Biogenesis of Peroxisomes in Plants

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Three different aspects of plant peroxisome biogenesis will be pursued: (1), the means by which the expanding membrane of oilseed glyoxysomes acquires its protein and lipid is an integral part of the organelle biogenesis. The hypothesis will be tested that lipid bodies contribute membrane lipid to differentiating oilseed glyoxysomes; (2), parameters and conditions necessary and/or sufficient for recognition and tranlocation in vivo of malate synthase, isocitrate lyase and catalase into peroxisomes of cultured monkey kidney and selected plant cells will be determined; (3) studies will continue on deciphering patterns of regulation and developmental expression of catalase isoforms during the changeover from glyoxysomes to leaf-type peroxisomes, and of isocitrate lyase and malate synthase during glyoxysome differentiation in maturing and germinated seeds. The availability of an embryo culture system is expected to provide a unique means to help resolve regulation patterns within maturing seeds. Peroxisomes occur in virtually all eukaryotic cells, conducting a variety of essential metabolic functions depending on the cell type in which they reside. They are not capable of synthesizing their own phospholipids or proteins, and are therefore dependent upon the selective and complicated intracellular trafficking mechanisms responsible for their biogenesis. The objectives of this proposal are to examine the molecular and biochemical bases of selected, interrelated aspects of peroxisome biogenesis; the emphasis will be on cottonseed glyoxysomes.