CHANGES IN PROTEIN-COMPOSITION DURING STRAWBERRY (FRAGARIA X ANANASSA-DUCH) FRUIT RIPENING

The changes in strawberry native proteins and polypeptides during ripe ning were studied. Analysis of protein extracts by nondenaturing elect rophoresis showed the presence of a protein species only in the '25% R ed' and later ripening stage. This 40 kD polypeptide was hardly detect ed in 'Large green' and 'White' fruit extracts. The polypeptide profil e, obtained with SDS-PAGE, also changed during ripening. While most po lypeptides were found in all ripening stages, the distribution of some of them varied during ripening. Protein synthesis (measured by S-35-m ethionine labelling) in strawberry was mainly directed towards the reg eneration of previously existing proteins. As ripening proceeded, the synthesis of 67 and 63 kD polypeptides increased, while those of 82, 5 6 and 25 kD decreased. Three very-abundant polypeptides (36, 24 and 23 kD) were located in the achenes and were not labelled in any ripening stage.