title: RNAi-Mediated Functional Analysis of Bursicon Genes Related to Adult Cuticle Formation and Tanning in the Honeybee, Apis mellifera.
abstract: Bursicon is a heterodimeric neurohormone that acts through a G protein-coupled receptor named rickets (rk), thus inducing an increase in cAMP and the activation of tyrosine hydroxylase, the rate-limiting enzyme in the cuticular tanning pathway. In insects, the role of bursicon in the post-ecdysial tanning of the adult cuticle and wing expansion is well characterized. Here we investigated the roles of the genes encoding the bursicon subunits during the adult cuticle development in the honeybee, Apis mellifera. RNAi-mediated knockdown of AmBurs α and AmBurs β bursicon genes prevented the complete formation and tanning (melanization/sclerotization) of the adult cuticle. A thinner, much less tanned cuticle was produced, and ecdysis toward adult stage was impaired. Consistent with these results, the knockdown of bursicon transcripts also interfered in the expression of genes encoding its receptor, AmRk, structural cuticular proteins, and enzymes in the melanization/sclerotization pathway, thus evidencing roles for bursicon in adult cuticle formation and tanning. Moreover, the expression of AmBurs α, AmBurs β and AmRk is contingent on the declining ecdysteroid titer that triggers the onset of adult cuticle synthesis and deposition. The search for transcripts of AmBurs α, AmBurs β and candidate targets in RNA-seq libraries prepared with brains and integuments strengthened our data on transcript quantification through RT-qPCR. Together, our results support our premise that bursicon has roles in adult cuticle formation and tanning, and are in agreement with other recent studies pointing for roles during the pharate-adult stage, in addition to the classical post-ecdysial ones.
authors.affiliation: Departamento de Genética; Faculdade de Medicina de Ribeirão Preto; Universidade de São Paulo; Ribeirão Preto, SP, Brazil.|Departamento de Biologia; Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto; Universidade de São Paulo; Ribeirão Preto, SP, Brazil.
authors.forename: Claudinéia Pereira
authors.identifier: http://orcid.org/0000-0002-5458-4502
authors.initials: CP
authors.lastname: Costa
authors.affiliation: Departamento de Biologia; Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto; Universidade de São Paulo; Ribeirão Preto, SP, Brazil.
authors.forename: Moysés
authors.initials: M
authors.lastname: Elias-Neto
authors.affiliation: Departamento de Genética; Faculdade de Medicina de Ribeirão Preto; Universidade de São Paulo; Ribeirão Preto, SP, Brazil.
authors.forename: Tiago
authors.initials: T
authors.lastname: Falcon
authors.affiliation: Centro de Ciências Biológicas e da Saúde; Universidade Federal de Mato Grosso do Sul; Campo Grande, MS, Brazil.
authors.forename: Rodrigo Pires
authors.initials: RP
authors.lastname: Dallacqua
authors.affiliation: Departamento de Genética; Faculdade de Medicina de Ribeirão Preto; Universidade de São Paulo; Ribeirão Preto, SP, Brazil.
authors.forename: Juliana Ramos
authors.initials: JR
authors.lastname: Martins
authors.affiliation: Departamento de Biologia; Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto; Universidade de São Paulo; Ribeirão Preto, SP, Brazil.
authors.forename: Marcia Maria Gentile
authors.initials: MM
authors.lastname: Bitondi
mesh_terms: D000818:Animals; D001516:Bees / Q000235:genetics* / Q000254:growth & development; D000242:Cyclic AMP / Q000235:genetics; D026461:Ecdysteroids / Q000096:biosynthesis / Q000235:genetics*; D018507:Gene Expression Regulation, Developmental; D055785:Gene Knockdown Techniques; D007447:Invertebrate Hormones / Q000037:antagonists & inhibitors / Q000235:genetics*; D008675:Metamorphosis, Biological / Q000235:genetics*; D018978:Molting / Q000235:genetics; D034622:RNA Interference; D043562:Receptors, G-Protein-Coupled / Q000235:genetics; D014921:Wings, Animal / Q000254:growth & development / Q000378:metabolism
chemical_list: D026461:Ecdysteroids; D007447:Invertebrate Hormones; D043562:Receptors, G-Protein-Coupled; C002295:bursicon; D000242:Cyclic AMP