Regulation of Peroxidase Activity by Ethylene inPisum sativum: Requirements for Protein and RNA Synthesis

Abstract

When exposed to ethylene at concentrations of 1 ppm or more etiolated seedlings of Pisum sativum var. Alaska show increased levels of peroxidase activity in all parts of the plant. The mechanisms controlling this increase have been studied in excised segments from the epicotyl. Such segments show a natural rise in peroxidase activity when incubated in buffered medium and this rise is enhanced by ethylene. By the use of inhibitors it was found that continuous protein synthesis is necessary for enhanced peroxidase activity and for the stimulating effect of ethylene. Synthesis of RNA is also required but only during the early period of incubation. Evidence is presented that young apical tissue, but not mature basal tissue, contains an endogenous inhibitor of peroxidase synthesis. However, ethylene does not appear to enhance peroxidase activity through effects on this inhibitor. The results suggest that ethylene regulates the activity of peroxidase at a translational rather than a transcriptional level.