Studies of chromatin from normal and crown gall tumor tissue cultures of tobacco

Abstract

The T m, the DNA: histone: residual protein ratios, RNA-polymerase activity and template activity of chromatin from normal and bacteria-free crown gall tumor tissue cultures of tobacco (cv. Wisconsin 38) were very similar. Template activity of unsheared chromatin, which was about one-tenth that of DNA, was nearly doubled on shearing. In comparison with normal tissue, the tumor tissue was much lower in soluble and chromatin-associated RNase, DNase and protease activity. The amounts of lysine-rich (F I), moderately lysinerich (F II) and arginine-rich (F III) histone fractions, respectively, were 92, 5·3 and 2·8% for the normal tissue, and 87, 10·2 and 2·9% for the tumor tissue. No significant differences between normal and tumor tissue were noted in the amino acid composition of the histone or non-histone protein fractions. It is suggested that cellular transformation by crown gall bacteria may not involve derepression of the host genome. The integration of the bacterial genome into the host genome (demonstrated elsewhere) could confer on the host cell the ability to produce auxin, cytokinin and other limiting factors, and thus transform it into a tumor cell.