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Karina R. Guidugli

Bio: Karina R. Guidugli is an academic researcher from University of São Paulo. The author has contributed to research in topics: Vitellogenin & Hemolymph. The author has an hindex of 7, co-authored 7 publications receiving 960 citations.

Papers
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TL;DR: To dissect gene function in the adult stage, the intra-abdominal injection technique seems superior to egg injection as it gives a much higher penetrance, it is much simpler, and it makes it possible to address genes that are also expressed in the embryonic, larval or pupal stages.
Abstract: The ability to manipulate the genetic networks underlying the physiological and behavioural repertoires of the adult honeybee worker (Apis mellifera) is likely to deepen our understanding of issues such as learning and memory generation, ageing, and the regulatory anatomy of social systems in proximate as well as evolutionary terms. Here we assess two methods for probing gene function by RNA interference (RNAi) in adult honeybees. The vitellogenin gene was chosen as target because its expression is unlikely to have a phenotypic effect until the adult stage in bees. This allowed us to introduce dsRNA in preblastoderm eggs without affecting gene function during development. Of workers reared from eggs injected with dsRNA derived from a 504 bp stretch of the vitellogenin coding sequence, 15% had strongly reduced levels of vitellogenin mRNA. When dsRNA was introduced by intra-abdominal injection in newly emerged bees, almost all individuals (96 %) showed the mutant phenotype. An RNA-fragment with an apparent size similar to the template dsRNA was still present in this group after 15 days. Injection of dsRNA in eggs at the preblastoderm stage seems to allow disruption of gene function in all developmental stages. To dissect gene function in the adult stage, the intra-abdominal injection technique seems superior to egg injection as it gives a much higher penetrance, it is much simpler, and it makes it possible to address genes that are also expressed in the embryonic, larval or pupal stages.

317 citations

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TL;DR: It is shown here that silencing of vitellogenin expression causes a significant increase in JH titer and its putative receptor, which corresponds to a dynamic dose–response.

295 citations

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TL;DR: Phylogenetic analysis of vitellogenin sequences available in insects gave a tree that is congruent with the currently accepted insect phylogenetic schemes.

163 citations

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TL;DR: Southern analysis indicates that the Vg gene is present as a single copy in the honeybee genome and in vivo hormone treatment experiments suggest that the decrease of 20-hydroxyecdysone concentration occurring in previtellogenic phases allows Vg production.
Abstract: In the honeybee, Apis mellifera, vitellogenin (Vg) expression has been detected in the ovary of queens, but not in that of workers. In addition, larvae of both sexes produce Vg in significant amounts, which suggest that Vg serves for functions additional to oocyte growth and energy supply to the embryo. In vivo hormone treatment experiments suggest that the decrease of 20-hydroxyecdysone concentration occurring in previtellogenic phases allows Vg production. Southern analysis indicates that the Vg gene is present as a single copy in the honeybee genome. Arch. Insect Biochem. Physiol. 59:211–218, 2005. © 2005 Wiley-Liss, Inc.

115 citations

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TL;DR: Experiments designed to verify the influence of the diet on Hex 70b expression showed similar transcript amounts in adult workers fed on a protein-enriched diet or fed exclusively on sugar, however, sugar-fed workers responded to the lack of dietary proteins by diminishing significantly the amount of HEX 70b subunits in hemolymph.

57 citations


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26 Oct 2006-Nature
TL;DR: The genome sequence of the honeybee Apis mellifera is reported, suggesting a novel African origin for the species A. melliferA and insights into whether Africanized bees spread throughout the New World via hybridization or displacement.
Abstract: Here we report the genome sequence of the honeybee Apis mellifera, a key model for social behaviour and essential to global ecology through pollination. Compared with other sequenced insect genomes, the A. mellifera genome has high A+T and CpG contents, lacks major transposon families, evolves more slowly, and is more similar to vertebrates for circadian rhythm, RNA interference and DNA methylation genes, among others. Furthermore, A. mellifera has fewer genes for innate immunity, detoxification enzymes, cuticle-forming proteins and gustatory receptors, more genes for odorant receptors, and novel genes for nectar and pollen utilization, consistent with its ecology and social organization. Compared to Drosophila, genes in early developmental pathways differ in Apis, whereas similarities exist for functions that differ markedly, such as sex determination, brain function and behaviour. Population genetics suggests a novel African origin for the species A. mellifera and insights into whether Africanized bees spread throughout the New World via hybridization or displacement.

1,673 citations

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TL;DR: In this paper, the authors used double-stranded RNA (dsRNA) as a diet component to suppress gene expression in nematodes and showed that feeding with dsRNA can be effective in downregulating targeted genes.

547 citations

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TL;DR: This is the first demonstration of RNAi following ingestion of dsRNA in all of the species tested, and the method offers promise of both higher throughput RNAi screens and the development of a new generation of species-specific insecticides.

542 citations

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TL;DR: The hypothesis that caste-specific differences in Vg expression are involved in queen longevity is supported and conserved and species-specific mechanisms interact to regulate queen bee longevity without sacrificing fecundity.
Abstract: In most animals, longevity is achieved at the expense of fertility, but queen honey bees do not show this tradeoff. Queens are both long-lived and fertile, whereas workers, derived from the same genome, are both relatively short-lived and normally sterile. It has been suggested, on the basis of results from workers, that vitellogenin (Vg), best known as a yolk protein synthesized in the abdominal fat body, acts as an antioxidant to promote longevity in queen bees. We explored this hypothesis, as well as related roles of insulin–IGF-1 signaling and juvenile hormone. Vg was expressed in thorax and head fat body cells in an age-dependent manner, with old queens showing much higher expression than workers. In contrast, Vg expression in worker head was much lower. Queens also were more resistant to oxidative stress than workers. These results support the hypothesis that caste-specific differences in Vg expression are involved in queen longevity. Consistent with predictions from Drosophila, old queens had lower head expression of insulin-like peptide and its putative receptors than did old workers. Juvenile hormone affected the expression of Vg and insulin–IGF-1 signaling genes in opposite directions. These results suggest that conserved and species-specific mechanisms interact to regulate queen bee longevity without sacrificing fecundity.

529 citations

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TL;DR: Although both Tribolium and C. elegans show a robust systemic RNAi response, the genome-wide survey reveals significant differences between the RNAi mechanisms of these organisms.
Abstract: Background: RNA interference (RNAi) is a highly conserved cellular mechanism. In some organisms, such as Caenorhabditis elegans, the RNAi response can be transmitted systemically. Some insects also exhibit a systemic RNAi response. However, Drosophila, the leading insect model organism, does not show a robust systemic RNAi response, necessitating another model system to study the molecular mechanism of systemic RNAi in insects. Results: We used Tribolium, which exhibits robust systemic RNAi, as an alternative model system. We have identified the core RNAi genes, as well as genes potentially involved in systemic RNAi, from the Tribolium genome. Both phylogenetic and functional analyses suggest that Tribolium has a somewhat larger inventory of core component genes than Drosophila, perhaps allowing a more sensitive response to double-stranded RNA (dsRNA). We also identified three Tribolium homologs of C. elegans sid-1, which encodes a possible dsRNA channel. However, detailed sequence analysis has revealed that these Tribolium homologs share more identity with another C. elegans gene, tag130. We analyzed tag-130 mutants, and found that this gene does not have a function in systemic RNAi in C. elegans. Likewise, the Tribolium sid-like genes do not seem to be required for systemic RNAi. These results suggest that insect sid-1-like genes have a different function than dsRNA uptake. Moreover, Tribolium lacks homologs of several genes important for RNAi in C. elegans. Conclusion: Although both Tribolium and C. elegans show a robust systemic RNAi response, our genome-wide survey reveals significant differences between the RNAi mechanisms of these organisms. Thus, insects may use an alternative mechanism for the systemic RNAi response. Understanding this process would assist with rendering other insects amenable to systemic RNAi, and may influence pest control approaches.

501 citations