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ENVIRONMENTAL STRESS AND ADAPTATION TO STRESS

Strain Mechanosensing Quantitatively Controls Diameter Growth and PtaZFP2 Gene Expression in Poplar¹

INRA, UMR 547 PIAF, F–63100 Clermont-Ferrand, France; and Université Blaise Pascal, UMR 547 PIAF, F–63177 Aubière cedex, France

Mechanical signals are important factors that control plant growth and development. External mechanical loadings lead to a decrease in elongation and a stimulation of diameter growth, a syndrome known as thigmomorphogenesis. A previous study has demonstrated that plants perceive the strains they are subjected to and not forces or stresses. On this basis, an integrative biomechanical model of mechanosensing was established ("sum-of-strains model") and tested on tomato (Solanum lycopersicum) elongation but not for local responses such as diameter growth or gene expression. The first aim of this interdisciplinary work was to provide a quantitative study of the effect of a single transitory bending on poplar (Populus tremula x alba) diameter growth and on the expression level of a primary mechanosensitive transcription factor gene, PtaZFP2. The second aim of this work was to assess the sum-of-strains model of mechanosensing on these local responses. An original bending device was built to study stem responses according to a controlled range of strains. A single bending modified plant diameter growth and increased the relative abundance of PtaZFP2 transcripts. Integrals of longitudinal strains induced by bending on the responding tissues were highly correlated to local plant responses. The sum-of-strains model of mechanosensing established for stem elongation was thus applicable for local responses at two scales: diameter growth and gene expression. These novel results open avenues for the ordering of gene expression profiles as a function of the intensity of mechanical stimulation and provide a generic biomechanical core for an integrative model of thigmomorphogenesis linking gene expression with growth responses.

² These authors contributed equally to the article.

The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Catherine Coutand (coutand{at}clermont.inra.fr).

www.plantphysiol.org/cgi/doi/10.1104/pp.109.138164

^* Corresponding author; e-mail coutand{at}clermont.inra.fr.

Received March 6, 2009; accepted June 28, 2009; published July 1, 2009.

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On the Inside

Peter V. Minorsky
Plant Physiol. 2009 151: 1-2. [Full Text]