Evaluation of Rice Varieties in Drosophila melanogaster

Abstract

There are many traditional rice varieties in the market that claim nutritional and health benefits. This work sought to understand the functional benefits of claims associated with Karungkuruvai, a black rice variety used in the Siddha system of medicine. First, we attempted to document the claims by holding discussions with stakeholders and reviewing available references in classical texts. Surprisingly, neither approach yielded a specific set of testable claims. Hence, available nutritional information on Karungkuruvai was deployed to assess how consuming this rice can impact physiology. Drosophila melanogaster, vinegar, or fruit fly was utilized as the animal model for experimentation. In flies, there is a strong co-relation between nutrition and life history traits. The quantity and quality of food provided impacts traits such as lifespan, resistance to stress, and fecundity. This study primarily employed fecundity (egg laying) as a readout for understanding the benefits of consuming Karungkuruvai (KK). Typical fly media is composed of corn flour, yeast and sugars. In our experiments, we compared how substitution of corn flour with Karungkuruvai or Ponni (a commonly consumed white rice variety) impacted fly fecundity. The experiments were conducted under two food regimens. Acute feeding where the rice diets were fed only for a short time as adults and continuous feeding where the flies were fed on these diets from egg to adult stages. In both regimens, KK fed flies displayed no difference in fecundity as compared to controls (corn flour). However, in acute feeding, flies fed on a Ponni diet exhibited 29% reduction in fecundity while on continuous feeding, they exhibited 48% reduction, as compared to controls. These differences were not due to feeding defects or differences in macronutrient compositions of the various flours. Surprisingly, 20d old flies exhibited a climbing deficit of ~ 56% on both rice diets. Further, we tested the effect of feeding the rice flours on early life malnourished flies. Remarkably, we observed that fecundity improved on a Ponni diet by 45% as compared to controls. Together, these suggest that Drosophila melanogaster can be used to study the functional benefits of rice varieties.