[Inhibition of root formation by acidic and neutral proteins from chromatin]

Abstract

An acidic (Fs) and a nearly neutral (Fn) protein fraction were extracted from the chromatin of calf thymus and pea seedlings. Both fractions are able to combine with protein-free DNA to form a complex, which, however, has a lower thermal stability than a DNA-histone complex. Fs and Fn inhibit root initiation in a similar manner as histone, actinomycin-D, streptomycin and 5-bromouracil do when these substances are applied to regenerating pea epicotyls during different times after culture initiation.Oxidized and thermally denaturated Fs and Fn inhibit root initiation less than untreated proteins do. Furthermore the treated proteins act in a more specific way on special steps of development such as root differentiation or root growth. In a very similar manner inhibition of root regeneration is also restricted to special developmental steps by treatment of Fs or Fn with small amounts (1 μg/ml) of IAA, GS or KI at pH≧8. With increasing acidity of the chromatin proteins treatment with IAA diminishes the inhibition of root growth, whereas root differentiation is preserved.The results support the suggestion that acidic and neutral proteins of the chromatin may act as regulators of DNA-activity as histone does. During IAA-induced root formation Fs acts as an antagonist to histone, because these two protein fractions are specialized in their action by IAA treatment in a contrary manner.