title: Exoskeleton formation in Apis mellifera: cuticular hydrocarbons profiles and expression of desaturase and elongase genes during pupal and adult development.
abstract: Cuticular hydrocarbons (CHCs) are abundant in the superficial cuticular layer (envelope) of insects where they play roles as structural, anti-desiccation and semiochemical compounds. Many studies have investigated the CHC composition in the adult insects. However, studies on the profiles of these compounds during cuticle formation and differentiation are scarce and restrict to specific stages of a few insect species. We characterized the CHCs developmental profiles in the honeybee workers during an entire molting cycle (from pupal-to-adult ecdyses) and in mature adults (forager bees). Gas chromatography/mass spectrometry (GC/MS) analysis revealed remarkable differences in the relative quantities of CHCs, thus discriminating pupae, developing and newly-ecdysed adults, and foragers from each other. In parallel, the honeybee genome database was searched for predicted gene models using known amino acid sequences of insect enzymes catalyzing lipid desaturation (desaturases) or elongation (elongases) as queries in BLASTP analysis. The expression levels of six desaturase genes and ten elongase genes potentially involved in CHC biosynthesis were determined by reverse transcription and real time polymerase chain reaction (RT-qPCR) in the developing integument (cuticle and subjacent epidermis). Aiming to predict roles for these genes in CHC biosynthesis, the developmental profiles of CHCs and desaturase/elongase transcript levels were evaluated using Spearman correlation coefficient. This analysis pointed to differential roles for these gene products in the biosynthesis of certain CHC classes. Based on the assumption that homologous proteins may share a similar function, phylogenetic trees were reconstructed as an additional strategy to predict functions and evolutionary relationships of the honeybee desaturases and elongases. Together, these approaches highlighted the molecular complexity underlying the formation of the lesser known layer of the cuticular exoskeleton, the envelope.
authors.affiliation: Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Av. Bandeirantes 3900, 14049-900 Ribeirão Preto, SP, Brazil.
authors.forename: Tiago
authors.initials: T
authors.lastname: Falcón
authors.affiliation: Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Av. Bandeirantes 3900, 14040-901 Ribeirão Preto, SP, Brazil.
authors.forename: Maria Juliana
authors.initials: MJ
authors.lastname: Ferreira-Caliman
authors.affiliation: Centro de Ciências Biológicas e da Saúde, Universidade Federal de São Carlos, Rod. Washington Luís, km 235, 13565-905 São Carlos, SP, Brazil.
authors.forename: Francis Morais
authors.initials: FM
authors.lastname: Franco Nunes
authors.affiliation: Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Av. Bandeirantes 3900, 14049-900 Ribeirão Preto, SP, Brazil.
authors.forename: Erica Donato
authors.initials: ED
authors.lastname: Tanaka
authors.affiliation: Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Av. Bandeirantes 3900, 14040-901 Ribeirão Preto, SP, Brazil.
authors.forename: Fábio Santos
authors.initials: FS
authors.lastname: do Nascimento
authors.affiliation: Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Av. Bandeirantes 3900, 14040-901 Ribeirão Preto, SP, Brazil. Electronic address: mmgbit@usp.br.
authors.forename: Márcia Maria
authors.initials: MM
authors.lastname: Gentile Bitondi
mesh_terms: D000123:Acetyltransferases / Q000235:genetics*; D000818:Animals; D001516:Bees / Q000235:genetics* / Q000254:growth & development; D004817:Epidermis / Q000737:chemistry*; D044943:Fatty Acid Desaturases / Q000235:genetics* / Q000378:metabolism; D000081031:Fatty Acid Elongases; D015870:Gene Expression; D017344:Genes, Insect; D006838:Hydrocarbons / Q000378:metabolism*; D008675:Metamorphosis, Biological / Q000235:genetics* / Q000502:physiology*; D010802:Phylogeny
chemical_list: D006838:Hydrocarbons; D044943:Fatty Acid Desaturases; D000123:Acetyltransferases; D000081031:Fatty Acid Elongases
keywords: Apis mellifera; Cuticular envelope; Cuticular hydrocarbons; Desaturase; Elongase; Insect exoskeleton