title: Locust phase polyphenism: Does epigenetic precede endocrine regulation?
abstract: The morphological, physiological and behavioural differences between solitarious and gregarious desert locusts are so pronounced that one could easily mistake the two phases as belonging to different species, if one has no knowledge of the phenomenon of phenotypic plasticity. A number of phase-specific features are hormonally controlled. Juvenile hormone promotes several solitarious features, the green cuticular colour being the most obvious one. The neuropeptide corazonin elicits the dark cuticular colour that is typical for the gregarious phase, as well as particular gregarious behavioural characteristics. However, it had to be concluded, for multiple reasons, that the endocrine system is not the primary phase-determining system. Our observation that longevity gets imprinted in very early life by crowding of the young hatchlings, and that it cannot be changed thereafter, made us consider the possibility that, perhaps, epigenetic control of gene expression might be, if not the missing, a primary phase-determining mechanism. Imprinting is likely to involve DNA methylation and histone modification. Analysis of a Schistocerca EST database of nervous tissue identified the presence of several candidate genes that may be involved in epigenetic control, including two DNA methyltransferases (Dnmts). Dnmt1 and Dnmt2 are phase-specifically expressed in certain tissues. In the metathoracic ganglion, important in the serotonin pathway for sensing mechanostimulation, their expression is clearly affected by crowding. Our data urge for reconsidering the role of the endocrine system as being sandwiched in between genetics and epigenetics, involving complementary modes of action.
authors.affiliation: Research Group of Animal Physiology and Neurobiology, Biology Department, Leuven, Belgium. Bart.Boerjan@bio.kuleuven.be
authors.forename: Bart
authors.initials: B
authors.lastname: Boerjan
authors.forename: Filip
authors.initials: F
authors.lastname: Sas
authors.forename: Ulrich R
authors.initials: UR
authors.lastname: Ernst
authors.forename: Julie
authors.initials: J
authors.lastname: Tobback
authors.forename: Filip
authors.initials: F
authors.lastname: Lemière
authors.forename: Michiel B
authors.initials: MB
authors.lastname: Vandegehuchte
authors.forename: Colin R
authors.initials: CR
authors.lastname: Janssen
authors.forename: Liesbeth
authors.initials: L
authors.lastname: Badisco
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Marchal
authors.forename: Heleen
authors.initials: H
authors.lastname: Verlinden
authors.forename: Liliane
authors.initials: L
authors.lastname: Schoofs
authors.forename: Arnold
authors.initials: A
authors.lastname: De Loof
mesh_terms: D000818:Animals; D004703:Endocrine System / Q000378:metabolism*; D044127:Epigenesis, Genetic / Q000235:genetics / Q000502:physiology*; D005260:Female; D005298:Fertility / Q000235:genetics / Q000502:physiology; D006110:Grasshoppers / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D008136:Longevity / Q000235:genetics / Q000502:physiology