Mitochondrial fragmentation in early germarium. (A) A representative electron micrograph of wild-type early germarium obtained by FIB-SEM. Sample milling was performed from the anterior tip of the germarium toward the posterior (arrow). The image is a single section of xz plane after 3D reconstruction. Region 1 and region 2A cysts are outlined with yellow and green dashed lines, respectively. Scale bar, 5 µm. (B) The detailed structures of mitochondria and other subcellular components in region 1 and region 2A of wild-type and Fis1 knockdown by bam-gal4. The arrows point to ring canals between the germ cells and fusomes, which were used to trace the germ cells within a cyst. Scale bar, 2 µm. (C and D) Frequency distribution of mitochondrial volume in region 1 (n = 808 mitochondria) and region 2A (n = 4,782 mitochondria) of wild-type germarium (C), and those in region 2A of wild-type and Fis1 knockdown (n = 4,893 mitochondria) germarium. (D) The proportion of mitochondria in the indicated range of volume. (E) The proportion of mitochondria with bigger (>0.05 µm3) volume from each experimental group (ctrl region 1, n = 808; ctrl region 2A, n = 4,782; Fis1-KD region 1, n = 510; Fis1-KD region 2A, n = 4,893).
