REGULATION OF GLYOXYSOMAL ENZYMES DURING GERMINATION OF CUCUMBER - TEMPORAL CHANGES IN TRANSLATABLE MESSENGER-RNAS FOR ISOCITRATE LYASE AND MALATE SYNTHASE

Abstract

The relative levels of translatable mRNA for isocitrate lyase and malate synthase were determined in the dry seed, and for the first 7 days of development of cucumber cotyledons. After extraction and quantification of total and poly(A)-rich RNA each day, the RNA fractions were translated in an optimized wheat germ system, and the specific polypeptides were immunoprecipitated quantitatively. The radiolabeled isocitrate lyase and malate synthase polypeptides were fractionated on dodecylsulphage/polyacrylamide gels, visualized by exposure to X-ray film, and quantified densitometrically. The relative levels of translatable mRNA for these enzymes rise and fall with a developmental program similar to the enzyme activities, but preceding the latter by .apprx. 1 day. The rise in enzyme activity apparently is dependent upon a prior postgerminative increase in translatable mRNA for the enzymes. mRNA levels may be regulated, at least in part, by light.