Full text
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| Author(s): |
Stella Noguera Pereira
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Instituto de Medicina Tropical de São Paulo (IMT) |
| Defense date: | 2017-11-10 |
| Examining board members: |
Lincoln Suesdek Rocha;
Enéas de Carvalho;
Karin Kirchgatter
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| Advisor: | Lincoln Suesdek Rocha |
| Abstract | |
Wolbachia pipientis is an obligate intracellular alpha-protobacterium, endosymbiont of arthropods and nematodes, which is inherited through maternal route over generations. The presence of this bacterium in germinative tissues can cause reproductive phenotypic alterations in the hosts, such as parthenogenesis, genetic feminization of males, death of males, cytoplasmic incompatibility (CI) and fitness changes. Some molecular mechanisms of these alterations are based on the modulation of gene expression of the host, that is, the bacterium can suppress or stimulate genes in order to produce favorable environment for the maintenance of the endosymbiosis. Due to this potential manipulator, Wolbachia has been tested as a \"tool\" for population control of pathogen vector insects. The mosquito Culex quinquefasciatus, naturally infected by Wolbachia in the Neotropical region, is an important vector of several pathogens that affect humans and animals. The presence of the bacteria causes CI and changes the fitness in the mosquito, through temporal changes in ovogenesis, reproductive fertility and fertility. The presence of Wolbachia is known to alter the expression of the grauzone gene and there are strong indications that this differential expression induces the CI in Cx. quinquefasciatus. It is known that this gene occurs with two paralogs copies in Cx. quinquefasciatus, but studies have observed the relevance of only one paralog as important regulator of oogenesis and spermatogenesis cell cycles. However, the genetic basis of the phenotypes \"changed fitness\" and CI of Wolbachia-Cx quinquefasciatus Neotropical model remain unknown. We initially aimed at quantifying and knockdown of grauzone gene (both paralogs) to support the preexisting hypothesis that overexpression of this gene in Wolbachia-infected mosquitoes causes reproductive phenotypic changes. During the development of the project there were intercurrences that altered the course of work: the need to replace mosquito populations due to demographic lows and the high intraspecific variability of grauzone gene. In view of the intercurrences we formulated the neo-objective phylogenetic comparison between the variants of the grauzone gene. We also detected variability in one of the paralogs and concluded that the paralogs copies of the gene contain structurally distinct and perhaps functionally distinct proteins with respect to the reproductive alteration (CI) caused by the presence of Wolbachia. It was possible to observe that infected females show more intense grauzone amplifications when compared to uninfected females on the 4th day of emergence, corroborating data from the literature. Taken together, these findings indicate that the continuity of the study of the role of grauzone in CI is promising, but also demonstrates that this gene is more complex than previously thought, which will require more investigative effort. The expectation of future use of Wolbachia as a biological control of mosquito-vectors may benefit from studies as proposed here. (AU) | |
| FAPESP's process: | 13/26014-8 - Influence of Wolbachia on the fitness of Culex quinquefasciatus |
| Grantee: | Stella Noguera Pereira |
| Support Opportunities: | Scholarships in Brazil - Master |