Department of Biology, College of Life Science and Biotechnology, Yonsei University, Seoul 120-749, Korea.
J Exp Bot. 2011 Nov;62(15):5683-98. doi: 10.1093/jxb/err250. Epub 2011 Aug 18.
Lipid-derived molecules produced by acylhydrolases play important roles in the regulation of diverse cellular functions in plants. In Arabidopsis, the DAD1-like phospholipase A1 family consists of 12 members, all of which possess a lipase 3 domain. In this study, the biochemical and cellular functions of AtDLAH, an Arabidopsis thaliana DAD1-like acylhydrolase, were examined. Bacterially expressed AtDLAH contained phospholipase A1 activity for catalysing the hydrolysis of phospholipids at the sn-1 position. However, AtDLAH displayed an even stronger preference for 1-lysophosphatidylcholine, 1-monodiacylglycerol, and phosphatidic acid, suggesting that AtDLAH is a sn-1-specific acylhydrolase. The AtDLAH gene was highly expressed in young seedlings, and its encoded protein was exclusively localized to the mitochondria. AtDLAH-overexpressing transgenic seeds (35S:AtDLAH) were markedly tolerant to accelerated-ageing treatment and thus had higher germination percentages than wild-type seeds. In contrast, the atdlah loss-of-function knockout mutant seeds were hypersusceptible to accelerated-ageing conditions. The 35S:AtDLAH seeds, as opposed to the atdlah seeds, exhibited a dark red staining pattern following tetrazolium treatment under both normal and accelerated-ageing conditions, suggesting that AtDLAH expression is positively correlated with seed viability. The enhanced viability of 35S:AtDLAH seeds was accompanied by more densely populated epidermal cells, lower levels of accumulated lipid hydroperoxides, and higher levels of polar lipids as compared with wild-type and atdlah mutant seeds. These results suggest that AtDLAH, a mitochondrial-localized sn-1-specific acylhydrolase, plays an important role in Arabidopsis seed viability.
酰水解酶产生的脂质衍生分子在植物中多种细胞功能的调节中发挥重要作用。在拟南芥中，DAD1 样磷脂酶 A1 家族由 12 个成员组成，它们都具有脂肪酶 3 结构域。在这项研究中，研究了拟南芥 DAD1 样酰水解酶 AtDLAH 的生化和细胞功能。细菌表达的 AtDLAH 具有磷脂酶 A1 活性，可催化磷脂在 sn-1 位的水解。然而，AtDLAH 对 1-溶血磷脂酰胆碱、1-单酰甘油和磷脂酸表现出更强的偏好，表明 AtDLAH 是一种 sn-1 特异性酰水解酶。AtDLAH 基因在幼苗中高度表达，其编码的蛋白质仅定位于线粒体。AtDLAH 过表达转基因种子（35S:AtDLAH）对加速衰老处理明显耐受，因此发芽率高于野生型种子。相比之下，atdlah 功能丧失敲除突变体种子对加速衰老条件高度敏感。与野生型种子相比，35S:AtDLAH 种子在正常和加速衰老条件下经四唑处理后表现出明显的深红色染色模式，表明 AtDLAH 表达与种子活力呈正相关。与野生型和 atdlah 突变体种子相比，35S:AtDLAH 种子活力增强伴随着表皮细胞密度增加、积累的脂质氢过氧化物水平降低以及极性脂质水平升高。这些结果表明，定位于线粒体的 sn-1 特异性酰水解酶 AtDLAH 在拟南芥种子活力中发挥重要作用。
