Synthesis of rRNA, tRNA and other RNA-species concomitant with polyribosome formation in aging potato tuber slices.

One of the earliest consequences of slicing plant storage organs such as potato tubers into thin disks is the formation of polysomes, which in potato slices is complete after 9 hours and is dependent on transcription. Fresh disks do not incorporate 32P, 3H-uridine or 14C-leucine into their ribosomes, whereas ribosomes and polysomes of aged disks use these precursors effectively. This development can be completely blocked by actinomycin D. Among the different RNAs synthesized during aging is 28Sand 16S — rRNA, 5S —RNA, tRNA, and a component sedimenting around 15 —18S with a base-composition different from 16S — rRNA, 5Sand 4S — RNA and which supports peptide formation in an in vitro incorporation system. It is suggested that this compound represents mRNA, which is not available immediately after slicing the tissue. These findings are consistent with the view of a derepression phenomenon in sliced storage tissue.