On the Significance of Increased Protein Synthesis in Ripening Banana Fruits

Abstract

Banana fruit slices exposed to ethylene at a concentration of 5 µl per litre for 12 h ripened within 6 days. Slices treated with ethylene for only 6 h ripened at the same time as slices not treated with ethylene. Twenty four hours after the initiation of either a 6- or 12-h ethylene treatment, protein synthesis in pulp tissue showed similar increases. It is concluded that the increase in protein synthesis is a response to ethylene treatment rather than to ripening. Isotope dilution experiments show that radioactive valine added to pulp slices is diluted by endogenous valine before incorporation into protein. From the incorporation studies it is deduced that the ethylene-provoked increase in protein synthesis is responsible, within 24 h, for synthesis equivalent to a substantial proportion of the protein in pulp cells. Double-labelling experiments establish that the increased synthesis in response to ethylene treatment involves replacement of a large range of soluble proteins, and is not limited to the synthesis of a few specific proteins.