Cytoskeletal elements and their involvement in Polyphysa (acetabularia) protoplast differentiation : Cytoskeleton modifiers and concanavalin A-mediated effects

Protoplasts from coenocytic cap rays of the marine green alga Polyphysa (Acetabularia) cliftonii were treated with microtubule- (colchicine) and microfilament modifiers (cytochalasin A and B), to examine the involvement of cytoskeletal elements in gametangial morphogenesis as well as the presence or absence of a cytoskeletal transmembrane control of concanavalin A (ConA) receptors. The antitubulin inhibits mitosis, disrupts the anchorage of the nuclei and prevents the demarcation of the lid in the gametangial wall, but induces fluorescence-detectable ‘pre-lids’. It does not interfere with the partitioning of coenocytic protoplasts into uninucleate protoplasts, with the development of gametangial shape, and with the initiation of cellulosic walls. Cytochalasins suppress protoplasmic cleavage, reduce mitotic division and lead to the occurrence of ‘twin’ nuclei. They do not prevent cellulosic wall formation and the expression of lids. The combined effects of either colchicine or cytochalasins with ConA are cumulative. It is concluded that microtubules or microfilaments are not directly involved in cell wall initiation and synthesis, and furthermore, exert no direct transmembrane control on the exposure of ConA receptors, or ConA receptor binding.