The role of the microtubular cytoskeleton in determining nuclear chromatin structure and passage of maize root cells through the cell cycle.

Depolymerization of microtubules in metabolically inactive quiescent center (QC) cells of maize root apices by means of three different antimicrotubular treatments (colchicine, oryzalin and low temperature) elicited very similar responses in their nuclei. Conspicuous nuclear enlargement was closely associated with chromatin decondensation and accelerated traverse of their cell cycle. This latter finding was inferred not only from cytophotometry which showed an increased proportion of S and G2 nuclei in this group of cells, but also from autoradiography which confirmed the greater proportion of nuclei engaged in the S phase of the cell cycle. Activation of the QC cells with various antimicrotubular agents may be a reflection of a dependency of nuclear cell cycle events on the turnover of cytoplasmic microtubules during interphase. The nuclear size, nuclear chromatin structure, as well as cell cycle progression, seem to be regulated by the dynamic nature of the microtubular cytoskeleton.