Labeling and Tracking Mitochondria with Photoactivation in Drosophila Embryos.

Mitochondria are relatively small, fragmented, and abundant in the large embryos of Drosophila, Xenopus and zebrafish. It is essential to study their distribution and dynamics in these embryos to understand the mechanistic role of mitochondrial function in early morphogenesis events. Photoactivation of mitochondrially tagged GFP (mito-PA-GFP) is an attractive method to highlight a specific population of mitochondria in living embryos and track their distribution during development. Drosophila embryos contain large numbers of maternally inherited mitochondria, which distribute differently at specific stages of early embryogenesis. They are enriched basally in the syncytial division cycles and move apically during cellularization. Here, we outline a method for highlighting a population of mitochondria in discrete locations using mito-PA-GFP in the Drosophila blastoderm embryo, to follow their distribution across syncytial division cycles and cellularization. Photoactivation uses fluorophores, such as PA-GFP, that can change their fluorescence state upon exposure to ultraviolet light. This enables marking a precise population of fluorescently tagged molecules of organelles at selected regions, to visualize and systematically follow their dynamics and movements. Photoactivation followed by live imaging provides an effective way to pulse label a population of mitochondria and follow them through the dynamic morphogenetic events during Drosophila embryogenesis.