Adaptive Potential of Wheat Ribosomes toward Heat Depends on the Large Ribosomal Subunit and Ribosomal Protein Phosphorylation.
In a study of the translational efficiency of ribosomal subunits as a function of an in vivo temperature pretreatment, ribosomes were isolated from heat-pretreated (36 degrees C) and reference (20 degrees C) wheat seedlings (Triticum aestivum L.). The efficiency of recombined subunits in translating polyuridylic acid was assessed. A threefold increase in the rate of incorporation of phenylalanine by ribosomes from heat-pretreated plants was due to the large ribosomal subunit. This adaptive temperature effect was not correlated with a higher thermal stability of ribosomes or subunits from heat-pretreated seedlings, and two-dimensional gel electrophoresis failed to detect structural alterations of ribosomal proteins. Phosphorylation of ribosomal proteins in vitro showed no differences between ribosomes or subunits from heat-pretreated and reference plants. Incubation with [(32)P]orthophosphate in vivo led to twice the amount of phosphate in ribosomal proteins from heat-pretreated wheat seedlings. This result is important with respect to the evaluation of the molecular basis of enhanced translational efficiency of ribosomes isolated from heat-pretreated wheat seedlings.
Fehling
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Botanisches Institut, III, Lehrstuhl, Universität zu Köln, Gyrhofstrasse 15, D-5000 Köln 41, Federal Republic of Germany.
Weidner
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