Fluorescent labelling of the cytoskeleton in Ceramium strictum (Rhodophyta)

Using rhodamine-phalloidin to detect F-actin/microfilaments and indirect immunofluorescence to detect tubulin/microtubules, we studied the cytoskeleton in axial cells of Ceramium strictum Harv., especially microfilaments and microtubules associated with cytoplasmic strands (trabeculae) that extend longitudinally through the central vacuole. As axial cells attained mature size, trabeculae became progressively thinner, branched, and then broke down. An extensive microfilament array was present in peripheral parts of axial cells as well as in trabeculae. Microfilament array were highly disrupted by cytochalasin-B; this resulted in small irregular actin structures in axial cell peripheries and occasional dense aggregations at the base of cells. No actin-fluorescence was detected in intact trabeculae after cytochalasin-B treatment. Microtubules formed a primary structural component in trabeculae, which were disrupted by griseofulvin (5 to 0.005 mu M) but reformed after two days in griseofulvin-free medium.