POSTTRANSLATIONAL TUBULIN MODIFICATIONS IN SPERMATOGENEOUS CELLS OF THE PTERIDOPHYTE CERATOPTERIS-RICHARDII

Acetylation and tyrosinization are post-translational modifications of tubulin generally associated, respectively, with highly stable or dyn amic microtubule arrays in animals and protists. Little is known of th ese modifications in land plants, however. We examined the presence an d distribution of post-translational tubulin modifications in developi ng spermatogenous cells of the pteridophyte Ceratopteris richardii by immunofluorescence and immunogold, utilizing antibodies specific for a cetylated and tyrosinated tubulin. Acetylated tubulin is found in mid to late stage spermatogenous cells in stable microtubule configuration s: the spline, flagella, and basal bodies. Tyrosinated tubulin, a modi fication associated with dynamic microtubule arrays, is also present i n these structures as well as all other microtubules in the cell. The lamellar strip of the multilayered structure, a body previously descri bed as tubulin-containing, was not labelled by any of the tubulin anti bodies or antiserum. Treatment of cultures with the microtubule stabil izer taxol results in the appearance of new arrays of microtubules, in cluding bundles in the cytoplasm. Only those new taxol-induced microtu bule arrays present in mid to late stage cells (i.e., those with other normally acetylated tubulin arrays) have acetylated domains. Younger spermatogenous cells had similar microtubule bundles but no acetylated tubulin. Tyrosinated tubulin was found in all these taxol-stabilized arrays. These data indicate that, although these pteridophyte cells ha ve the ability to acetylate tubulin, that this ability is limited to s tages after the final spermatogenous cell mitosis and is limited to th e highly stable spline and flagella microtubules.