FLUORESCENT LABELING OF THE CYTOSKELETON IN CERAMIUM-STRICTUM (RHODOPHYTA)

Using rhodamine-phalloidin to detect F-actin/microfilaments and indire ct immunofluorescence to detect tubulin/microtubules, we studied the c ytoskeleton in axial cells of Ceramium strictum Harv., especially micr ofilaments and microtubules associated with cytoplasmic strands (trabe culae) that extend longitudinally through the central vacuole. As axia l cells attained mature size, trabeculae became progressively thinner, branched, and then broke down. An extensive microfilament array was p resent in peripheral parts of axial cells as well as in trabeculae. Mi crofilament array were highly disrupted by cytochalasin-B; this result ed in small irregular actin structures in axial cell peripheries and o ccasional dense aggregations at the base of cells. No actin-fluorescen ce was detected in intact trabeculae after cytochalasin-B treatment. M icrotubules formed a primary structural component in trabeculae, which were disrupted by griseofulvin (5 to 0.005 mu M) but reformed after t wo days in griseofulvin-free medium.