The addition of either soybean protein isolate or lysine to the diet of Drosophila melanogaster affects viability and position-effect variegation

With the growing emphasis on dietary plant-based protein, revealing its potential nutritional and health benefits has become imperative. This study employed a Drosophila melanogaster -based model to investigate the effects of a protein-rich diet on viability and phenotypic variability, including survival rate, organ size, and eye colour, which could also identify potential epigenetic modifications. Diets that were either restricted to soybean protein or enriched with it were compared with lysine supplementation, a single essential amino acid. The results showed that dietary restriction reduced larval brain size and overall pupal size compared to the normal conditions. This also raised the potential for epigenetic modification, which manifests as an intensification of the white-eyed phenotype in the w m4h genotype. In low protein concentrations, lysine was essential for D. melanogaster development, but protein intake was insufficient for the larvae to complete their development into pupae. In contrast, higher lysine concentrations appeared to be associated with complete larval developmental failure, suggesting potential toxicity; however, the specific mechanism requires further investigation. Our results emphasise the importance of considering nutrient quality and quantity when designing specific dietary interventions.