IDENTIFICATION OF A TRIPLE RING STRUCTURE INVOLVED IN PLASTID DIVISION IN THE PRIMITIVE RED ALGA CYANIDIOSCHYZON MEROLAE

Detailed structures of the plastid-dividing ring (PD ring) and the mit ochondrion-dividing ring (MD ring) of the primitive red alga Cyanidios chyzon merolae were examined by transmission electron microscopy (TEM) . Cells were highly synchronized to observe accurately their structure s. For the first time, TEM revealed a middle PD ring that lies between the inner and outer envelopes in addition to the outer ring on the cy toplasmic face of the outer envelope membrane and the inner ring on th e stromal face of the inner envelope membrane. The PD ring of C. merol ae is a triple ring structure, consisting of inner, middle and outer r ings.