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

Abstract

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.

Characterization of a cDNA Encoding Lens culinaris Glycolate Oxidase and Developmental Expression of Glycolate Oxidase mRNA in Cotyledons and Leaves

“…Lentil glycolate oxidase has a similar motif as cucumber hydroxypyruvate reductase (13) and soybean urate oxidase (22). Similarities with cucumber catalase (H Kindl, unpublished data), cucumber malate synthase (5,26), Brassica napus (7) malate synthase, and cucumber (2) isocitrate lyase are discernible.…”

Functional analysis and regulation of the malate synthase from Chlamydomonas reinhardtii

“…Oilseed plants regulate the glyoxylate cycle by its specific induction during seed development, and by turning it off once green tissues can achieve photoautotrophic growth (Ettinger and Harada 1990;Birkhan and Kindl 1990). In contrast, less restrictive living conditions of many microorganisms might have forced the preservation of more versatile metabolisms, such as the use of the glyoxylate cycle to assimilate exogenous twocarbon compounds.…”

“…The other cycle regulator is light. In fact, in oilseed plants it functions as a negative regulator when photoautotrophic growth is established (Allen et al 1988;Ettinger and Harada 1990;Birkhan and Kindl 1990). It has not yet been determined whether the negative regulation by light is mediated by the metabolites produced from a light reaction or directly by light itself through a photoreceptor.…”

The leaf peroxisomal form (MFP IV) of multifunctional protein functioning in fatty-acid ?-oxidation

“…As large amounts of endogenous fat are not present in green leaves the role of glyoxysomes in this tissue is almost totally switched off. Glyoxysomal function only resumes when leaves become senescent (Gut and Matile 1988;Birkhan and Kindl 1990;De Bellis and Nishimura 1991).…”