Cucumber Cotyledon Lipoxygenase during Postgerminative Growth. Its Expression and Action on Lipid Bodies

• Published in: Plant physiology (Bethesda) Vol. 119; no. 4; pp. 1279 - 1287
• Main Authors: MATSUI, K, HIJIYA, K, TABUCHI, Y, KAJIWARA, T
• Format: Journal Article
• Language: English
• Published: Rockville, MD American Society of Plant Physiologists 01.04.1999; American Society of Plant Biologists; Oxford University Press
• Subjects: Agronomy. Soil science and plant productions; Amino Acid Sequence; Biological and medical sciences; Cotyledon - enzymology; Cotyledons; Cucumbers; Cucumis sativus; Cucumis sativus - enzymology; Cucumis sativus - genetics; Cucumis sativus - growth & development; Economic plant physiology; Enzymes; Fats; Fatty acids; Fundamental and applied biological sciences. Psychology; Gene Expression; Genes, Plant; Germination; Growth and Development; Lipid bodies; Lipid Metabolism; Lipids; Lipoxygenase - genetics; Lipoxygenase - isolation & purification; Lipoxygenase - metabolism; Messenger RNA; Molecular Sequence Data; Morphogenesis, differentiation, rhizogenesis, tuberization. Senescence; Organelles - metabolism; Oxidation-Reduction; Plant growth. Development of the storage organs; Plant physiology and development; Plant Proteins - isolation & purification; RNA, Messenger - genetics; RNA, Messenger - metabolism; RNA, Plant - genetics; RNA, Plant - metabolism; Seedlings; Solubility; Trypsin; Vegetative apparatus, growth and morphogenesis. Senescence; Cotyledon; Enzyme; Cucurbitaceae; Homology; Lipids; Cucumis sativus; Gene expression; Membrane enzyme; Vegetable crop; Enzymatic activity; Complementary DNA; Dicotyledones; Angiospermae; Turnover; Spermatophyta; Developmental stage; Oxidoreductases; Lipoxygenase; Localization; Aminoacid sequence
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.119.4.1279

In cucumber (Cucumis sativus), high lipoxygenase-1 (LOX-1) activity has been detected in the soluble fraction prepared from cotyledons of germinating seeds, and the involvement of this enzyme in lipid turnover has been suggested (K. Matsui, M. Irie, T. Kajiwara, A. Hatanaka [1992] Plant Sci 85: 23-32; I. Fuessner, C. Wasternack, H. Kindl, H. Kühn [1995] Proc Natl Acad Sci USA 92: 11849-11853). In this study we have investigated the expression of the gene lox-1, corresponding to the LOX-1 enzyme. LOX-1 expression is highly coordinated with that of a typical glyoxysomal enzyme, isocitrate lyase, during the postgerminative stage of cotyledon development. In contrast, although icl transcripts accumulated in tissue during in vitro senescence, no accumulation of lox-1 mRNA could be observed, suggesting that lox-1 plays a specialized role in fat mobilization. LOX-1 is also known to be a major lipid body protein. The partial peptide sequences of purified LOX-1 and lipid body LOX-1 entirely coincided with that deduced from the lox-1 cDNA sequence. The data strongly suggest that LOX-1 and lipid body LOX-1 are derived from a single gene and that LOX-1 can exist both in the cytosol and on the lipid bodies. We constructed an in vitro oxygenation system to address the mechanism of this dual localization and to investigate the action of LOX-1 on lipids in the lipid bodies. LOX-1 cannot act on the lipids in intact lipid bodies, although degradation of lipid body proteins, either during seedling growth or by treatment with trypsin, allows lipid bodies to become susceptible to LOX-1. We discuss the role of LOX-1 in fat mobilization and its mechanism of action.