Organisation of the microtubular cytoskeleton in protoplasts from Palmaria palmata (Palmariales, Rhodophyta)

Confocal laser scanning microscopy was used to investigate the threedimensional organisation of the microtubular cytoskeleton of protoplasts isolated from the cortex and medulla of the red alga Palmaria palmata. Immunofluorescence labelling revealed the presence of abundant microtubules in interphase cells. Cortexderived and medulladerived protoplasts each exhibited a distinctive arrangement of microtubules. In cortexderived protoplasts, a continuous network of cytoplasmic microtubules connected the peripheral array to the array which surrounded the single nucleus at the centre of the cell. At telophase, the microtubular cytoskeleton was reorganised into a network apparently involved in cytokinesis. In the multinucleate medulladerived protoplasts, each nucleus, located near the plasma membrane, was surrounded by microtubules. A uniformly arranged cortical array of microtubules was observed in both cortexderived and medulladerived protoplasts during interphase and we hypothesise that it likely plays a role in the biogenesis of the cell wall in red algal cells.