Activation of ribosomal and messenger RNA synthesis in excised Jerusalem artichoke tuber slices.

RNA synthesis was studied in Jerusalem artichoke (Helianthus tuberosus L.) tuber slices immediately following excision and during the early period of aging in water. Incorporation of [(3)H]adenosine into RNA was detected as early as 20 min after excision. Measurement of the specific activities of RNA (cpm/μg) and of ATP showed that RNA synthesis proceeded at a constant rate for the first several hours of aging and then increased moderately. [(3)H]adenosine was incorporated into polysomes throughout the aging period examined. Sucrose gradient fractionation of EDTA-dissociated polysomes showed that during the first 2 h of aging most of this incorporation was not into ribosome subunits but into presumed mRNA. Autoradiographic analysis of [(3)H]adenosine labelled nuclei showed that this was caused, at least in part, by a delay in the onset of rRNA synthesis synthesized during this time chromatographed as poly(A)-RNA on oligo(dT)-cellulose, indicating that a large part of the mRNA was not polyadenylated.