The cell wall of the chlamydomonad flagellate,Gloeomonas kupfferi (Volvocales, Chlorophyta)

Summary

The large unicellular flagellate,Gloeomonas kupfferi, has recently been used as an important tool in chlamydomonad cell biology research, especially in studies dealing with the structure and function of the endomembrane system. However, little is known about the main secretory product, the cell wall. This study presents structural, chemical and immunological information about this wall. This 850–900 nm thick matrix is highly elaborate and consists of three distinct layers: an inner stratum (325 nm thick) consisting of tightly interwoven fibers, a medial crystalline layer consisting of 22–23 nm subunits and an outer wall layer (500 nm thick) of outwardlyradiating fibrils. Rapid freeze-deep etch analysis reveals that the 35–40 nm fibers of the outer layer form a quasi-lattice of 160 nm subunits. The outer wall can be removed from whole pellets using the chelator, CDTA. The medial wall complex can be solubilized by perchlorate. SDS-gel electrophoresis reveals that the perchlorate soluble-material consists of five high molecular weight glycoproteins and five major low molecular weight glycoproteins. The electrophoretic profile is roughly similar to that ofChlamydomonas reinhardtii. Antibodies were successfully raised against the outer wall component and were shown to label the outer wall layer.