Responses of chrysanthemum cells to mechanical stimulation require intact microtubules and plasma membrane-cell wall adhesion

Plant cells are highly susceptible and receptive to physical factors, both in nature and under experimental conditions. Exposure to mechanical forces dramatically results in morphological and microstructural alterations in their growth. In the present study, cells from chrysanthemum (Dendranthema morifolium) were subjected to constant pressure from an agarose matrix, which surrounded and immobilized the cells to form a cell-gel block. Cells in the mechanically loaded blocks elongated and divided, with an axis preferentially perpendicular to the direction of principal stress vectors. After a sucrose-induced plasmolysis, application of peptides containing an RGD motif, which interferes with plasma membrane-cell wall adhesion, reduced the oriented growth under stress conditions. Moreover, colchicines, but not cytochalasin B, abolished the effects of mechanical stress on cell morphology. Cellulose staining revealed that mechanical force reinforces the architecture of cell walls and application of mechanical force, and RGD peptides caused aggregative staining on the surface of plasmolyzed protoplasts. These results provide evidence that the oriented cell growth in response to compressive stress requires the maintenance of plasmalemma-cell wall adhesion and intact microtubules. Stress-triggered wall development in individual plant cells was also demonstrated.