Patterns of microtubule organization in two polyhedral cell types in the gametophyte of the liverwort Marchantia paleacea Bert.

Abstract

SUMMARYTbe typical scale cells (TSCs) of Marchantia paleacea Bert, contain a well-developed cortical microtubule (Mt) cytoskeleton, particularly below tbe anticlinal walls and also display complete but broad prepropbase-propbase Mt bands (PMBs). In contrast, tbe cortical cytoskeleton of the inner tballus cells (ITCs) is less developed tban that of TSCs and tbe PMBs are incomplete. Tbe latter consist of one to four separate Mt bundles wbicb lie on tbe cytokinetic plane, but do not form a complete Mt ring. In botb cell types PMB formation precedes or keeps pace with the activation of the polar Mt-organizing centres (MTOCs) and nuclear shaping. The Mts in the PAiBs are more numerous and densely packed at the cell edges tban on the cell face. The polar MTOCs persist up to late prophase-prometaphase. Afterwards, the spindle Mts are focused on several minipoles, where endoplasmic reticulum is localized. In postcytokinetic cells the cortical Mts first reappear on the daughter wall surface.Our findings suggest that: {a) The formation of complete or incomplete PMBs in TSCs and ITCs of M. paleacea is related to differences in the development of the interphase cortical Mt arrays. (6) Tbe cell edges are able to form or at least arrange the Mts of the PMB. (c) Tight mature PMBs like those found in flowering plant cells are not formed in the cells examined in the present study, {d) The final orientation of tbe cell plate is controlled by the PMB cortical zone, (e) The cytoplasm abutting on the postcytokinetic daughter wall has the ability to assemble cortical Mts.

Aluminium Effects on Microtubule Organization in Dividing Root-Tip Cells of Triticum turgidum. II. Cytokinetic Cells

“…This may suggest that the cortical cytoplasm in post-telophase cells of higher plants has the ability to polymerize tubulin (see also Galatis and Apostolakos 1991a, Panteris et a/. 1991, 1995, Apostolakos and Galatis 1992.…”

Interphase and preprophase microtubule organization in some polarized cell types of the liverwort Marchantia paleacea Bert.

“…interphase cortical microtubules (Apostolakos & Galatis, 1992). In other words, there appears to be sufficient tubulin for both preprophase-prophase microtubule systems.…”

“…In these cells the edges of the cell plate follow a curved path of growth to find the cortical zone marked by the PPB. Therefore, in the cell types studied here, as well as in typical scale and inner thallus cells of M. paleacea (Apostolakos & Galatis, 1992), the PPB cortical zone behaves in a way similar to higher plant cells (Galatis, Apostolakos & Katsaros, 1983, 1984a; see also Gunning & Wick, 1985;Baskin & Cande, 1990;Wick, 1991a, 6). Moreover, the polarization of the cortical cytoplasm also explains the formation of the S-like daughter walls, laid down in certain dividing protodermal cells of M. paleacea (Apostolakos & Galatis, 19856, c).…”

“…In M. paleacea, certain epidermal cell types (Apostolakos & Galatis, 1985 6), inner thallus cells (Apostolakos & Galatis, 1992) and some PFCs (this work) exhibit interrupted PPBs. In contrast, typical scale cells (Apostolakos & Galatis, 1992), PFMCs and MPMCs (this work) show complete PPBs. In PFMCs and MPMCs the plane of cytokinesis is predicted by the interphase microtubule ring.…”

“…Some cortical microrings (Apostolakos & Galatis, 19856, 1992. In tubules persist during mitosis (literature in contrast, typical scale cells form complete PPBs Schnepf, 1983Schnepf, , 1986Doonan & Duckett, 1988; (Apostolakos & Galatis, 1992). Boppe?…”