A single pair of pharyngeal neurons functions as a commander to reject high salt in Drosophila melanogaster.

Salt (NaCl), is an essential nutrient for survival, while excessive salt can be detrimental. In the fruit fly, Drosophila melanogaster, internal taste organs in the pharynx are critical gatekeepers impacting the decision to accept or reject a food. Currently, our understanding of the mechanism through which pharyngeal gustatory receptor neurons (GRNs) sense high salt are rudimentary. Here, we found that a member of the ionotropic receptor family, Ir60b, is expressed exclusively in a pair of GRNs activated by high salt. Using a two-way choice assay (DrosoX) to measure ingestion volume, we demonstrate that IR60b and two co-receptors IR25a and IR76b are required to prevent high salt consumption. Mutants lacking external taste organs but retaining the internal taste organs in the pharynx exhibit much higher salt avoidance than flies with all taste organs but missing the three IRs. Our findings highlight the vital role for IRs in a pharyngeal GRN to control ingestion of high salt.

A single pair of pharyngeal neurons functions as a commander to reject high salt in Drosophila melanogaster.

Salt is an essential nutrient for survival, while excessive NaCl can be detrimental. In the fruit fly, Drosophila melanogaster, internal taste organs in the pharynx are critical gatekeepers impacting the decision to accept or reject a food. Currently, our understanding of the mechanism through which pharyngeal gustatory receptor neurons (GRNs) sense high salt are rudimentary. Here, we found that a member of the ionotropic receptor family, Ir60b, is expressed exclusively in a pair of GRNs activated by high salt. Using a two-way choice assay (DrosoX) to measure ingestion volume, we demonstrate that IR60b and two coreceptors IR25a and IR76b, are required to prevent high salt consumption. Mutants lacking external taste organs but retaining the internal taste organs in the pharynx exhibit much higher salt avoidance than flies with all taste organs but missing the three IRs. Our findings highlight the vital role for IRs in a pharyngeal GRN to control ingestion of high salt.

Cellular and molecular basis of IR3535 perception in Drosophila.

BACKGROUND: IR3535 is among the most widely used synthetic insect repellents, particularly for the mitigation of mosquito-borne diseases such as malaria, yellow fever, dengue and Zika, as well as to control flies, ticks, fleas, lice and mites. These insects are well-known vectors of deadly diseases that affect humans, livestock and crops. Moreover, global warming could increase the populations of these vectors. RESULTS: Here, we performed IR3535 dose-response analyses on Drosophila melanogaster, a well-known insect model organism, using electrophysiology and binary food choice assays. Our findings indicated that bitter-sensing gustatory receptor neurons (GRNs) are indispensable to detect IR3535. Further, potential candidate gustatory receptors were screened, among which GR47a was identified as a key molecular sensor. IR3535 concentrations in the range 0.1-0.4% affected larval development and mortality. In addition, N,N-diethyl-m-toluamide (DEET, another commonly used insecticide) was found to exert synergistic effects when co-administered with IR3535. CONCLUSION: Our findings confirmed that IR3535 directly activates bitter-sensing GRNs, which are mediated by GR47a. This relatively safe and highly potent insecticide can be largely used in combination with DEET to increase its efficiency to protect livestock and crops. Collectively, our findings suggest that the molecular sensors elucidated herein could be used as targets for the development of alternative insecticides. © 2021 Society of Chemical Industry.

Isolation and Characterization of Potential Antibiotic-Producing Actinomycetes from Water and Soil Sediments of Different Regions of Nepal.

INTRODUCTION: The actinomycetes are diversely distributed microorganisms in nature. The geographical diversity of Nepal is suitable for adaptation of various species of actinomycetes. The distribution of the actinomycetes is dependent upon the altitude and nature of the soil and water. METHODS: A total of 22 water and soil samples were collected from different regions of Nepal and were processed. Different isolates were characterized by observing colony characteristics and microscopic characteristics. Screening of the antimicrobial property was based upon perpendicular line streaking and submerged-state fermentation for antibiotic production. RESULTS: From the identification tool used, 12 were found to be Micromonospora, 9 were Nocardia, and 7 were Streptomyces. Out of total samples, 8 isolates of actinomycetes were tested effective against the tested bacteria by primary screening using the well diffusion method. Among the primarily screened, all isolates were subjected to submerged-state fermentation methods to produce crude extracts and 4 were found to be effective against the tested bacterial group. The actinomycetes identified from a water source showed better antimicrobial property towards the tested bacteria than the soil sample. Most isolates were found to be Micromonospora followed by Nocardia and Streptomyces with higher antimicrobial activities. CONCLUSION: The water source and soil sediments of Nepal provide suitable environments for actinomycetes towards obtaining a novel antimicrobial agent. The study of actinomycetes from various unexploited areas of Nepal is necessary. Thus, exploitation of various regions of Nepal for the discovery of an effective antimicrobial agent is helpful in providing a solution to the cost-effective therapy and action against antibiotic resistance.