MONODEHYROASCORBATE REDUCTASE4 Is Required for Seed Storage Oil Hydrolysis and Postgerminative Growth in Arabidopsis

• Published in: The Plant cell 2007-04, Vol.19 (4), p.1376-1387
• Main Author: Eastmond, Peter J
• Format: Article
• Language: English
• Subjects: Arabidopsis - growth & development; Arabidopsis - ultrastructure; Arabidopsis Proteins - metabolism; Dehydrogenases; Enzymes; Fatty acids; Germination; Hydrogen peroxide; Hydrolysis; Lipid bodies; Lipids; Molecular Sequence Data; NADH, NADPH Oxidoreductases - metabolism; Organelles - enzymology; Organelles - ultrastructure; Oxidases; Peroxisomes; Phenotypes; Plant cells; Plant Oils - metabolism; Seedlings; Seeds - physiology; Sugar
• ISSN: 1040-4651; 1532-298X; 1532-298X
• DOI: 10.1105/tpc.106.043992

Hydrogen peroxide is a major by-product of peroxisomal metabolism and has the potential to cause critical oxidative damage. In all eukaryotes, catalase is thought to be instrumental in removing this H₂O₂. However, plants also contain a peroxisomal membrane-associated ascorbate-dependent electron transfer system, using ascorbate peroxidase and monodehydroascorbate reductase (MDAR). Here, I report that the conditional seedling-lethal sugar-dependent2 mutant of Arabidopsis thaliana is deficient in the peroxisomal membrane isoform of MDAR (MDAR4). Following germination, Arabidopsis seeds rely on storage oil breakdown to supply carbon skeletons and energy for early seedling growth, and massive amounts of H₂O₂ are generated within the peroxisome as a by-product of fatty acid β-oxidation. My data suggest that the membrane-bound MDAR4 component of the ascorbate-dependent electron transfer system is necessary to detoxify H₂O₂, which escapes the peroxisome. This function appears to be critical to protect oil bodies that are in close proximity to peroxisomes from incurring oxidative damage, which otherwise inactivates the triacylglycerol lipase SUGAR-DEPENDENT1 and cuts off the supply of carbon for seedling establishment.