EFFECT OF LIGHT ON THE ACTIVITY OF THE PROTEIN SYNTHESIZING SYSTEM IN WHEAT SEEDLING

Light, an important regulatory factor in the growth and development of plant, influences not only the quantity and composition of the RNAs, but also the modified nucleotide composition of the tRNAs and rRNAs, since under-modified RNAs are formed due to the lack of light, gradually returning to the modification level characteristic of the RNAs in green plants in the course of illumination. The current experiments were aimed at investigating how tRNAs obtained from etiolated plants, or from plants greened for various lengths of time, influenced the activity of cell-free protein synthesising systems, and what changes in activity were brought about by changes occurring in other components of the protein synthesising system due to the effect of greening. It was found that under-modified tRNAs caused a substantial reduction in the intensity of protein synthesis, i.e. in the incorporation into the proteins of the labelled amino acids, and the activity characteristic of green plants could only be restored with tRNA obtained from plant greened for 48 h. At the same time, changes induced by etiolation in other components of the protein synthesising system (e.g. rRNA under-modification) reduced the intensity of protein synthesis to a lesser extent.