Wounding of Aged Pea Epicotyls Enhances the Reinitiating Ability of Isolated Ribosomes

Total ribosomes (monosomes plus polysomes) isolated from woundedpea epicotyls are more efficient at supporting protein synthesisin a wheat germ S₃₀ system (containing wheat ribosomes) thanare total ribosomes from aged (control) pea tissue. This increasedefficiency is seen when enriched large polysomes, almost devoidof monosomes, are used to program a wheat germ S₃₀₀ system,from which the wheat germ ribosomes have been removed. Reactionsprimed by enriched polysomes from wounded tissue, but not agedtissue, continue for at least 30 min, suggesting that reinitiationis occurring during the reaction, albeit in the initial absenceof monosomes from wheat or pea. Wheat germ ribosomes, but notmonosomes from either aged or wounded pea tissue, are able totranslate pea poly(A) RNA and globin mRNA. Aurintricarboxylicacid reduces protein synthesis in a rather indiscriminate manner,whereas, pactamycin seems to have an inhibitory effect specificfor initiation, and it is much more effective on wounded thanon control tissue polysomes. We interpret these results to implythat polysomal ribosomes from wounded tissue are more efficientat initiation than are polysomal ribosomes from control tissueor than non-polysomal ribosomes (monosomes) from either tissue. (Received May 7, 1985; Accepted July 4, 1985)