SUGAR-DEPENDENT1 Encodes a Patatin Domain Triacylglycerol Lipase That Initiates Storage Oil Breakdown in Germinating Arabidopsis Seeds

• Published in: The Plant cell 2006-03, Vol.18 (3), p.665-675
• Main Author: Eastmond, Peter J
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; amino acid sequences; Amino acids; Arabidopsis - embryology; Arabidopsis - enzymology; Arabidopsis - genetics; Arabidopsis thaliana; Carboxylic Ester Hydrolases - chemistry; Carboxylic Ester Hydrolases - genetics; Carboxylic Ester Hydrolases - physiology; cell membranes; Chromosome Mapping; Cloning; Cloning, Molecular; diacylglycerols; enzymatic hydrolysis; enzyme activity; Enzymes; Esters; Fatty acids; gene expression; Germination; Germination - physiology; Hydrolysis; Intracellular Membranes - metabolism; Lipase - chemistry; Lipase - genetics; Lipase - physiology; Lipid bodies; Lipids; Lipolysis; messenger RNA; Molecular Sequence Data; mutants; nucleotide sequences; oil body membranes; organelles; patatin; phenotype; Phylogeny; Plant cells; Plant Oils - metabolism; Protein Structure, Tertiary; Recombinant Fusion Proteins - analysis; seed germination; seed oils; Seedlings; Seedlings - genetics; Seedlings - growth & development; Seedlings - ultrastructure; Seeds; Seeds - enzymology; Seeds - genetics; Seeds - growth & development; Sequence Alignment; Substrate Specificity; Sugar; triacylglycerol lipase; triacylglycerols; Triglycerides; Triglycerides - metabolism; Yeasts
• ISSN: 1040-4651; 1532-298X; 1532-298X
• DOI: 10.1105/tpc.105.040543

Triacylglycerol hydrolysis (lipolysis) plays a pivotal role in the life cycle of many plants by providing the carbon skeletons and energy that drive postgerminative growth. Despite the physiological importance of this process, the molecular mechanism is unknown. Here, a genetic screen has been used to identify Arabidopsis thaliana mutants that exhibit a postgerminative growth arrest phenotype, which can be rescued by providing sugar. Seventeen sugar-dependent (sdp) mutants were isolated, and six represent new loci. Triacylglycerol hydrolase assays showed that sdp1, sdp2, and sdp3 seedlings are deficient specifically in the lipase activity that is associated with purified oil bodies. Map-based cloning of SDP1 revealed that it encodes a protein with a patatin-like acyl-hydrolase domain. SDP1 shares this domain with yeast triacylglycerol lipase 3 and human adipose triglyceride lipase. In vitro assays confirmed that recombinant SDP1 hydrolyzes triacylglycerols and diacylglycerols but not monoacylglycerols, phospholipids, galactolipids, or cholesterol esters. SDP1 is expressed predominantly in developing seeds, and a SDP1-green fluorescent protein fusion was shown to associate with the oil body surface in vivo. These data shed light on the mechanism of lipolysis in plants and establish that a central component is evolutionarily conserved among eukaryotes.