis) of protocerebrum PL retrocerebral complex: cc = corpora cardiaca ca = corpora allata ptg = prothoracic gland ncc = nervus corpora cardiaca sns = stomatogastric nervous system bv = dorsal blood vessel vnc = ventral nerve cord
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4 Ring gland in Drosophila surrounding the anterior tip of the dorsal blood vessel Types of hormones • Steroid hormones Steroid hormones: ecdysteroids • Sesquiterpenes: juvenile hormones • Peptide hormones: prothoracicotropic hormone, adipokinetic hormone, hypertrehalosemic hormone, etc. ..
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5 I. Hormones and development “old” diagram of insect metamorphosis
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6 Ecdysteroids Produced in prothoracic glands (ectodermal • Produced in prothoracic glands (ectodermal origin) but also in gonads • Precursors sterols: cholesterol (animal diet) or campesterol & -sitosterol (vegetal diet) Most important ecdysteroids • Most important ecdysteroids: - ecdysone (prohormone?) - 20-hydroxyecdysone
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7 Conversion occurs in different peripheral tissues
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8 • Major role: stimulation of ecdysis by activation or stimulation of ecdysis by activation or inactivation of specific genes • Act via binding to nuclear receptors: - EcR-A, EcR-B1, EcR-B2 - EcRs form heterodimers with USP (= ultraspiracle, homolog of vertebrate ( ultraspiracle, homolog of vertebrate receptor RXR) • Diversity in tissue response result of differences in type and amount of EcR expressed
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9 Prothoracicotropic hormone • Stimulates ecdysone production in prothoracic glands • First insect hormone identified, “brain hormone” • Produced in lateral neurosecretory cells of the brain & released in corpora cardiaca • “big” PTTH (14-29 kDa) and “small” PTTH (3-7 kDa), big form = real PTTH • Active form is homodimer, binds to GPCR • In some insects ecdysone production is inhibited by ecdysiostatic hormone from brain
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10 AA structure of one chain in the PTTH homodimer of Bombyx mori Juvenile hormones Produced in corpora allata (ectodermal origin • Produced in corpora allata (ectodermal origin) • Ether derivatives of polyunsaturated fatty acids • Six major forms identified 16-19 carbon skeleton • Insect species may have one or several forms f JH JH III id d t i iti of JH, JH III considered most primitive • Several hydroxy-JH are produced which may have increased biological activity
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11 Most primitive one
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12 Major role: modify action of ecdysteroids • Major role: modify action of ecdysteroids
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This note was uploaded on 10/11/2011 for the course BIOLOGY G0G49A taught by Professor V.darras during the Fall '11 term at Katholieke Universiteit Leuven.

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12-Insect%20hormones[1] - Hormones in insects Pupariation...

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