Direct Evidence of Mitochondrial Nuclear Division in the Ultra-micro Alga Cyanidioschyzon merolae.

The fates of mitochondria and mitochondrial nuclei were followed in the “primitive” unicellular red alga Cyanidioschyzon merolae by microscopy and molecular biological techniques. The young mitochondrion contains one mitochondrial nucleus. The number of DNA molecules doubles during the late G2 phase and then returns to the normal value following division. The physical map of the mitochondrial genome was constructed and the size was determined. The genome was a single circle of about 32 kbp. Therefore, the mitochondrial nucleus contains 35 copies of mitochondrial DNA during interphase, which increases to 70 copies in late G2, and then decreases to 35 copies after mitochondrial division.