Concomitant induction of phenylalanine ammonia-lyase and flavanone synthase mRNAs in irradiated plant cells.

J Schröder,F Kreuzaler,E Schäfer,K Hahlbrock

doi:10.1016/s0021-9258(17)30271-5

Abstract

Irradiation of previously dark-grown cell suspension cultures from parsley (Petroselinum hortense Hoffm.) with ultraviolet light caused large, concomitant increases in mRNA activities for two characteristic enzymes of phenylpropanoid metabolism, phenylalanine ammonia-lyase, and flavanone synthase. The rates of enzyme synthesis both in vitro in a reticulocyte lysate and in vivo were quantitated by direct immunoprecipitation of the labeled enzyme subunits. Following a period of about 2 h, during which possible changes were below the limits of detectability, the two mRNA activities increased rapidly in irradiated cells for serveral hours. Phenylalanine ammonia-lyase mRNA reached a peak in activity a few hours earlier than flavanone synthase mRNA. The apparent half-lives of the enzyme activities were about 7 to 10 h for phenylalanine ammonia-lyase and 5 to 7 h for flavanone synthase. These data were used to calculate the expected, light-induced changes in enzyme activity from the measured changes in mRNA activity. The results for both enzymes were in agreement with experimental data, indicating that the light-induced changes in enzyme activity can be explained by changes in the respective mRNA activity. Some data concerning changes in the degree of polyadenylation of the mRNAs and the inhibitory effects of 7-methylguanosine 5'-phosphate are presented.

Highlights

With ultraviolet light caused large, concomitant increases in mRNA activities for two characteristic enzymes of phenylpropanoid metabolism, phenylalanine ammonia-lyase, and flavanone synthase
A similar co-migration of the proteins synthesized in uiuo and in vitro, and their correspondence in molecular weight to the native enzyme subunits have been demonstrated for phenylalanine ammonia-lyase (5)
The results presented here indicate a remarkable degree of similarity between the curves obtained for light-induced changes in phenylalanine ammonia-lyase and flavanone synthase mRNA activities

Summary

Introduction

With ultraviolet light caused large, concomitant increases in mRNA activities for two characteristic enzymes of phenylpropanoid metabolism, phenylalanine ammonia-lyase, and flavanone synthase. The apparent half-lives of the enzyme activities were about 7 to 10 h for phenylalanine ammonia-lyase and 5 to 7 h for flavanone synthase These data were used to calculate the expected, light-induced changes in enzyme activity from the measured changes in mRNA activity. We compare the light-induced changes in mRNA activities for phenylalanine ammonia-lyase and flavanone synthase. A further useful approach was to compare experimentally derived data for changes in enzyme activity with data obtained by mathematical calculations from changes in the rate of enzyme synthesis, as performed in a previous study of light-induced changes in phenylalanine ammonia-lyase synthesis in uiuo (10). In view of reports on the relationship between mRNA stability and the degrees of 3’-terminal polyadenylation (11) and 5’-

Methods

Results

Conclusion