PHOSPHORYLATION OF NUCLEAR PROTEINS AND PROLIFERATION IN ROOT-MERISTEMS OF PEA (PISUM-SATIVUM)

Protein kinase(s) and related endogenous substrates are present in nuclei of meristematic and adult root tissue of pea (Pisum sativum L., cv. Lincoln). The protein kinase(s) is bound to the chromatin and is not solubilized by 0.14 M NaCl, although such a salt concentration solubilizes a considerable number of endogenous substrates. Comparison of the electrophoretic patterns of phosphorylated nuclear proteins purified from quiescent or actively proliferating meristematic root tissue reveals the existence of variations of phosphorylation. Differences exist also between the electrophoretic patterns of phosphorylated nuclear proteins extracted from differentiated or meristematic root tissue. The hypothesis that the variations of phosphorylation of particular proteins might be correlated with the state of proliferation and differentiation of the cell is presented.