Involvement of Nonhistone Chromosomal Proteins in Transcriptional Activity of Chromatin during Wheat Germination

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Abstract
To clarify how the transcriptionally inactive chromatin of dormant wheat [Triticum aestivum cv. Mukakomugi] seed embryos becomes active during germination, 2 kinds of chromatin-associated proteins, histones and nonhistone proteins were studied. Two major nonhistone proteins were solubilized from purified germ chromatin with 5 M urea and were separated from histones and chromosomal RNA by Bio-Rex-70 resin and diethylaminoethyl-cellulose chromatography, respectively. Purified 5 M urea-soluble nonhistone proteins, including the 2 major nonhistone proteins, had no effect on the transcription of native wheat DNA. Two kinds of chromatins were reconstituted by gradient dialysis from a mixture of DNA, germ histones and nonhistone proteins derived from germs or germinated seedlings. Reconstituted chromatins had a 1.4- to 1.6-fold higher protein content than DNA content, protein components similar to native chromatin and had only about 17-25% and 37% the transcriptional activities of native seedling and germ chromatin, respectively. Using the transcriptional activity of chromatin reconstituted from DNA and histones alone as a standard, 1 kind of reconstituted chromatin containing nonhistone proteins of germ was only about 1/4 as active as the standard. Another with nonhistone proteins from seedlings was about 1.3-1.5 times more active than the standard. The ratio of histones to DNA content is approximately 1.3 during germination, but the proportion of histone H1 to the total histones is reduced.