Field emission scanning electron microscopy of microtubule arrays in higher plant cells

Abstract

Specimen preparation protocols that allow field emission scanning electron microscope imaging of microtubules in plant cells were developed, involving simultaneous permeabilization with saponin and stabilization of microtubules with taxol. All categories of microtubule array were observed in onion root tip cells and in tobacco BY-2 cells grown in suspension culture and synchronized to provide high frequencies of mitotic stages. Cortical arrays consist of overlapping microtubules with free ends; individual microtubules directly overlie individual microfibrils in the cell wall. Preprophase bands and spindle microtubule bundles were also imaged. Phragmoplasts revealed early stages of wall deposition in the included cell plates and features interpreted as relating to high rates of microtubule turnover at the growing margins. It was possible to combine high resolution three-dimensional imaging with immunogold labelling of microtubules. Individual gold particles were readily distinguished decorating microtubules in the preparations; the method should be vaulable for studying many features of plant cell microtubules and their associated macromolecules.