International Union for the Study of Social Insects (IUSSI2018), August 5-10, 2018 in Guarujá, Brazil.

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Effects of narcosis on senescence parameters and expression of candidate genes in Apis mellifera workers

Author(s):
Giovana Craveiro, Giovana Craveiro , Mário Sérgio Cervoni , Carlos Antônio Mendes Cardoso-Júnior , Karina Rosa Guidugli-Lazzarini , Klaus Hartfelder
Institution(s):
Departamento Genética, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brazil; Departamento Genética, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brazil ; Departamento de Biologia Celular e Molecular e Bioagentes Patogênicos, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brazil ; Departamento de Biologia Celular e Molecular e Bioagentes Patogênicos, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brazil ; Departamento Genética, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brazil ; Departamento de Biologia Celular e Molecular e Bioagentes Patogênicos, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brazil
Honey bee workers are responsible for maintaining the colony, including brood care, hive cleaning, guarding and foraging. The performance of these tasks is associated with a bee’s age in a mechanism known as age polyethism, or behavioral maturation. While young workers preferentially perform tasks within the hive, the older ones become foragers. The transition from such intra- to extranidal tasks is accompanied by a process termed immunosenescence. Previous studies have shown that the gas CO2 is capable of accelerating this transition and also to promote senescence in adult workers. To understand the morphophysiological and molecular mechanisms underlying this effect, workers of known age were exposed to CO2. With regard to hypopharyngeal gland morphology, an advance was observed in the regression of the acini in bees narcotized with CO2, similar to the morphological profile seen with glands of older, foraging bees. Senescence parameters in the fat body, the center of the intermediary metabolism of insects, was investigated using immunofluorescence detection of the ATP synthase subunit 5α and enzymatic quantification of citrate synthase activity. This revealed an increase in functional mitochondrial units in the CO2-treated bees. Mitochondrial biogenesis factor genes (tfam and tfb2), the three core genes of the hypoxia response pathway (fatiga, sima and tango), and the epigenetic modifier gene dnmt3, which encodes a de novo DNA methyltransferase, all showed a tendency towards an increase in transcript levels in response to the CO2 narcosis, whereas the transcript levels of the vitellogenin gene were markedly reduced. Taken together these results lead to infer that a CO2 narcosis induces morphological characteristics and cellular and gene expression responses compatible with the natural senescence process seen in A. mellifera workers that undergo the age-related nurse-to forager transition.Funding acknowledgment: FAPESP grant 2017/09128-0.
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