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

The distribution of acetylated tubulin in microtubule arrays of conifer cells was investigated by immunofluorescence techniques with 6-11B-1, a monoclonal antibody specific for posttranslationally acetylated alpha-tubulins. In methacrylate sections of Pinus radiata and Pinus contorta root tip cells, acetylated tubulin was detected in mitotic spindles, phragmoplasts, and cortical microtubules. Furthermore, staining of isolated, intact cells of P. radiata and P. contorta indicated that all microtubule structures. including preprophase bands, prophase, metaphase and anaphase spindles, and phragmoplasts, contained some acetylated tubulin, and that the intensity of staining with 6-11B-1 was variable. For example, preprophase bands were lightly labelled, kinetochore fibres of anaphase spindles and phragmoplasts were heavily stained, and metaphase spindles had a granular appearance suggesting discontinuous acetylation of their constituent microtubules. This first report of the presence of acetylated tubulin in conifer cells is in contrast to our results with two species of angiosperms where no acetylated tubulin was detected. The significance of this and the variability of the intensity of staining in conifer arrays is discussed in terms of microtubule dynamics.