TISSUE-SPECIFIC AND DEVELOPMENT-SPECIFIC DISTRIBUTION OF PSTAIR-PROTEINS IN CELLS OF CONTROL AND WOUNDED MAIZE ROOT APICES

In order to study a possible involvement of cdc-like protein kinases i n cell development and tissue differentiation, a polyclonal antibody r aised against the evolutionary conserved PSTAIR-region of p34(cdc2)-ho mologue protein kinases (PSTAIR-proteins) was applied to sections of t he maize root apices, PSTAIR-proteins were localized in the nuclei and the cytoplasm of cells in the root meristem, including the quiescent centre (QC), and of all dividing cells that form the lateral root prim ordia, In most root tissues, the amount of cytoplasmic PSTAIR-proteins progressively declined with increasing distance from the root cap jun ction, becoming restricted to the nucleus after the cessation of cell divisions, This occurred much nearer to the root cap junction in cells of the stele, especially in metaxylem cells, than in cells of the roo t cortex, Interesting exceptions were cells of the pericycle, endoderm is and the outermost cell rows of stelar parenchyma, which exhibited r elatively high levels of the cytoplasmic PSTAIR-proteins throughout al l developmental zones. After root wounding, rapid cytoplasmic accumula tion of PSTAIR-proteins in cells adjacent to the wound was observed in all tissues of the meristem and of the elongation zone, This wound re sponse, which was usually followed by newly-induced cell divisions, wa s delayed with increasing distance from the root cap junction in a tis sue-specific manner, Since PSTAIR-proteins were found in the cell nucl ei throughout all developmental zones, they seem to have some nuclear functions which continue even after cell division has stopped.