Mitochondrial GPAT-derived LPA controls auxin-dependent embryonic and postembryonic development

背景回顾：Membrane properties are emerging as important cues for the spatiotemporal regulation of hormone signaling. Lysophosphatidic acid (LPA) evokes multiple biological responses by activating G protein–coupled receptors in mammals. 

主要发现：In this study, we demonstrated that LPA derived from the mitochondrial glycerol-3-phosphate acyltransferases GPAT1 and GPAT2 is a critical lipid-based cue for auxin-controlled embryogenesis and plant growth in Arabidopsis thaliana. 

结果1-GPAT1/2-LPA-PIN1：LPA levels decreased, and the polarity of the auxin efflux carrier PIN-FORMED1 (PIN1) at the plasma membrane (PM) was defective in the gpat1 gpat2 mutant. As a consequence of distribution defects, instructive auxin gradients and embryonic and postembryonic development are severely compromised. 

结果2-LPA-PIN1-auxin：Further cellular and genetic analyses revealed that LPA binds directly to PIN1, facilitating the vesicular trafficking of PIN1 and polar auxin transport. 

结论：Our data support a model in which LPA provides a lipid landmark that specifies membrane identity and cell polarity, revealing an unrecognized aspect of phospholipid patterns connecting hormone signaling with development.

Schematic illustration of the interaction between LPA and PIN1 in the regulation of auxin signaling.

越来越多的研究表明，细胞膜的特性作为激素信号时空调节的重要线索发挥功能。在哺乳动物中，溶血磷脂酸（LPA）通过激活G蛋白偶联受体介导多种生物响应。本文中，作者发现源自线粒体的甘油-3-磷酸酰基转移酶GPAT1和GPAT2的LPA是拟南芥中生长素控制的胚胎发生和植物生长的关键脂质线索。在gpat1 gpat2双突变体中，LPA水平降低，并且质膜（PM）上生长素外流载体PIN-FORMED1（PIN1）的极性存在缺陷。由于PIN1的分布缺陷，向性的长素梯度以及胚胎发育和胚后发育受到严重影响。进一步的细胞和遗传分析表明，LPA可直接与PIN1结合，促进PIN1的囊泡运输和极性生长素运输。本文的研究结果表明LPA提供了一个脂质标志物，能够制定细胞膜的特性和细胞极性，揭示了一个作用于连接激素信号和植物生长发育的未知磷脂模式。

** 张 群 **