Chapter

Mechanical Integration of Plant Cells and Plants

Volume 9 of the series Signaling and Communication in Plants pp 53-90

Date:

Mechanics of the Cytoskeleton

  • Peter NickAffiliated withBotanical Institute and Center of Functional Nanostructures, Karlsruhe Institute of Technology Email author 

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Abstract

This chapter summarizes evidence for a cytoskeletal function in tensegral integration on both the organismal and the cellular levels. The plant cytoskeleton consists of two major elements, microtubules and actin filaments. The spatial organization of these elements is highly dynamic and changes fundamentally during the cell cycle, with conspicuous effects on the predicted stress–strain patterns. In interphase cells, microtubule bundles are thought to control the direction of cellulose deposition and thus to reinforce the axiality of cell growth. By microtubule–actin linkers such as the novel class of plant-specific kinesins with a calponin-homology domain, the rigid microtubules and the flexible actin bundles can be integrated into a system endowed with mechanical tensegrity. Because the plant cytoskeleton is relieved of the load-bearing task it fulfils in the non-walled animal cells, it has adopted sensory functions. Stretch-induced changes of protein conformation and stretch-activated ion channels seem to act in concert with the cytoskeleton, which acts either as a stress-focussing susceptor of mechanical force upon mechanosensitive ion channels or as a primary sensor that transduces mechanical force into differential growth of microtubule plus ends. This cytoskeletal tensegrity sensor is used both to integrate the growth of individual cells with mechanical load of tissues and organs and as an intracellular sensor used to control holistic properties of a cell such as organelle positioning. The distinct nonlinearity of microtubules in particular renders them an ideal tool for self-organization in response to mechanical input from the exterior.