Eastmond Peter J
Department of Biology, Centre for Novel Agricultural Products, University of York, York YO10 5YW, United Kingdom.
Plant Cell. 2006 Mar;18(3):665-75. doi: 10.1105/tpc.105.040543. Epub 2006 Feb 10.
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.
三酰甘油水解（脂解作用）在许多植物的生命周期中起着关键作用，它能提供驱动种子萌发后生长的碳骨架和能量。尽管这一过程具有重要的生理学意义，但其分子机制尚不清楚。在此，通过遗传筛选鉴定出了拟南芥突变体，这些突变体表现出种子萌发后生长停滞的表型，而提供糖类可以挽救这种表型。分离出了17个糖依赖型（sdp）突变体，其中6个代表新的基因座。三酰甘油水解酶分析表明，sdp1、sdp2和sdp3幼苗在与纯化油体相关的脂肪酶活性方面存在特异性缺陷。基于图谱的SDP1克隆显示，它编码一种具有类马铃薯Patatin酰基水解酶结构域的蛋白质。SDP1与酵母三酰甘油脂肪酶3和人类脂肪甘油三酯脂肪酶共享该结构域。体外分析证实，重组SDP1能水解三酰甘油和二酰甘油，但不能水解单酰甘油、磷脂、半乳糖脂或胆固醇酯。SDP1主要在发育中的种子中表达，并且SDP1-绿色荧光蛋白融合体在体内显示与油体表面相关。这些数据揭示了植物脂解作用的机制，并确定了一个核心成分在真核生物中是进化保守的。
