Acetylated tubulin is found in all microtubule arrays of two species of pine

The distribution of acetylated tubulin in microtubule arrays of conifer cel ls was investigated by immunofluorescence techniques with 6-11B-1, a monocl onal antibody specific for posttranslationally acetylated alpha-tubulins. I n methacrylate sections of Pinus radiata and Pinus contorta root tip cells, acetylated tubulin was detected in mitotic spindles, phragmoplasts, and co rtical microtubules. Furthermore, staining of isolated, intact cells of P. radiata and P. contorta indicated that all microtubule structures. includin g preprophase bands, prophase, metaphase and anaphase spindles, and phragmo plasts, contained some acetylated tubulin, and that the intensity of staini ng with 6-11B-1 was variable. For example, preprophase bands were lightly l abelled, kinetochore fibres of anaphase spindles and phragmoplasts were hea vily stained, and metaphase spindles had a granular appearance suggesting d iscontinuous acetylation of their constituent microtubules. This first repo rt of the presence of acetylated tubulin in conifer cells is in contrast to our results with two species of angiosperms where no acetylated tubulin wa s detected. The significance of this and the variability of the intensity o f staining in conifer arrays is discussed in terms of microtubule dynamics.