Abstract
The honeybee queen's egg-laying capacity is a crucial factor driving the productivity and success of the colony. Indeed, the reproductive capacity of the queen fuelled by the nutritional activity of the workers is the starting point of colony growth. However, the influence of nutrition on the quantity and quality of eggs has received limited attention in scientific studies. This thesis aims to explore the intricate relationship between nutrition, gene expression, and physiological processes in honeybees, focusing on the balance between protein and carbohydrate consumption and its effects on queen fecundity, egg, and worker gene expression.
Through nutritional geometry and statistical analysis, our study demonstrated the essential role of adequate nutrition in the queen's performance and embryo development, with protein and carbohydrate balance playing a significant role in determining the number and weight of eggs produced by the queen.
RNA-seq analysis was employed to examine gene expression in honeybee eggs under different nutritional treatments due to its high sensitivity, ability to detect novel transcripts, and capacity for quantitative analysis, revealing that the proportion of protein and carbohydrate in the diet influences gene expression patterns and providing a comprehensive understanding of gene regulation in response to nutritional variations. Enrichment in pathways related to RNA processing, nucleocytoplasmic transport, embryonic development, and the Hippo signalling pathway was observed in genes expressed under a certain amount of protein in the diet. Under this threshold, i.e., low protein diets, autophagy, mitophagy and inflammation pathways were enriched in the embryo. Therefore, our findings indicate that protein-deprived food negatively impacts embryonic development during the early stages through egg provisioning. However, our results suggest that nutrition's influence on gene expression in eggs is relatively minor compared to queen genotypic variations.
These discoveries underscore the critical role of queen genotype in gene expression during egg-laying, emphasizing the significance of queen selection and breeding based on her egg-laying capacity. Moreover, we identified optimal nutritional requirements for honeybee queen egg-laying (number and weight of eggs), which could be implemented in supplemental feeding practices in beekeeping and research.
The standardized method developed in our laboratory conditions holds promise for future research on the impact of food quantity, quality, and diversity on honeybee queen egg-laying. Additionally, this approach could shed light on future interplay of environmental factors, such as poor nutrition, diseases, and pesticides, on queen egg-laying and subsequent colony development.
Furthermore, our research identified specific genes as nutritional markers in honeybees. The study investigated the expression of genes related to nutritional and hormonal pathways, providing insights into the influence of nutrition on worker bees, responsible for processing food into royal jelly for larvae and the queen.
Overall, our study contributes to a deeper understanding of the complex relationship between nutrition, gene expression, and reproductive success in honeybee colonies. These findings have implications for beekeeping practices, colony management, queen breeding and honeybee conservation efforts.