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Molecular Characterization of Chemosensory Genes and Transcriptome of Antenna of Screwworm fly, Cochliomyia hominivorax (Diptera: Calliphoridae)


The species Cochliomyia hominivorax (Diptera: Calliphoridae), popularly known as the screwworm, is an important obligate ectoparasite that causes traumatic myiasis in warm-blooded vertebrates, especially in domestic animals. The pregnant females of the species locate wounds exposed in the host where they deposit their eggs. After hatching, the larvae feed on the living tissues of the host, which represents an important obstacle to animal breeding. It causes economic losses to Brazilian cattle breeding around US$ 300 million per year. The location and choice of oviposition sites by C. hominivorax females is mediated by the chemosensory perception of chemical molecules emitted by the host during colonization of wounds by bacterial agents. In insects, chemical volatiles (odors) are identified by two multigenic receptor families: Olfactory Receptors (ORs) and Ionotropic Receptors (IRs). These receptors identify the odor molecules carried by Odorant Binding Proteins (OBPs) and are present in chemosensory structures called sensilla, which are distributed in peripheral structures of the insect, such as antennas. Although we know that the location of oviposition sites by C. hominivorax females is mediated by the identification of chemical compounds, it is not yet known which receptors are involved in such behavior. The screwworm is the only fly that causes obligatory myiasis in the Neotropical region. This type of behavior is not observed in most of the phylogenetically close species of the screwworm, such as Chrysomya megacephala which is saprophytic. The latter deposits its eggs in decomposing organic matter, where the larvae will develop. In this context, our hypothesis is that chemosensory genes, mainly olfactory, had played a critical role in the transition from the free-living habit (as observed in Ch. megacephala) to the obligate parasitism, present in C. hominivorax, being crucial in the detection of sites for oviposition. Therefore, the present project aims to investigate if the expression of the chemosensory genes may be related to the obligatory ectoparasite habit in screwworm fly. To this end, the project has the following main objectives: (i) to annotate, characterize and compare the main families of olfactory chemosensory genes (ORs and IRs) and Odorant Binding Proteins (OBPs) in the genome of C. hominivorax and Ch. megacephala; and (ii) to analyze the expression profile of these genes in the antenna (main olfactory organ in insects) of C. hominivorax and Ch. megacephala females in response to odor emitted from potential oviposition sites using large-scale mRNA sequencing (RNA-Seq). Other gene families that are differentially expressed will also be investigated, but efforts will be concentrated on ORs, IRs and OBPs. In combination, these investigations will be fundamental for a better understanding of the molecular mechanisms responsible for the behavioral responses mediated by olfactory genes in C. hominivorax, mainly related to the mechanisms responsible for locating sites for oviposition. The data generated by this project will contribute to studies of functional, comparative and evolutionary genomics in the Calliphoridae family, currently under development in LabGEA, generating information crucial for a better understanding of the evolution of obligatory ectoparasite habit in C. hominivorax. In addition, the results of this project have the potential to refine our current knowledge about how this species recognizes, locates and infests so efficiently a living host, assisting in the future the development of new control strategies in Brazil and other regions of South and Central Americas, where the economic damages to the health and animal production persist. (AU)

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(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)
GONCALVES, ROGERIO MARTINS; MASTRANGELO, THIAGO; VERLE RODRIGUES, JOSE CARLOS; PAULO, DANIEL FERNANDO; OMOTO, CELSO; CORREA, ALBERTO SOARES; LIMA DE AZEREDO-ESPIN, ANA MARIA. Invasion origin, rapid population expansion, and the lack of genetic structure of cotton bollworm (Helicoverpa armigera) in the Americas. ECOLOGY AND EVOLUTION, v. 9, n. 13, p. 7378-7401, . (14/11495-3, 14/10504-9, 18/04478-6, 15/02079-9)

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