QUANTIFICATION OF MICROTUBULE DYNAMICS IN LIVING PLANT-CELLS USING FLUORESCENCE REDISTRIBUTION AFTER PHOTOBLEACHING

Microtubule (MT) turnover within the four principal MT arrays, the cor tical array, the preprophase band, the mitotic spindle and the phragmo plast, has been measured in living stamen hair cells of Tradescantia. that have been injected with fluorescent neurotubulin. Using the combi ned techniques of confocal laser scanning microscopy and fluorescence redistribution after photobleaching (FRAP), we report that the half-ti me of turnover in spindle MTs is t(1/2)=31+/-6 seconds, which is in ex cellent agreement with previous measurements of turnover in animal cel l spindles. Tradescantia interphase MTs, however, exhibit turnover rat es (t(1/2)=67+/-seconds) that are some 3.4-fold faster than those meas ured in interphase mammalian cells, and thus are revealed as being hig hly dynamic. Preprophase band and phragmoplast MTs have turnover rates similar to those of interphase MTs in Tradescantia. The spatial and t emporal aspects of the fluorescence redistribution after photobleachin g in all four MT arrays are more consistent with subunit exchange by t he mechanism of dynamic instability than treadmilling. This is the fir st quantification of MT dynamics in plant cells.