Comparative effects of phalloidin and cytochalasin B on motility and morphogenesis in Allium

Abstract

Cytochalasin B (CB), thought to disaggregate F-actin in animal cells, and phalloidin (Phal), known to stabilize F-actin in vivo and in vitro, have nearly identical effects on cotyledon epidermal cells of Allium cepa. Both drugs rapidly induce cessation of streaming and both, by preventing normal telophase reorientation movement, lead to abnormal division planes in dividing guard mother cells. Neither, however, prevents normal microtubule deposition, wall thickening, and cellulose orientation during guard cell differentiation. Furthermore, both drugs have no effect on spindle formation and anaphase chromosome motion. Examination of Nitella and Chara cells, in which streaming had been stopped by either agent, shows that microfilament cables are still present. With both drugs, the minimum effective concentrations were routinely used (CB, 2 μM; Phal, 100–200 μM). Our results are discussed in terms of the mode of action of these drugs and their possible role in host-fungus interactions. Implications for the mechanisms underlying cell plate alignment, cellulose orientation, and cytoplasmic streaming are discussed.

Somatic Cytokinesis and Pollen Maturation inArabidopsisDepend on TPLATE, Which Has Domains Similar to Coat Proteins

“…However, these plates were not rigid as in wild-type cells, and they did not always connect properly to the mother wall. Possibly, cell plates did not attach correctly to the mother wall and therefore did not mature as in wild-type cells, leading to crooked shapes, in agreement with previous reports (Palevitz, 1980;Mineyuki and Gunning, 1990).…”

“…Here, the mispositioning of cell plates during megaspore development is believed to retard or obstruct cell plate maturation (Geisler-Lee et al, 2002;Hong et al, 2003b). Cell plates that connect with the mother wall at unprepared sites seem not to flatten (Palevitz, 1980), possibly because the division zone contains some essential cell wall maturation factors (Mineyuki and Gunning, 1990). The embryonal cytokinesis defects in knolle and keule mutants do not display the accumulation of ectopic callose (Nickle and Meinke, 1998).…”

Microtubule and actin filament organization during stomatal morphogenesis in the fern Asplenium nidus. II. Guard cells

“…However, the fact that cytochalasin B and C does not affect the pattern of MT organization in GCs (Palevitz & Hepler, 1976 ;Palevitz, 1980 ;Marc & Palevitz, 1990) is in opposition to this hypothesis. The possibility of the involvement of the cortical AF ' systems ' in the distribution of the cortical endoplasmic reticulum, as in the case of other cell types (Hepler et al, 1990), should be also considered.…”

Possible Involvement of Calmodulin and the Cytoskeleton in Electrofusion of Plant Protoplasts

“…Calmodulin (7,9,22) and cytoskeletal elements such as microfilaments (1 1,19,25,28) and microtubules ( 13,25,26) also are present in plant cells. The cytoskeletal elements are believed to be involved in certain motile phenomena and the organization of the plasma membrane (1 [1][2][3][4][5][6][7][8][9][10][11][12][13]19), and their functions may be Ca2"-dependent (15). We have also suggested the possible contribution of Ca2+-dependent system to the membrane organization of plant protoplasts (1).…”