[Possibilities of the regulation of differential DNA activities in higher plants by histone].

By staining calf-thymus histones with fluorescein isothiocyanate and by diazotation it could be shown that externally applied histones enter the cells and accumulate specially in the nucleus. The permeability of the cell membranes does not increase upon application of 100 μg/ml calf-thymus histone (the calf-thymus histone is soluble to less than 50% in water) as measurements of the betacyanin-efflux in tissues of the red beet showed. Application of actinomycin D and calf-thymus histone during the first days of culture (24-72 hrs after culture initiation) inhibits root formation and root growth without diminishing the number of newly formed spots of embryonic cells. Externally applied histone therefore with high probability intervenes mostly in the nucleic acids of the cells.The inhibition of root formation, of differentiation of tracheae and of root growth shows no specific differences upon application of histone from calf-thymus glands or from pea epicotyls or of protamine or poly-1-lysine.With increasing concentration of histone the inhibition of root formation occured over a longer period. After the percentage of free NH2-groups had been diminished by gently acetylation and after the secondary structure had been altered by thermal denaturation of histones, the inhibition of root formation and differentiation of tracheae decreased strongly. The inhibition of root growth, however, still remained. Thermally denatured protamine inhibited root formation and root growth over a longer period than untreated protamine did. The performed acetylation and thermal denaturation hardly lessened the binding capacity of histone to DNA. It is assumed that changes in the histone content of the cells as well as little alterations of histone binding capacity to DNA may play an important role in the regulation of some differential DNA activities by histones and perhaps by other basic proteins.