The formation and translational activity of polysomes from developing lupin seeds

Abstract

The formation and in vitro translational activity of total, free and membrane‐bound polysomes from various stages of developing cotyledons of yellow lupin seeds (Lupinus luteus L. cv. Iryd) has been investigated. The early stages of seed formation were characterized by a low level of polysomes that progressively increased. The main features of the cotyledons at the middle phase of development were full expansion growth and the highest amount of polysomes observed in all three poly so me fractions. In The final stages of emhryogenesis. the seed dehydration was accompanied by‐gradual loss of all types of polysomes, at which the membrane‐attached formations were degraded earlier than the free ones. By means of a wheat germ‐derived cell‐free system for protein synthesis, a correlation was demonstrated between cotyledon growth, polysome formation and their capacity for protein synthesis in vitro. As compared to the free polysomes, both the total and membrane‐bound formations were more active in protein synthesis in vitro. Analysis of the translational products by means of immunoprecipitation and gel electrophoresis followed by fluorography showed that only membrane‐bound polysomes produced polypeptides of higher molecular weight, including subunits of a legumin‐like protein.