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Comment
. 2010 Jun;5(6):752-4.
doi: 10.4161/psb.5.6.11706. Epub 2010 Jun 1.

Cortical microtubules are responsible for gravity resistance in plants

Takayuki Hoson  1 , Shouhei Matsumoto, Kouichi Soga, Kazuyuki Wakabayashi
Affiliations
Comment

Cortical microtubules are responsible for gravity resistance in plants

Takayuki Hoson et al. Plant Signal Behav. 2010 Jun.

Abstract

Mechanical resistance to the gravitational force is a principal gravity response in plants distinct from gravitropism. In the final step of gravity resistance, plants increase the rigidity of their cell walls. Here we discuss the role of cortical microtubules, which sustain the function of the cell wall, in gravity resistance. Hypocotyls of Arabidopsis tubulin mutants were shorter and thicker than the wild-type, and showed either left-handed or right-handed helical growth at 1 g. The degree of twisting phenotype was intensified under hypergravity conditions. Hypergravity also induces reorientation of cortical microtubules from transverse to longitudinal directions in epidermal cells. In tubulin mutants, the percentage of cells with longitudinal microtubules was high even at 1 g, and it was further increased by hypergravity. The left-handed helical growth mutants had right-handed microtubule arrays, whereas the right-handed mutant had left-handed arrays. Moreover, blockers of mechanoreceptors suppressed both the twisting phenotype and reorientation of microtubules in tubulin mutants. These results support the hypothesis that cortical microtubules play an essential role in maintenance of normal growth phenotype against the gravitational force, and suggest that mechanoreceptors are involved in signal perception in gravity resistance. Space experiments will confirm whether this view is applicable to plant resistance to 1 g gravity, as to the resistance to hypergravity.

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Figures

Figure 1
Figure 1
Mechanism of gravity resistance in plants. The gravity signal is perceived by the mechanoreceptors located on the plasma membrane, and then transformed and transduced into the cells. The transduced signal induces the expression of diverse genes and influences the structure and function of various cellular components. Cortical microtubules, in concert with the plasma membrane, regulate the cell wall metabolism as well as apoplastic environment, leading to an increase in the cell wall rigidity.
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References

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