USING THE DEVELOPING SPERMATOGENOUS CELLS OF CERATOPTERIS TO UNLOCK THE MYSTERIES OF THE PLANT CYTOSKELETON

The developing spermatogenous cells of Ceratopteris richardii are ideal to investigate the plant cytoskeleton. Spores sown on sterile medium produce gametophytes with antheridia at all developmental stages within a week of growth at 22 degrees C. Within an antheridium, however, all the cells are in synchrony. Other unique aspects of this system for investigation of the cytoskeleton are the structurally discernible microtubule organizing centers (MTOCs) known as the blepharoplast and multilayered structure (MLS), the de novo production of centrioles, and the production of multiflagellated sperm cells. Immunocytochemical localization studies reveal that the blepharoplast reacts with two monoclonal antibodies that recognize animal centrosomes. The lamellar strip of the MLS reacts strongly with the centrosomal protein centrin. These are the first reports of the specific localization of MTOC proteins/epitopes in structurally discernible land plant MTOCs. Several of the stable microtubule arrays, the spline, basal body, and flagella, contain acetylated tubulin, a posttranslational modification associated with stable arrays in other eukaryotes. Tyrosinated tubulin, normally associated with relatively unstable microtubules, was found in all microtubule arrays, even the stable ones. The variety of microtubule arrays, structurally discernible MTOCs, and ease of culture make the spermatogenous cells of Ceratopteris an excellent model system for investigation of the plant cytoskeleton.