Plant microbodies and their enzymes represent an attractive system for studies of the synthesis and compartmentalization of organellar proteins. Dr. Becker intends to continue our investigation of the appearance and import of both glyoxysomal and peroxisomal enzymes in the cotyledons of cucumber (Cucumis sativus) seedlings during early postgerminative development. At the molecular level, Dr. Becker has already shown, by in vitro translation, that regulation of enzyme accumulation is primarily at a pretranslational level. He has now isolated cDNA clones for two glyoxysomal enzymes and two peroxisomal enzymes. These clones will be used as probes to assay for transcript appearance during post germinative development and greening of cotyledons. He also intends to isolate and sequence genomic clones and to characterize their regulatory sequences. If time permits, he plans to begin a functional analysis of gene regulation using Arabidopsis thaliana, for which conditionally-lethal photorespiratory mutants are available. At the subcellular level, he intends to study the mechanism whereby microbody proteins are targeted to and imported into the organelle, using both in vitro and in vivo approaches. %%% Many cellular metabolic pathways require enzymes that are encoded by the nuclear genome and synthesized on cytoplasmic ribosomes, yet are active only within specific membrane-bound compartments. The appearance of such metabolic pathways during development therefore involves both expression of the appropriate genetic information and the compartmentalization of the gene products. Dr. Becker is studying the development of the enzymes involved in photorespiration. The enzymes responsible for these pathways all come to be localized in a membrane bound organelles and Dr. Becker plans to use molecular genetic techniques to determine how these enzymes are transported across the membrane into the subcellular organelles where they function.
