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| Author(s): |
Douglas Elias Santos
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Ribeirão Preto. |
| Institution: | Universidade de São Paulo (USP). Faculdade de Medicina de Ribeirão Preto (PCARP/BC) |
| Defense date: | 2017-05-19 |
| Examining board members: |
Klaus Hartmann Hartfelder;
Fábio Camargo Abdalla;
Luiz Carlos Carvalho Navegantes;
Ricardo Guelerman Pinheiro Ramos
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| Advisor: | Klaus Hartmann Hartfelder |
| Abstract | |
The connection between nutrition and phenotype is a particularly challenging issue in cases of facultative polyphenism, as for instance in the honeybee Apis mellifera. After studies on nutrient sensing pathways found unexpected modifications in these signaling pathways, a response to hypoxia was revealed as a possible mechanism underlying regulation of body size and organ growth. Since this response is closely linked to the metabolic conditions of the cells, the present study was designed to investigate the role of the mitochondrial and oxidative metabolism in the fat body of honeybee larvae, which is the metabolic center in insects, in the context of the caste differentiation process in A. mellifera. Based on the fact that honey bee larvae are reared in open brood cells, the queen and worker larvae should be exposed to equal oxygen diffusion conditions, and hence we investigated mitochondrial number and intracellular distribution, as well as rates of mitochondrial oxygen consumption in fat body cells during the larval stages critical for caste differentiation. By means of immunofluorescence and electron microscopy we found a higher density of mitochondria in the fat body of queen larvae. This result was corroborated by the quantification of mitochondrial functional units using a citrate synthase assay. Measurements of oxygen consumption obtained by high resolution respirometry revealed that queen larvae have higher maximum capacities of ATP production, with less physiological demand and higher mitochondrial efficiency than workers. Analysis of the expression of genes related to mitogenesis showed that Apis homologs of the transcription factors TFB1 and TFB2 and of the nutritional regulator, ERR are higher expressed in queen larvae. Despite differences in mitochondrial respiration, the two castes presented similar levels of lactate and hydrogen peroxide production, and without major chang in oxidative stress and cellular redox status. The high transcriptional levels of genes encoding enzymes of the antioxidant system, MnSOD and catalase observed in fat body cells of queen larvae guarantee that oxidative damage is reduced during larval development. These results are strong evidence that the differential nutrition of honey bee larvae by the adult worker, as the external stimulus for caste induction, differentially affects mitochondrial dynamics and functionality as an intrinsic element of phenotypic plasticity in this social insect. (AU) | |
| FAPESP's process: | 13/24733-7 - Oxidative metabolism in caste differentiation in honeybees: number and structure of gene expression and mitochondrial functional indicators |
| Grantee: | Douglas Elias Santos |
| Support Opportunities: | Scholarships in Brazil - Doctorate |