In touch: plant responses to mechanical stimuli.

Summary 1I. Introduction 2II. Fast and fascinating– thigmonasty and thigmotropism 2III. Subcellular touch-induced movements 10IV. Thigmomorphogenesis 10V. Discovery of theArabidopsis TCHgenes 12VI. Microarray identification of touch-inducible genes 12VII. Regulation ofTCHgene expression 13 Acknowledgements 14 References 14Perception and response to mechanical stimuli are likely essential at the cellular and organismal levels. Elaborate and impressive touch responses of plants capture the imagination as such behaviors are unexpected in otherwise often quiescent creatures. Touch responses can turn plants into aggressors against animals, trapping and devouring them, and enable flowers to be active in ensuring crosspollination and shoots to climb to sunlit heights. Morphogenesis is also influenced by mechanical perturbations, including both dynamic environmental stimuli, such as wind, and constant forces, such as gravity. Even individual cells must sense turgor and wall integrity, and subcellular organelles can translocate in response to mechanical perturbations. Signaling molecules and hormones, including intracellular calcium, reactive oxygen species, octadecanoids and ethylene, have been implicated in touch responses. Remarkably, touch-induced gene expression is widespread; more than 2.5% ofArabidopsisgenes are rapidly up-regulated in touch-stimulated plants. Many of these genes encode calcium-binding, cell wall modifying, defense, transcription factor and kinase proteins. With these genes as tools, molecular genetic methods may enable elucidation of mechanisms of touch perception, signal transduction and response regulation.New Phytologist(2004)doi: 10.1111/j.1469-8137.2004.01263.x© New Phytologist(2004) [ABSTRACT FROM AUTHOR]