MITOCHONDRIA-DIVIDING RING - ULTRASTRUCTUAL BASIS FOR THE MECHANISM OF MITOCHONDRIAL DIVISION IN CYANIDIOSCHYZON MEROLAE

We present strong electron microscopic evidence that the mitochondrial-dividing,a ring (MD-ring) forms as a closed ring about 50 nm wide and 10 nm thick, at the contact point where the microbody attaches to the mitochondrion. This ring forms in the cytoplasm around an equatorial plane perpendicular to the major axis of a mitochondrion. As the MD-ring increases in both width and thickness, the mitochondrion becomes dumbbell-shaped with a narrow interconnecting isthmus. Then, by successive contractions of the ring, the dumbbell-shaped mitochondrion separates to generate two daughter mitochondria. We also observed formation of an electron dense plastid-dividing ring (PD-ring) during plastid divisions. We noted too the behaviour of the MB in relation to the contraction of MD-rings and PD-rings.