XVI International Botanical Congess

Descendant cells of meristems stop dividing and differentiate or, as illustrated by the pericycle, divide again in response to appropriate stimuli. What causes some pericycle cells to divide and others to remain quiescent ? Auxin is a signal but what is the mechanism of activation ? We tested the hypothesis that a cell sizer control is a component by expressing a fission yeast cell size regulatory gene, cdc25 in tobacco. Under an inducible promoter, cdc25 expression results in small primordia, in greater frequency and exhibiting smaller cell size at division compared with uninduced controls. The data are consistent in showing that perturbation of cell size coincides with a greater frequency of laterals. The hypothesis is that the fission yeast cdc25 interacts with the plant cell cycle to induce this change in morphogenesis.