NATURAL INHIBITORS OF GERMINATION AND GROWTH, VII-SYNTHESIS OF RIBULOSEBISPHOSPHATE CARBOXYLASE IN DARKNESS AND ITS INHIBITION BY COUMARIN

Cress (Lepidium sativum) seeds were germinated in darkness. Seedlings were investigated for soluble proteins by SDS-PAGE. Two proteins were identified by microsequencing: the small subunit of ribulosebisphospha te carboxylase (SSU) and the alpha subunit of the storage protein cruc iferin. Net synthesis of small and large subunits of ribulosebisphosph ate carboxylase (SSU and LSU) was investigated by Western blot. Net sy nthesis of both subunits was inhibited by coumarin. To the contrary, n et synthesis of cruciferin was increased by coumarin. With specific cD NA probes, we determined steady state levels of the corresponding mRNA s (rbcS mRNA for SSU, rbcL mRNA for LSU). Both mRNAs can be detected i n dry seeds; their amount increases during germination in the dark. In cubation with coumarin inhibits this increase. Inhibition of developme nt by coumarin on the level of transcription is discussed.