Understanding taste and its modulation in Drosophila melanogaster

Dissecting Taste Neural circuits:
Taste is extremely important for all the organisms to evaluate and choose foods that are rich in calories and avoid bitter compounds that may be toxic. Like Humans, the tiny fruit fly -Drosophila melanogaster is able to taste amazingly similar range of organic molecules. Using their peripheral taste organs, flies detect different taste compounds in their environment. The axons of all the peripheral taste neurons terminate in the non-over lapping areas of the Subesophageal ganglion (SOG). SOG is the first relay for taste information in the fly brain. In contrast to the extensive knowledge on the peripheral coding of taste in flies and mammals, much less is known about the central pathways that relay and translate these signals into meaningful behavior.

By exploiting the gustatory system of flies, our lab is interested in understanding how do flies make the feeding decisions? Specifically, we are interested in understanding how the taste information is wired in the brain. To map the critical higher order features of the gustatory system such as processing and integration of the peripheral signals that give rise to appropriate behavioral responses, we are interested in dissecting the taste neural circuits that convey taste information to the brain and are involved in simple feeding behaviors like acceptance or rejection of food. Using various methods like molecular genetics techniques to mark taste neurons in the central nervous system, genetic means to suppress or activate the neuronal activity, feeding behavior assays, confocal microscopy, 3D modeling to generate taste map, electrophysiological and calcium imaging approaches to monitor taste induced activity in the brain would allow us to examine the taste processing in the fly brain. Identification of various neurons will provide valuable insight into the neural architecture of appetitive circuits such as those regulate feeding and reward.

Understanding Satiety:
The nervous system assesses the internal metabolic state and external chemosensory information to control hunger and satiety. While enjoying food, it is important that one should know when to stop when you are full. Metabolic conditions and eating disorders including obesity, diabetics, cardiovascular diseases and hypertension are affecting millions of people every year. Increased consumption of sweet products is a growing concern with medical authorities and it has been linked to the rising incidents of Diabetes and Obesity all over the world. Obesity alone is causing 3 million deaths every year. Hence, it is essential to balance the nutrient intake and maintain stable body weight to regulate metabolism. The lab is interested in exploring how the satiety is achieved by identifying neurons and genes involved. We will relate our findings to homologous mammalian genes with similar functions to discover conserved pathways that regulate hunger and satiety.

Modulation of taste behaviors:
Feeding behaviors are plastic. To understand state dependent alterations in the taste circuit activity, the extended interest of the lab is to understand how the activity of the taste circuits is modulated by intrinsic and extrinsic cues.

Disease carrying and crop destroying insects use their senses of taste and smell to find hosts and food. Insect borne diseases such as malaria, dengue fever and Chikungunya are transmitted via feeding behaviors. The results from simple models systems like Drosophila could potentially be applied to safe and cost effective pest control by improving insect trapping strategies and thus reduce pathogen transmission by insects and greatly benefit the agricultural industry and therefore society as a whole.

• Wellcome Trust-DBT Intermediate Fellow

• Sachin Kumar
  Research Scientist
  sachin@rcb.res.in
• Shrishti Sanghi
  Project associate
  srishti@rcb.res.in
• Pragya Kaul
  Research trainee
• Shivam Kaushik
  Research trainee
• Rahul Kumar
  Research trainee

1. Guda T, Kain P, Sharma K R, Pham C K, Ray A (2015) Repellent compound with larger protective zone than DEET identified through activity-screening of Ir40a neurons, does not require Or function. bioRxiv : 017145
2. Kain P,  Dahanukar A (2015) Secondary taste neurons that convey sweet taste and starvation in the Drosophila brain. Neuron 85:819
3. Badsha F, Kain P, Prabhakar S, Sundaram S, Padinjat R, Rodrigues V, Hasan G (2012) Mutants in Drosophila TRPC channels reduce olfactory sensitivity to carbon dioxide. PLoS One 7:e49848
4. Schmidt I, Thomas S, Kain P, Risse B, Naffin E, Klämbt C (2012) Kinesin heavy chain function in Drosophila glial cells controls neuronal activity. J Neurosci 32:7466
5. Kain P, Badsha F, Hussain SM, Nair A, Hasan G, Rodrigues V (2010) Mutants in phospholipid signaling attenuate the behavioral response of adult Drosophila to trehalose. Chem Senses 35:663
6. Kain P, Chandrashekaran S, Rodrigues V, Hasan G (2009) Drosophila mutants in phospholipid signaling have reduced olfactory responses as adults and larvae. J Neurogenet 23:303
7. Kain P, Chakraborty T S, Rodrigues V, Hasan G (2008) Multiplicity of G Protein Signalling Mechanisms in Drosophila Olfactory Transduction. Chemical Senses  33:S29
8. Kain P, Chakraborty TS, Sundaram S, Siddiqi O, Rodrigues V, Hasan G (2008) Reduced odor responses from antennal neurons of G(q)alpha, phospholipase Cbeta, and rdgA mutants in Drosophila support a role for a phospholipid intermediate in insect olfactory transduction. 28:4745

Patents

1. Ray A, Kain P, Pham C (2015) Methods for identifying arthropod repellents based on modulation of specific ionotropic receptors, and compounds and compositions identified by such methods. US Patent 14:853