A transcriptional reporter of intracellular Ca(2+) in Drosophila.

Abstract

Intracellular Ca2+ is a widely used neuronal activity indicator. Here we describe a transcriptional reporter of intracellular Ca2+ (TRIC) in Drosophila, which uses a binary expression system to report Ca2+-dependent interactions between calmodulin and its target peptide. We show that in vitro assays predict in vivo properties of TRIC, and that TRIC signals in sensory systems depend on neuronal activity. TRIC can quantitatively monitor neuronal responses that change slowly, such as those of neuropeptide F-expressing neurons to sexual deprivation and neuroendocrine pars intercerebralis (PI) cells to food and arousal. Furthermore, TRIC-induced expression of a neuronal silencer in nutrient activated cells enhanced stress resistance, providing proof-of-principle that TRIC can be used for circuit manipulation. Thus, TRIC facilitates the monitoring and manipulation of neuronal activity, especially those reflecting slow changes in physiological states that are poorly captured by existing methods. TRIC’s modular design should enable optimization and adaptation to other organisms.