Phosphorylation of Chromosomal Proteins in Resting and Wounded Potato Tuber Tissues

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Wounding of quiescent white potato tuber tissue enhances chromatin-bound protein phosphokinase activity, which exhibits two distinct phases during wound-healing. A moderate activation of the enzymes up to 20 hr after injury is followed by a dramatic increase in activity with a peak at 50 hr. This time-course resembles that of chromatin-bound DNA-dependent RNA polymerase with a peak in activity at about 48 hr after wounding. The kinases phosphorylate endogenous proteins as well as added histones, phosvitin and casein. The incorporated phosphate is stable under standard assay conditions. indicating the absence of protein phosphatases. Sensitivity of the incorporated phosphate toward trypsin and alkali, but not DNase, RNase, hydroxylamine or succinic acid points to seryl- and threonyl-bonds and proteins as acceptor molecules. Kinases from resting tissues are only weakly stimulated even by 100 mM MgCl_2, those from wounded tissues exhibit pronounced Mg^<++>_optima at 5-1O mM with endogenous proteins, phosvitin and casein and 50 mM MgCl_2 with histones. Wounding also increases the sensitivity of the kinases toward p-hydroxymercuribenzoate. Chromatin preparations from both resting and wounded tissues contain about 40 protein bands after polyacrylamide disc gel electrophoresis. In vitro phosphorylation of these proteins in chromatin from quiescent tissues is comparably low and uniform. Wounding induces changes in the protein and phosphorylation pattern with a general enhancement of phosphorylative capacity and preferential phosphorylation of low molecular weight proteins.
日本植物生理学会の論文

Phosphorylation of Chromosomal Proteins in Resting and Wounded Potato Tuber Tissues

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