title: The MEKRE93 (Methoprene tolerant-Krüppel homolog 1-E93) pathway in the regulation of insect metamorphosis, and the homology of the pupal stage.
abstract: Recent studies on transcription factor E93 revealed that it triggers adult morphogenesis in Blattella germanica, Tribolium castaneum and Drosophila melanogaster. Moreover, we show here that Krüppel homolog 1 (Kr-h1), a transducer of the antimetamorphic action of juvenile hormone (JH), represses E93 expression. Kr-h1 is upstream of E93, and upstream of Kr-h1 is Methoprene-tolerant (Met), the latter being the JH receptor in hemimetabolan and holometabolan species. As such, the Met - Kr-h1 - E93 pathway (hereinafter named "MEKRE93 pathway") appears to be central to the status quo action of JH, which switch adult morphogenesis off and on in species ranging from cockroaches to flies. The decrease in Kr-h1 mRNA and the rise of E93 expression that triggers adult morphogenesis occur at the beginning of the last instar nymph or in the prepupae of hemimetabolan and holometabolan species, respectively. This suggests that the hemimetabolan last nymph (considering the entire stage, from the apolysis to the last instar until the next apolysis that gives rise to the adult) is ontogenetically homologous to the holometabolan pupa (also considered between two apolyses, thus comprising the prepupal stage).
authors.affiliation: Institut de Biologia Evolutiva (Universitat Pompeu Fabra-CSIC), Passeig Maritim de la Barceloneta 37, 0803 Barcelona, Spain. Electronic address: xavier.belles@ibe.upf-csic.es.
authors.forename: Xavier
authors.initials: X
authors.lastname: Belles
authors.affiliation: Institut de Biologia Evolutiva (Universitat Pompeu Fabra-CSIC), Passeig Maritim de la Barceloneta 37, 0803 Barcelona, Spain; Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brazil.
authors.forename: Carolina G
authors.initials: CG
authors.lastname: Santos
mesh_terms: D000818:Animals; D018507:Gene Expression Regulation, Developmental; D019476:Insect Proteins / Q000235:genetics / Q000378:metabolism; D007313:Insecta / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D007605:Juvenile Hormones / Q000502:physiology*; D051741:Kruppel-Like Transcription Factors / Q000378:metabolism; D008675:Metamorphosis, Biological / Q000502:physiology*; D009758:Nymph / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D011679:Pupa / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism
chemical_list: D019476:Insect Proteins; D007605:Juvenile Hormones; D051741:Kruppel-Like Transcription Factors; D012333:RNA, Messenger; D014157:Transcription Factors
keywords: Broad complex; E93; Ecdysone; Insect metamorphosis; Juvenile hormone; Krüppel homolog 1; Methoprene tolerant