Panel A shows fluorescence microscopy images, electron microscopy images, and merged overlays of import-competent and import-defective mitochondria. The lower panels show high-magnification electron microscopy images of three numbered mitochondrial structures. Panel B shows fluorescence microscopy images, electron microscopy images, merged overlays, and high-magnification electron microscopy images highlighting transferred mitochondrial structures and intracellular organelles. Panel C shows time-lapse fluorescence microscopy images acquired at 6 hours, 15 hours, and 33 hours, along with enlarged views showing mitochondrial transfer events in recipient cells.
Transferred import-defective and import-competent mitochondria undergo distinct forms of trans-mitophagy. (A) Top panel: Fluorescence microscopy image of transferred import-defective mitochondria (red arrows) correlated with the electron microscopy image. Bottom panel: Electron microscopy images of the indicated transferred lysosomal import-defective mitochondria. (B) Top panel: Fluorescence microscopy image of MDB (red arrow) correlated with the electron microscopy image. Middle panel: Electron microscopy of MDB containing potential ex-mitochondria (red arrows), lysosomes (blue arrows), and surrounded by a partial membrane (yellow arrows). Bottom panel: Electron microscopy images of indicated ex—import-competent mitochondria in MDB. (C) Stills from a movie of transferred import-competent mitochondria (su9-mScarlet) in a cell containing import-defective mitochondria (su9-mTagBFP2-DHFR +100 nM MTX) at the indicated time points after sorting, demonstrating MDB formation.