Re-Activation of the Expression of Glyoxysomal Genes in Green Plant Tissue

Biochemie, Fachbereich Chemie, Universität Marburg, Hans-Meerwein-Straße, D-3550 Marburg, Bundesrepublik Deutschland Z. Naturforsch. 45c, Isocitrate Lyase c DNA, Malate Synthase c DNA, Glyoxysome, Leaf Peroxisome, Transition of Organelles Glyoxysomes are being replaced by leaf-type peroxisom es during the greening of dark-grown cucumber cotyledons. Light functions in this process as negative modulator of the gene expression of glyoxylate cycle enzymes but as positive regulator for the activation of glycollate oxidase formation. The differential gene expression was investigated at the level of m RNA amounts using c DNA probes hybridizing with malate synthase m RNA, isocitrate lyase m RNA, and glycollate oxidase m RNA. Hybrid ization probes were obtained from a c DNA library complementary to the germinationspecific m RNA s of cucumber cotyledons. The process of replacem ent of glyoxysomal proteins by leaf peroxisom al proteins was reversed to a certain extend when greened cotyledons were brought back in the dark. Hybridization on Northern b lots provided evidences that in greened cotyledons the amount of malate synthase m RNA and isocitratelyase m RNA starts to increase up on dark treatment.