LOCALIZATION OF THE FUNCTIONAL P34(CDC2) HOMOLOG OF MAIZE IN ROOT-TIPAND STOMATAL COMPLEX CELLS - ASSOCIATION WITH PREDICTED DIVISION SITES

We have used an antibody against the functional homolog of the cdc2 ki nase of maize to localize the p34cdc2 protein within dividing cells of the root apex and the stomatal complex of leaf epidermis. The microtu bule cytoskeletal structure of plant cells was visualized concomitantl y with a monoclonal antibody specific for alpha-tubulin. We found that the cdc2 protein is localized mainly to the nucleus in plant cells at interphase and early prophase. This finding contrasts markedly with t he predominantly cytoplasmic staining obtained using antibody to the P STAIRE motif, which is common to cdc2 and numerous cdc2-like proteins. In a subpopulation of root cells at early prophase, the p34cdc2 prote in is also distributed in a band bisecting the nucleus. Double labelin g with the maize p34cdc2ZM antibody and tubulin antibody revealed that this band colocalizes with the preprophase band (PPB) of microtubules , which predicts the future division site. Root cells in which microtu bules had been disrupted with oryzalin did not contain this band of p3 4cdc2 protein, suggesting that formation of the microtubule PPB is nec essary for localization of the p34cdc2 kinase to the plane of the PPB. The p34cdc2 protein is also localized to the nucleus and PPB in cells that give rise to the stomatal complex, including those cells prepari ng for the highly asymmetrical divisions that produce subsidiary cells . Association of the p34cdc2 protein with the PPB suggests that the cd c2 kinase has a role in establishing the division site of plant cells and, therefore, a role in plant morphogenesis.