Visualization of the cytoskeleton in red algae using fluorescent labelling

summary Cytoskeletal components have been visualized for the first time in red algae using fluorescent labelling. Rhodamine‐phalloidin was used to stain actin in a variety of filamentous species: Griffithsia pacifica, Tiffaniella snyderae, Ceramium strictum, Antithamnion kylinii (Ceramiales) and Audouinella dasyae (Acrochaetiales). Immunofluorescent labelling of microtubules was obtained only in Griffithsia pacifica. In both procedures, successful labelling was achieved only after wall digestion with glucuronidase and protocols using cellulase resulted in no labelling. Both microfilaments and microtubules formed extensive arrays in the peripheral cytoplasm of Griffithsia. Microtubules were associated with nuclei in these highly multinucleate cells, suggesting that they maintain the extremely regular nuclear arrangement. Dense labelling of microfilaments occurred at rhizoid apices, however, this was not observed in apical cells, suggesting that two distinct mechanisms of tip growth may be present. Of the algae studied, only Griffithsia formed extensive peripheral arrays of microfilaments in all cells; the remaining genera showed actin labelling in a variety of different structures including, long and short ‘ropes’ of varying thicknesses, basket‐like structures and ‘spikes’. In Griffithsia extensive actin staining was often associated with the pit plugs between adjoining cells. Cytoskeletal components often showed a polar distribution with denser labelling towards the bases or apices of cells. In dividing apical cells of Griffithsia , a band of microfilaments was observed prior to deposition of the new cross wall. These preliminary results suggest that cytoskeletal studies will provide important insights into understanding development and cell function in red algae.