TABLE 2.

Genetically encoded mitochondrial biosensors/tools developed in Drosophila.

Sensor line	Sensor type	Brief description	References
UAS-AT1.03NL/UAS-AT1.03RK	ATP sensor	FRET sensor for live imaging, consisting of an ATP binding sequence located between two fluorophores. Upon ATP binding the two are brought in close proximity leading to increased FRET signal.	Tsuyama et al., 2013
UAS-mitoGFP UAS-mitoDSRed	Mitochondrial marker	Green or Red fluorescent protein tagged with a mitochondrial import sequence (acting as targeting signal to the mitochondrial matrix), used to visualize all mitochondria in live or fixed tissue.	Lutas et al., 2012; DeVorkin et al., 2014; Chowdhary et al., 2017; Morris et al., 2020
UAS- mito-GCaMP3	Ca2 + sensor	Circularly permutated EGFP M13/Calmodulin fusion protein, tagged with a mitochondrial import sequence. Upon Ca2 + binding the construct undergoes a conformational change, increasing fluorophore output, thus allowing to monitor Ca2 + concentration in live cells.	Lutas et al., 2012; Morris et al., 2020
UAS-PercevalHR	ATP/ADP sensor	Fluorescent biosensor composed of three tandem copies of an ATP-binding protein fused to a circularly permuted monomeric Venus. It has a dual excitation spectrum, with a peak at 405 nm, enhanced by ATP binding and at 488 nm, enhanced by ADP binding. The ratiometric signal reports the occupancy and therefore ATP/ADP ration in live cells.	Morris et al., 2020; Wong et al., 2021
UAS-SoNaR	NADH/NAD + sensor	Fluorescent biosensor composed of a fusion of circularly permuted yellow fluorescent protein and an NADH-binding domain. It binds to NAD and NADH with two specific conformation, associated with a different excitation spectrum. The ratiometric signal reports the occupancy and therefore NADH/NAD + ratio in live cells.	Bonnay et al., 2020; Morris et al., 2020
UAS-mito-roGFP2-Grx1/UAS-mito-roGFP2-Orp1	REDOX sensors	Mitochondrially targeted, redox sensitive GFPs, with a dithiol/disulfide switch on their surface leading to measurable ratiometric fluorescent change in response to redox changes in live mitochondria. These are fused to glutaredoxin (Grx), which increases specificity for glutathione or a microbial Orp1 H2O2 sensor, making it specific for H2O2.	Albrecht et al., 2011; Morris et al., 2020
UAS-Dendra2.mito	Photoconvertible mitochondrial tag	Mitochondrially localized photoconvertible protein that can be irreversibly photoconverted from a green fluorescent form to a red fluorescent form, by UV-violet or blue light. It allows to monitor behavior of photoconverted mitochondria over time.	Hwang et al., 2014; Bertolin et al., 2018
UAS-mito-PyronicSF	Pyruvate sensor	Mitochondrially targeted pyruvate FRET sensor composed of a circularly permuted GFP fused to a bacterial pyruvate sensitive transcription factor. Upon pyruvate binding a conformational change leads to increased FRET signal.	Arce-Molina et al., 2020