Plasma membrane-cell wall connections: Roles in mitosis and cytokinesis revealed by plasmolysis ofTradescantia virginiana leaf epidermal cells

Abstract

Tradescantia virginiana leaf epidermal cells were plasmolysed by sequential treatment with 0.8 M and 0.3 M sucrose. Plasmolysis revealed adhesion of the plasma membrane to the cell wall at sites coinciding with cytoskeletal arrays involved in the polarisation of cells undergoing asymmetric divisions--cortical actin patch--and in the establishment and maintenance of the division site--preprophase band of microtubules and filamentous (F) actin. The majority of cells retained adhesions at the actin patch throughout mitosis. However, only approximately 13% of cells formed or retained attachments at the site of the preprophase band. After the breakdown of the nuclear envelope, plasmolysis had a dramatic effect on spindle orientation, cell plate formation, and the plane of cytokinesis. Spindles were rotated at abnormal angles including tilted into the plane of the epidermis. Cell plates formed but were quickly replaced by vacuole-like intercellular compartments containing no Tinopal-stainable cell wall material. This compartment usually opened to the apoplast at one side, and cytokinesis was completed by the furrow extending across the protoplast. This atypical cytokinesis was facilitated by a phragmoplast containing microtubules and F-actin. Progression of the furrow was unaffected by 25 micrograms of cytochalasin B per ml but inhibited by 10 microM oryzalin. Phragmoplasts were contorted and misguided and cytokinesis prolonged, indicating severe disruption to the guidance mechanisms controlling phragmoplast expansion. These results are discussed in terms of cytoskeleton-plasma membrane-cell wall connections that could be important to the localisation of plasma membrane molecules defining the cortical division site and hence providing positional information to the cytokinetic apparatus, and/or for providing an anchor for cytoplasmic F-actin necessary to generate tension on the phragmoplast and facilitate its directed, planar expansion.

Hyperosmotically induced accumulation of a phosphorylated p38‐like MAPK involved in protoplast volume regulation of plasmolyzed wheat root cells

“…cytoskeleton reorganization and protoplast volume regulation In plants, hyperosmotic stress induces massive reorganization of the tubulin and actin cytoskeleton [13,14,[22][23][24][25]. In wheat root cells, Mts are disintegrated and replaced by tubulin macrotubules [13].…”

Cortical division zone establishment in plant cells

“…In view of an important role for the PM, we might need to look for membrane-anchored proteins that are under mitotic control. In Tradescantia and BY-2 cells, an abundance of PM-cell wall connections have been visualized at the division zone [31,33]. PM-cell wall linker proteins could help to maintain the putative mark required for division zone specification at the correct position ( Figure 2).…”

“…The positional information laid down by the PPB resists mechanical stresses such as centrifugation, but is disturbed by wounding of the putative division zone using a microneedle [29,30]. Moreover, plasmolysis or treatment of dividing cells with DMSO or methanol lead to an increase in the percentage of cells carrying obliqueoriented cell plates [30,31]. These observations suggest that the integrity of the PM and/or the PM-to-cell wall connection is vital for the maintenance of the cortical positional information.…”

Plant cortical microtubule dynamics and cell division plane orientation

“…Higher plants establish a highly ordered array of microtubules at cell cortex, and the orientation of the division plane follows the orientation of the cortical microtubule array. The preprophase band (PPB), a dense ring of microtubules formed through the aggregation of the oriented sparse array of the cortical microtubules predicts the insertion site of the new division plane (Vos et al, 2004;Cleary, 2001;Dixit and Cyr, 2002;Mineyuki, 1999;Molchan et al, 2002;Pickett-Heaps et al, 1999;Valster et al, 1997). It has been recognised that this is an important clue towards the molecular understanding of oriented cell division in plant cell (Staehelin and Hepler, 1996).…”

“…The PPB plays a key role in determining the exact location (determining factor of symmetric/asymmetric division) of the division plane. During spindle formation and nuclear membrane breakdown, the PPB is also broken down, leaving behind a spatial marker for the correct insertion of the cell plate (Lloyd and Buschmann, 2007;Wright et al, 2009;Cleary, 2001;Dixit and Cyr, 2002;Mineyuki, 1999;Molchan et al, 2002;Pickett-Heaps et al, 1999;Valster et al, 1997). Cell divides through the formation of an outward growing cell plate that fuses with the parental plasma membrane and cell wall along the spatial signature left by the PPB (Staehelin and Hepler, 1996).…”