VISUALIZATION OF THE CYTOSKELETON IN RED ALGAE USING FLUORESCENT LABELING

Cytoskeletal components have been visualized for the first time in red algae using fluorescent labelling. Rhodamine-phalloidin was used to s tain actin in a variety of filamentous species: Griffithsia pacifica, Tiffaniella snyderae, Ceramium strictum, Antithamnion kylinii (Ceramia les) and Audouinella dasyae (Acrochaetiales). immunofluorescent labell ing of microtubules was obtained only in Griffithsia pacifica. In both procedures, successful labelling was achieved only after wall digesti on with glucuronidase and protocols using cellulase resulted in no lab elling. Both microfilaments and microtubules formed extensive arrays i n the peripheral cytoplasm of Griffithsia. Microtubules were associate d with nuclei in these highly multinucleate cells, suggesting that the y maintain the extremely regular nuclear arrangement. Dense labelling of microfilaments occurred at rhizoid apices, however, this was not ob served 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 remain ing 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. Cytoskele tal components often showed a polar distribution with denser labelling towards the bases or apices of cells. In dividing apical cells of Gri ffithsia, a band of microfilaments was observed prior to deposition of the new cross wall. These preliminary results suggest that cytoskelet al studies will provide important insights into understanding developm ent and cell function in red algae.