Untersuchungen am Chromatin der Wurzelspitze von Zea mays L.: II. Zur quantitativen Relation der Histonfraktionen im dichten und diffusen Chromatin successiver Wurzelspitzenzonen

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Summary Compact and diffuse chromatin isolated from meristem, elongation zone, and differentiated tissue of primary root tips ot two maize varieties essentially contains the same fractions of histones, as shown by electrophoresis in polyacrylamide gels. A very small quantity of a new distinct histone band is found in compact and diffuse chromatin of the meristem. It may be that it is a phosphorylated form of histone f2a2, which has been found by others during mitosis and the S-Phase of animal cells. The percentage of histone f1 is low in the diffuse chromatin of all root tip zones and also different in the two varieties investigated. In our opinion, this is a negative correlation between the content of histone f1 and the level of RNA synthesis. Proteolysis of histone f1 is suggested as mechanism which may regulate the content of histone f1 in chromatin and thus the level of RNA synthesis but not template activity. Quantitative changes within the group of slightly lysine-rich histones have also been observed, but they are beyond quantitative determination. Nevertheless, we could show that these changes are related to the level of RNA synthesis of the chromatin. All minor changes of histone pattern are connected with structural changes of chromatin and not with changes of differential gene activity. Thus the function of histones may be primarily considered as a structural one.