Sensory mechanisms controlling the timing of larval developmental and behavioral transitions require the Drosophila DEG/ENaC subunit, Pickpocket1

Abstract

Growth of multicellular organisms proceeds through a series of precisely timed developmental events requiring coordination between gene expression, behavioral changes, and environmental conditions. In Drosophila melanogaster larvae, the essential midthird instar transition from foraging (feeding) to wandering (non-feeding) behavior occurs prior to pupariation and metamorphosis. The timing of this key transition is coordinated with larval growth and size, but physiological mechanisms regulating this process are poorly understood. Results presented here show that Drosophila larvae associate specific environmental conditions, such as temperature, with food in order to enact appropriate foraging strategies. The transition from foraging to wandering behavior is associated with a striking reversal in the behavioral responses to food-associated stimuli that begins early in the third instar, well before food exit. Genetic manipulations disrupting expression of the Degenerin/Epithelial Sodium Channel subunit, Pickpocket1(PPK1) or function of PPK1 peripheral sensory neurons caused defects in the timing of these behavioral transitions. Transient inactivation experiments demonstrated that sensory input from PPK1 neurons is required during a critical period early in the third instar to influence this developmental transition. Results demonstrate a key role for the PPK1 sensory neurons in regulation of important behavioral transitions associated with developmental progression of larvae from foraging to wandering stage.

Serotonin and Downstream Leucokinin Neurons Modulate Larval Turning Behavior inDrosophila

“…The preparation was then fixed and stained as described previously (Nose et al, 1997). We used rabbit anti-GFP (Invitrogen; 1:1000), mouse anti-GFP (Sigma; 1:100), rabbit anti-5-HT (Sigma; 1:200), rabbit anti-leucokinin (Al-Anzi et al, 2010), rabbit antileucokinin receptor (Radford et al, 2002), rat anti-elav (Developmental Studies Hybridoma Bank), and mouse anti-V5 (Invitrogen; 1:500) as primary antibodies. We used goat anti-rabbit IgG conjugated with Alexa 488 (Invitrogen; 1:300), goat anti-mouse IgG conjugated with Alexa 488 (Invitrogen; 1:300), goat anti-rabbit IgG conjugated with Cy3 (Invitrogen; 1:300), and goat anti-mouse IgG conjugated with Alexa 555 (Invitrogen; 1:300) as secondary antibodies.…”

“…To gain insight into downstream pathway(s) of the 5-HT signaling, we next studied the expression pattern of the leucokinin receptor, which was described previously (Radford et al, 2002;Al-Anzi et al, 2010). Here, we focused our analyses on the expression in the larval VNC.…”

Pickpocket1 Is an Ionotropic Molecular Sensory Transducer

“…and cellular ablation studies demonstrate that complete loss of neuronal activity results in similar effects on behavior as the ppk1 ESB mutation (16,19,30). Therefore it is possible that the intrinsic activity of class IV md neurons could be dramatically altered in ppk1 ESB null mutants.…”

Behavioral Responses to Hypoxia in Drosophila Larvae Are Mediated by Atypical Soluble Guanylyl Cyclases

“…Food-associated taxis behaviors induced by temperature (Ainsley et al 2008), odorants (Fishilevich et al 2005), and light (Busto et al 1999) require that the animal integrates sensory inputs from its current environment for comparison with previously established environmental set points associated with a food source.…”

“…By measuring the number of stops and turns that a larva makes when exposed to a change in environment, we conducted a quantitative assessment of exploratory behavior in response to a uniform O 2 shift (Ainsley et al 2008). In the absence of food and O 2 shift, wild-type larvae showed an area-restricted search (ARS) behavior with a high number of stops and turns.…”