Regulation of nitrate reductase synthesis during early germination in seeds of barley (Hordeum vulgare)

Abstract

During seed germination in barley, a non - inducible phase of 24 - 26 h was found to exist for the induction of nitrate reductase (NR) in both light and dark. The non - inducible phase for NR was not due to the non - availability of nitrate ions or the presence of an enzyme inactivating factor or the synthesis of an inactive NR. At the initiation of the inducible phase, the enzyme was synthesized de novo but did not require synthesis of fresh mRNA. This was evident from the studies with inhibitors of RNA and protein synthesis. The metabolic activity during the non -inducible phase, probably synthesis of a protein, was essential to make the embryos sensitive to NR induction in the inducible phase. Actinomyc in- D, superinduced the enzyme. By examining various possibilities a post - transcriptional control for the superinduction has been suggested.