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Articles

Transcription of Ribosomal and Messenger RNAs in Early Wheat Embryo Germination ¹

^a The Institute for Cancer Research, The Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111

Germinating wheat embryos (Triticum aestivum L). synthesize both ribosomal and messenger RNA at the earliest times after the onset of germination. The rates of synthesis of these two RNAs are determined at various stages in germination by an analysis of newly synthesized radioactive RNA on oligo(dT)-cellulose. The rate of messenger RNA synthesis is essentially constant throughout 18 hours of germination, while that of ribosomal RNA synthesis increases steadily, particularly after the onset of cell expansion (6 hours), reaching at 16 to 18 hours, a rate of synthesis between 5- and 20-fold greater than that observed at the earliest stages. The net effect is a relative decrease in the fraction of transcribed high molecular weight RNA that is mRNA. Throughout the first 7 hours of germination, mRNA is 25 to 30% of the transcribed fraction, whereas by 16 to 18 hours it has declined to a level of 4 to 8%.

¹ This work was supported by National Science Foundation Grant BG 35585X, by Grants CA-06927 and RR-05539 from the National Institutes of Health, United States Public Health Service, and by an appropriation from the Commonwealth of Pennsylvania.