Reduced Stability of Chromatin Structure of Pea Roots Grown under Calcium Starvation

The growth of pea seedlings was reduced markedly when Ca2+ was omitted from the culture medium. Some properties of chromatin from pea roots cultured with a complete supply of nutrients or a medium lacking Ca2+ were compared. Tm of the control chromatin from Ca2+-supplied plants was higher than that of the chromatin from Ca2+-deficient plants. Addition of EGTA or EDTA to control chromatin shifted its Tm to a lower temperature concomitant with an increase of hyperchromicity. The chromatin prepared from Ca2+-deficient plants was more susceptible to DNase I and II digestion. When solubilized chromatin was digested with a certain amount of DNase II and chromatographed with Bio-Gel A5m column, it turned out that digestion of the chromatin from Ca2+-deficient plants progressed more than that of the control chromatin. Template activity of the chromatin prepared from Ca2+-deficient plants was higher than that of the control chromatin, suggesting that unspecific transcription might be induced by relaxation of the chromatin structure due to Ca2+ deficiency. The Ca2+ contents of nuclear fractions were considerably lower in the Ca2+-deficient roots than in the control roots. The results suggest that differences in Ca2+ nutrition can alter chromatin structure.