Genes involved in thoracic exoskeleton formation during the pupal-to-adult molt in a social insect model, Apis mellifera

Author(s)

Miranda Soares, Michelle Prioli ^[1] ; Barchuk, Angel Roberto ^[2] ; Quirino Simoes, Ana Carolina ^[3] ; Cristino, Alexandre dos Santos ^[4] ; de Paula Freitas, Flavia Cristina ^[1] ; Canhos, Luisa Lange ^[5] ; Gentile Bitondi, Marcia Maria ^[5]

Affiliation

^[1] Univ Sao Paulo, Fac Med Ribeirao Preto, Dept Genet, BR-14049 Ribeirao Preto, SP - Brazil

^[2] Univ Fed Alfenas, Inst Ciencias Biomed, Dept Biol Celular Tecidual & Desenvolvimento, Alfenas, MG - Brazil

^[3] Univ Fed ABC, Ctr Engn Modelagem & Ciencias Sociais Aplicadas C, Santo Andre, SP - Brazil

^[4] Univ Queensland, Queensland Brain Inst, Brisbane, Qld - Australia

^[5] Univ Sao Paulo, Fac Filosofia Ciencias & Letras Ribeirao Preto, Dept Biol, BR-14049 Ribeirao Preto, SP - Brazil

• Document type: Journal article
• Source: BMC Genomics; v. 14, AUG 28 2013.
• Web of Science Citations: 16

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. (AU)

• FAPESP's process: 10/16380-9 - Molecular genetics and hormonal regulation of exoskeleton differentiation in an insect model, Apis mellifera
• Grantee: Marcia Maria Gentile Bitondi
• Support Opportunities: Regular Research Grants
• FAPESP's process: 11/03171-5 - Causal analysis of Apis mellifera development: regulatory genes and hierachical networks of gene expression in the specification of tissue and organs
• Grantee: Zilá Luz Paulino Simões
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 07/04314-9 - Microarray analysis of genes expressed in the context of Apis mellifera metamorphosis
• Grantee: Michelle Prioli Miranda Soares
• Support Opportunities: Scholarships in Brazil - Doctorate