Protein synthesis on the cytoskeleton

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Plant Physiologists
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Abstract Number:1690

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Program Information

Session Number	Session Name
65	Late and Moved Abstracts

Presented by: Bratislav Stankovic, stankovic.1@osu.edu

Authors:


Stankovic, Bratislav	Department of Plant Biology, Ohio State University, Columbus, OH 43210, USA
Davies, Eric	Botany Department, North Carolina State University, Raleigh, NC 27695, USA
Abe, Shunnosuke	College of Agriculture, Ehime University, Tarumi, Matsuyama, Japan

Relatively little is known about the existence and possible function of cytoskeleton-bound polysomes (CBP) in plants, despite the recognition of the fundamental role of the cytoskeleton in the sub-cellular transport and localization of mRNAs in animals. However, trafficking and regulation of the translation of mRNAs on the plant cytoskeleton might be expected since it has already been shown that wound-induced inhibition and recovery in the rate of cytoplasmic streaming (an F-actin-dependent process) correlates with the inhibition and recovery in the rate of protein synthesis. Here we provide evidence from two different systems - the pea epicotyl and the maize endosperm - for the existence and function of CBP in plants. Using biochemical cell fractionation experiments in conjunction with variable-term, sucrose density gradient centrifugation, we have identified 4 distinct populations of polysomes (free-, membrane-bound-, cytoskeleton-bound-, and cytoskeleton-membrane-bound polysomes). Using in vivo and in vitro radioactive labeling, we have compared the translational efficiency of each of these populations of polysomes, in an attempt to understand whether mRNA associated with the different populations of polysomes is preferentially translated. Using fluorescence microscopy, we have shown associations between filamentous actin, polysomes and protein bodies following homogenization of corn endosperm in a cytoskeletal stabilizing buffer. Electron micrographs of tissue sections and isolated pellets processed in a variety of ways suggest the existence of abundant 4-5 nm nanofilaments in etiolated peas. The ribosomes seem to associate with these as well as with the normal microfilaments.

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