title: Genes involved in thoracic exoskeleton formation during the pupal-to-adult molt in a social insect model, Apis mellifera.
abstract: BACKGROUND
  The insect exoskeleton provides shape, waterproofing, and locomotion via attached somatic muscles. The exoskeleton is renewed during molting, a process regulated by ecdysteroid hormones. The holometabolous pupa transforms into an adult during the imaginal molt, when the epidermis synthe3sizes the definitive exoskeleton that then differentiates progressively. An important issue in insect development concerns how the exoskeletal regions are constructed to provide their morphological, physiological and mechanical functions. We used whole-genome oligonucleotide microarrays to screen for genes involved in exoskeletal formation in the honeybee thoracic dorsum. Our analysis included three sampling times during the pupal-to-adult molt, i.e., before, during and after the ecdysteroid-induced apolysis that triggers synthesis of the adult exoskeleton.
  
  
  RESULTS
  Gene ontology annotation based on orthologous relationships with Drosophila melanogaster genes placed the honeybee differentially expressed genes (DEGs) into distinct categories of Biological Process and Molecular Function, depending on developmental time, revealing the functional elements required for adult exoskeleton formation. Of the 1,253 unique DEGs, 547 were upregulated in the thoracic dorsum after apolysis, suggesting induction by the ecdysteroid pulse. The upregulated gene set included 20 of the 47 cuticular protein (CP) genes that were previously identified in the honeybee genome, and three novel putative CP genes that do not belong to a known CP family. In situ hybridization showed that two of the novel genes were abundantly expressed in the epidermis during adult exoskeleton formation, strongly implicating them as genuine CP genes. Conserved sequence motifs identified the CP genes as members of the CPR, Tweedle, Apidermin, CPF, CPLCP1 and Analogous-to-Peritrophins families. Furthermore, 28 of the 36 muscle-related DEGs were upregulated during the de novo formation of striated fibers attached to the exoskeleton. A search for cis-regulatory motifs in the 5'-untranslated region of the DEGs revealed potential binding sites for known transcription factors. Construction of a regulatory network showed that various upregulated CP- and muscle-related genes (15 and 21 genes, respectively) share common elements, suggesting co-regulation during thoracic exoskeleton formation.
  
  
  CONCLUSIONS
  These findings help reveal molecular aspects of rigid thoracic exoskeleton formation during the ecdysteroid-coordinated pupal-to-adult molt in the honeybee.
authors: Departamento de Biologia, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brasil. mmgbit@usp.br.
authors: Michelle Prioli Miranda
authors: MP
authors: Soares
authors: Angel Roberto
authors: AR
authors: Barchuk
authors: Ana Carolina Quirino
authors: AC
authors: Simões
authors: Alexandre
authors: A
authors: Dos Santos Cristino
authors: Flávia Cristina
authors: FC
authors: de Paula Freitas
authors: Luísa Lange
authors: LL
authors: Canhos
authors: Márcia Maria Gentile
authors: MM
authors: Bitondi
mesh_terms: D000595:Amino Acid Sequence; D060105:Animal Shells / Q000254:growth & development; D000818:Animals; D001483:Base Sequence; D001516:Bees / Q000166:cytology / Q000235:genetics* / Q000254:growth & development; D004817:Epidermis / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D063990:Gene Ontology; D053263:Gene Regulatory Networks; D017344:Genes, Insect; D019476:Insect Proteins / Q000235:genetics / Q000378:metabolism; D058977:Molecular Sequence Annotation; D008969:Molecular Sequence Data; D009024:Morphogenesis / Q000235:genetics*; D024510:Muscle Development / Q000235:genetics; D020411:Oligonucleotide Array Sequence Analysis; D011679:Pupa / Q000235:genetics / Q000254:growth & development; D013909:Thorax / Q000254:growth & development*; D059467:Transcriptome; D015854:Up-Regulation
chemical_list: D019476:Insect Proteins
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