Reexamination of the pit plugs and the characteristic membranous structures in Porphyra yezoensis (Bangiales, Rhodophyta)

Abstract

C. Ueki, C. Nagasato, T. Motomura and N. Saga. 2008. Reexamination of the pit plugs and the characteristic membranous structures in Porphyra yezoensis (Bangiales, Rhodophyta). Phycologia 47: 5–11. DOI: 10.2216/07–12.1

Pit plug formation during conchosporogenesis in Porphyra yezoensis Ueda was studied with electron microscopy using freeze substitution. Just after nuclear division, cytokinesis started with furrowing of the septum. During furrowing, small vesicles were produced by projections of the plasma membrane in the space between the plasma membrane and the cell wall material and occasionally formed long chains. Afterwards, the plug core was gradually formed by endoplasmic reticulum, becoming vertical to the septum. The plasma membrane expanded like a loop along the pit plug from both sides of the furrowing septum. Lomasomes were located near the plasma membrane, beside the pit plug. With maturation of conchosporangia, the number of lomasomes increased near the pit plug. P. yezoensis has a characteristic expanding process of the plasma membrane along the pit plug, which is unique in the red algae.

Key Words::

• Cytokinesis
• Freeze-substitution
• Lomasome
• Pit plug formation
• Porphyra yezoensis
• Red algae

ACKNOWLEDGMENTS

We thank Prof. J. West, University of Melbourne, Australia, and Prof. J. Scott, College of William and Mary, USA, for critical reading of the manuscript and helpful suggestions. Chika Ueki was supported by a Research Fellowship of the Japan Society for the Promotion of Science for Young Scientists.