| RNA synthesizing activity of wheat chromatin from germinating
embryos and aleurone layers H. FUKASAWA Department of Biology, Faculty of Science, Kobe University, Kobe, Japan It has been assumed that embryonic cells have many sistes of gene activation while differentiated cells have only limited sites. In this point of view it is interesting to compare the chromatin properties between wheat germinating embryos and aleurone cells. Aleurone cells have differentiated extremely and do not divide any more, but have considerably high activity of RNA synthesis. The present preliminary report deals with the RNA synthesizing activity of chromatin prepared from germinating embryos and aleurone layers by DNA-dependent RNA polymerase obtained from Escherichia coli. Seeds of Triticum aestivum (Cultivar. Shirasagi) were germinated in dark at 25C. After 40 h incubation, embryos and endosperm portions were separated each other. Chromatin preparation followed essentially the method of SHIN and BONNER (1969). DNA was isolated according to MARMUR (1961) from 3-day-old seedlings. Template activity of chromatin or DNA to support RNA synthesis was assayed by the method of CHAMBERLIN and BERG (1962) with Escherichia coli RNA polymerase purified up to the step of fraction IV. The standard reaction mixture (0.25 ml) contained 10 micromoles of tris buffer, pH 7.9, 0.25 micromoles of MnCl2, 1.0 micromole of MgCl2, 100 micromoles each of CTP, GTP, and UTP, and 50 micromoles of 14C-ATP (specific activity: 8 microCi/microM). It was found that the isolated chromatin of wheat germinating embryos and aleurone layers can prim RNA synthesis in the presence of exogenous RNA polymerase. As shown in Table 1, the abilities of embryo chromatin and aleurone layer chromatin to support RNA synthesis are different. The template activity of embryo chromatin is about a half of the activity of wheat seedling DNA, and further the activity of aleurone layer chromatin is about a half of that of embryo chromatin. The results may suggest that more genes are available for transcription in embryo chromatin. However, endogenous RNA polymerase activity was very low in the chromatin prepared by the present method. Therefore, a comparison of real RNA synthesizing ability between the two chromatins has need of more precise investigation. Literature cited CHAMBERLIN, M. and BERG, P. 1962. Deoxyribonucleic acid-directed synthesis of ribonucleic acid by an enzyme from Escherichia coli. Proc. Nat. Acad. Sci. U, S. 48: 81-94. MARMUR, J. 1961. A procedure for the isolation of deoxyribonucleic acid from micro-organisms. J. Mol. Biol. 3: 208-218. SHIN, T. Y. and BONNER, J. 1969. Chromosomal RNA of calf thymus chromatin. Biochem. Biophys. Acta 182: 30-35. (Received April 18, 1971) |