Distinctive characteristics of RNA and protein synthesis in pea cotyledons at early stages of germination

Abstract

The RNA and protein synthesis in pea cotyledons at early imbibition were studied. The results obtained show that RNA and protein synthesis are reactivated at the beginning of imbibition. The initial transcription is independent of protein synthesis, after 8 h synthesis RNA depends on translation by 44 – 52%. α-Amanitin (5μg ml−1) inhibits3H-uridine incorporation by 75%. It indicates the predominance of mRNA synthesis in early transcription. The protein synthesis during first hours of imbibition depends significantly (by 50%) on RNA synthesis. It means newly-made mRNA is involved in the translation. Protein synthesis, which is independent of transcription, is provided by preformed mRNA. This fraction of translation decreases rapidly during imbibition. Thus, protein synthesis in pea cotyledons depends mainly on newly-synthesized mRNA. Thein vivo synthesized polypeptides were fractionated by SDS-gel electrophoresis and visualized by autoradiography. The pattern of protein synthesis after 4 h of imbibition is very complex. Newly-synthesized polypeptides vary in m.m. (from 10 000 to 100 000), subcellular localization and solubility.14C-labelled polypeptides do not belong to subunits of storage proteins. The patterns of proteins, synthesized at different germination time (from 2 to 24 h), have much in common, but definite quantitative and qualitative changes in messenger population can be observed. During maturation of seed, the pattern of protein synthesis in pea cotyledons is changed rather quantitatively than qualitatively. Drastic changes in population of mRNA are observed in late embryogenesis. Patterns of proteins synthesized in late embryogenesis and early germination are similar.