Uncoupling of the Formation of Polysomes from Transcription at the Early Stage of Wound Response in Potato Tuber Slices

The level of polysomes in potato tuber slices increased immediately after slicing and reached approximately 2.5 times the level in fresh tissue within the first hour of aerobic incubation (aging). While treatment with actinomycin D or a-amanitin inhibited the synthesis of polysomal mRNA by more than 80%, formation of polysomes during the first hour of aging was not inhibited by these inhibitors. Analysis of the products of translation in vitro from polysomal RNA by two-dimensional polyacrylamide gel electrophoresis showed that the composition of translatable mRNAs associated with polysomes changed markedly within 1 h of aging, but most of these changes were suppressed by actinomycin D. These results indicate that transcription is rapidly activated by wounding and that newly synthesized mRNA is integrated into polysomes as early as 1 h after slicing. Furthermore, wound-induced increments in levels of polysomes are not always coupled to wound-induced transcription. A considerable number of mRNAs and/or their precursors are present in fresh tissue but are not associated with polysomes. Wound injury stimulates the translational activity of ribosomes, leading to rapid formation of polysomes on pre-existing mRNAs, when transcription is inhibited by actinomycin D.