EFFECT OF HIGH-TEMPERATURE ON PROTEIN-SYNTHESIS IN THE AXES OF IMBIBING PEA EMBRYOS

The effects of short (2-4 h) heat shock on in vive protein synthesis i n pea (Pisum sativum L.) embryo axes during early germination were stu died. During embryo imbibition, protein synthesis was resumed simultan eously at both optimum (28 degrees C) and elevated (40-42 degrees C) t emperatures. In both cases, alpha-amanitin (7 mu g/ml) inhibited early protein synthesis by 40-50%. Short heat shock markedly enhanced prote in synthesis during the first hours of imbibition; less pronounced sti mulation was observed at radicle emergence. Protein synthesis occurred at the highest rate at temperatures of 38-40 degrees C (depending on the cultivar), substantially higher than the optimum growth temperatur e (28 degrees C). Brief heating above 42 degrees C significantly depre ssed translation. Axes responded to short heat shock by the synthesis of a set of high-molecular-weight and low-molecular-weight heat shock proteins. During embryo imbibition up to radicle emergence, the synthe sis of heat shock proteins occurred concomitantly with the synthesis o f the bulk of ''normal'' proteins. Over the first hours of imbibition, numerous heat shock and normal proteins were synthesized in the prese nce of alpha-amanitin. The results obtained indicate that short heat s hock does not prevent the translation of most normal mRNAs and induces the synthesis of a complete set of heat shock proteins during the fir st hours of embryo axis imbibition. The active synthesis of both norma l and heat shock proteins in response to heat shock is thought to incr ease embryo thermotolerance and maintain seed capacity for germination .