Plant Cell Growth Responds to External Forces and the Response Requires Intact Microtubules

Abstract

Microfibril deposition i n most plant cells i s influenced by cortical microtubules. Thus, cortical microtubules are templates that provide spatial information to the cell wall. How cortical microtubules acquire their spatial information and are positioned is unknown. There are indications that plant cells respond to mechanical stresses by using microtubules as sensing elements. Regenerating protoplasts from tobacco (Nicotiana tabacum) were used to determine whether cells can be induced t o expand in a preferential direction in response to an externally applied unidirectional force. Additionally, an anti-microtubule herbicide was used t o investigate the role of microtubules in the response to this force. Protoplasts were embedded i n agarose, briefly centrifuged at 28 to 34g, and either cultured or immediately prepared for immunolocalization of their microtubules. The microtubules within many centrifuged protoplasts were found t o be oriented parallel t o the centrifugal force vector. Most protoplasts elongated with a preferential axis that was oriented 60 t o 90" t o the applied force vector. Protoplasts treated transiently with the reversible microtubule-disrupting agent amiprophos-methyl (applied before and during centrifugation) elongated but without a preferential growth axis. These results indicate that brief biophysical forces may influence the alignment of cortical microtubules and that microtubules themselves act as biophysical responding elements.

Activation of plasma membrane voltage‐dependent calcium‐permeable channels by disruption of microtubules in carrot cells

“…Immunocytochemical staining of microtubules showed that control protoplasts displayed randomly oriented cortical microtubules as already described [30] (Fig. 2A).…”

The Transcript Level of Katanin Gene is Increased Transiently in Response to Changes in Gravitational Conditions in Azuki Bean Epicotyls

“…The orientation of cortical microtubules is under the control of environmental signals, such as gravity. For example, hypergravity promoted reorientation of microtubules into parallel arrays in protoplasts from Nicotiana tabacum (Wymer et al, 1996) and Brassica napus (Skagen and Iversen, 1999). Also, hypergravity induced reorientation of cortical microtubules from transverse to longitudinal directions in azuki bean epicotyls (Soga et al, 2006).…”

Alteration of Microtubule Dynamic Instability during Preprophase Band Formation Revealed by Yellow Fluorescent Protein–CLIP170 Microtubule Plus-End Labeling[W]

“…Unlike other eukaryote cells, vacuolated and cell wall-confined plant cells follow a specialized mode of cytokinesis, exhibiting four major microtubular arrays at different cell cycle stages with a variety of functions (Goddard et al, 1994). During interphase, a cortical array consisting of parallel microtubules oriented perpendicular to the cell expansion axis assists cellulose deposition (Cyr, 1994) and responds to stimuli (Wymer et al, 1996). At the onset of mitosis, the cortical array is replaced by a densely packed ring of microtubules encircling the nucleus called the preprophase band (PPB), which defines the location of the cell plate formed during cytokinesis (Mineyuki, 1999).…”