Ionotropic Receptor-dependent cool cells control the transition of temperature preference in Drosophila larvae

Abstract

Temperature sensation guides animals to avoid temperature extremes and to seek their optimal temperatures. The larval stage of Drosophila development has a dramatic effect on temperature preference. While early-stage Drosophila larvae pursue a warm temperature, late-stage larvae seek a significantly lower temperature. Previous studies suggest that this transition depends on multiple rhodopsins at the late larval stage. Here, we show that early-stage larvae, in which dorsal organ cool cells (DOCCs) are functionally blocked, exhibit similar cool preference to that of wild type late-stage larvae. The molecular thermoreceptors in DOCCs are formed by three members of the Ionotropic Receptor (IR) family, IR21a, IR93a, and IR25a. Early-stage larvae of each Ir mutant pursue a cool temperature, similar to that of wild type late-stage larvae. At the late larval stage, DOCCs express decreased IR proteins and exhibit reduced cool responses. Importantly, late-stage larvae that overexpress IR21a, IR93a, and IR25a in DOCCs exhibit similar warm preference to that of wild type early-stage larvae. These data suggest that IR21a, IR93a, and IR25a in DOCCs navigate early-stage larvae to avoid cool temperatures and the reduction of these IR proteins in DOCCs results in animals remaining in cool regions during the late larval stage. Together with previous studies, we conclude that multiple temperature-sensing systems are regulated for the transition of temperature preference in fruit fly larvae.

Using TrackMate to Analyze Drosophila Larval and Adult Locomotion

“…Fig. 3A showed a setup for optogenetics previously used in the lab (Tyrrell et al, 2021). The light source was placed under an agar plate so the light source and light glares were recorded ( Fig.…”

“…The two-choice assay was performed as described with some modifications (Tyrrell et al, 2021). Two steel plates on different hot plates were separated by 1/16 inches (the release zone).…”

“…A sheet of a matte black poster was placed under the gel to reduce background noise signals and infrared light (4331910725, Amazon) was used to visualize the larvae. Two red-light sources (Tyrrell et al, 2021) were attached 10 inches above the gel at a 45° angle on both sides of the gel such that the light intensity was even throughout the gel (∼3 klux) and no glare was created. A third red-light source was placed in a box outside the experimental setup but within the view of the camera to serve as an indicator to record when red lights were on or off.…”

TACI: an ImageJ plugin for 3D calcium imaging analysis

“…This method uses TrackMate to track cells, identify ROI, and extract the fluorescence intensities of cells. Many studies, including a recent study from our lab [18], manually analyze calcium imaging. This manual process is time consuming and prone to human bias and error.…”

“…Calcium imaging data for S4_Figure in the previous study [18] were reanalyzed using the current method. Briefly, in fly larvae, dorsal organ cool neurons expressed the calcium indicator, GCaMP6 [17], by Ir21a-Gal4 [16].…”