Characterization of the Decision Network for Wing Expansion inDrosophilaUsing Targeted Expression of the TRPM8 Channel

Abstract

After emergence, adult flies and other insects select a suitable perch and expand their wings. Wing expansion is governed by the hormone bursicon and can be delayed under adverse environmental conditions. How environmental factors delay bursicon release and alter perch selection and expansion behaviors has not been investigated in detail. Here we provide evidence that in Drosophila the motor programs underlying perch selection and wing expansion have different environmental dependencies. Using physical manipulations, we demonstrate that the decision to perch is based primarily on environmental valuations and is incrementally delayed under conditions of increasing perturbation and confinement. In contrast, the all-or-none motor patterns underlying wing expansion are relatively invariant in length regardless of environmental conditions. Using a novel technique for targeted activation of neurons, we show that the highly stereotyped wing expansion motor patterns can be initiated by stimulation of N CCAP , a small network of central neurons that regulates the release of bursicon. Activation of this network using the cold-sensitive rat TRPM8 channel is sufficient to trigger all essential behavioral and somatic processes required for wing expansion. The delay of wing expansion under adverse circumstances thus couples an environmentally sensitive decision network to a command-like network that initiates a fixed action pattern. Because N CCAP mediates environmentally insensitive ecdysis-related behaviors in Drosophila developmentbeforeadultemergence,thestudyofwingexpansionpromisesinsightsnotonlyintohownetworksmediatebehavioralchoices,but also into how decision networks develop.

Channelrhodopsin-2–XXL, a powerful optogenetic tool for low-light applications

“…However, this technique cannot be efficiently used for large numbers of animals (3,14). Thermogenetic effectors, such as dTRPA1 (11,12) or the mammalian cold-sensitive TRPM8 channel (13), have been very successfully used in Drosophila. Although of undisputed utility, these tools come at the cost of undesired off-target effects, are unsuited for studying temperature-dependent processes (such as, e.g., temperaturepreference behavior) (45), and are of limited use in warm-blooded animals.…”

“…Due to these restrictions in Drosophila, ChR2 has not reached the popularity attained in other organisms, and instead the field has turned mainly to thermogenetic neuronal stimulation (11)(12)(13). As with all techniques, there are also drawbacks to using temperature as a stimulus, such as undesired background activity and a multitude of temperature-sensitive cellular processes and behavioral responses.…”

Potency of Transgenic Effectors for Neurogenetic Manipulation inDrosophilaLarvae

“…TRPA1 channels activate in response to warm temperatures (Viswanath et al 2003). In contrast, rat TRPM8 is responsible for sensing mild cold temperatures (Colburn et al 2007;Peabody et al 2009). UAS-Channelrhodopsin2 (UAS-ChR2-wt and UASChR2-XXL), UAS-Paca, and UAS-bPac expression was successfully used for optogenetic cell manipulation (see Table S1).…”

Aging impairs intermediate-term behavioral memory by disrupting the dorsal paired medial neuron memory trace

“…5A). The TrpM8 channel is activated at lower than 18°C (20)(21)(22). We tested 1-h memory of flies expressing uas-trpM8 in DPM neurons, those expressing only the c316-Gal4 driver, and flies carrying only the uas-trpM8 transgene.…”

“…Heat treatment of only 60 s incapacitates flies expressing TrpA1 throughout the nervous system (23), whereas 5 min of cold treatment at 15°C is required to incapacitate flies expressing one copy of TrpM8 (22). Initially, we stimulated the DPM neurons by incubating flies expressing TrpA1 in the DPM neurons at 32°C between training and testing.…”