Arabidopsis lipins mediate eukaryotic pathway of lipid metabolism and cope critically with phosphate starvation
Arabidopsis lipins mediate eukaryotic pathway of lipid metabolism and cope critically with phosphate starvation
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DOI：
10.1073/pnas.0907173106
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发表时间：
2009-12-08
影响因子：
11.1
通讯作者：
Ohta, Hiroyuki
中科院分区：
文献类型：
--
作者：
Nakamura, Yuki;Koizumi, Ryota;Ohta, Hiroyuki
磷酸盐是植物生存所必需的营养物质。众所周知，磷酸盐饥饿会触发膜脂重塑，这是一个将相当大一部分磷脂转化为不含磷的半乳糖脂的过程。这种重构是由磷脂酶C(PLC)或磷脂酶D(PLD)与磷脂酸磷酸酶(PAP)共同介导的。两个PLC基因NPC4和NPC5以及PLD基因PLD Zeta 1和PLD Zeta 2被证明参与了重塑。然而，基因敲除研究表明，它们中没有一个在重塑中起决定性作用。因此，虽然这种现象在植物中被广泛观察到，但负责整个植物体内脂质重塑的关键酶(S)尚不清楚，因此，这一转换过程的生理意义仍有待阐明。在这里，我们重点研究了PAP作为这种适应的关键酶，并鉴定了拟南芥脂类同源物AtPAH1和AtPAH2，它们编码参与半乳脂生物合成的PAP。双突变体pah1pah2降低了磷脂酸的水解率，从而影响了真核细胞合成半乳脂的途径。在磷饥饿条件下，pah1pah2植株的生长和膜脂重塑严重受损。这些结果表明，PAH1和PAH2是真核生物半乳脂合成途径中的PAP，这两种酶介导的膜脂重塑是应对磷酸盐饥饿的重要适应机制。
Phosphate is an essential nutrient for plant viability. It is well-established that phosphate starvation triggers membrane lipid remodeling, a process that converts significant portion of phospholipids to non-phosphorus-containing galactolipids. This remodeling is mediated by either phospholipase C (PLC) or phospholipase D (PLD) in combination with phosphatidate phosphatase (PAP). Two PLC genes, NPC4 and NPC5, and PLD genes, PLD zeta 1 and PLD zeta 2, are shown to be involved in the remodeling. However, gene knockout studies show that none of them plays decisive roles in the remodeling. Thus, although this phenomenon is widely observed among plants, the key enzyme(s) responsible for the lipid remodeling in a whole plant body is unknown; therefore, the physiological significance of this conversion process has remained to be elucidated. We herein focused on PAP as a key enzyme for this adaptation, and identified Arabidopsis lipin homologs, AtPAH1 and AtPAH2, that encode the PAPs involved in galactolipid biosynthesis. Double mutant pah1pah2 plants had decreased phosphatidic acid hydrolysis, thus affecting the eukaryotic pathway of galactolipid synthesis. Upon phosphate starvation, pah1pah2 plants were severely impaired in growth and membrane lipid remodeling. These results indicate that PAH1 and PAH2 are the PAP responsible for the eukaryotic pathway of galactolipid synthesis, and the membrane lipid remodeling mediated by these two enzymes is an essential adaptation mechanism to cope with phosphate starvation.