Section Plant Physiology, Swammerdam Institute for Life Sciences, University of Amsterdam, Science Park 904, Amsterdam, XH, The Netherlands.
Section Plant Cell Biology, Swammerdam Institute for Life Sciences, University of Amsterdam, Science Park 904, Amsterdam, XH, The Netherlands.
Plant Cell Physiol. 2018 Oct 1;59(10):2004-2019. doi: 10.1093/pcp/pcy120.
Phospholipase C (PLC) is a well-known signaling enzyme in metazoans that hydrolyzes phosphatidylinositol 4,5-bisphosphate (PIP2) to produce inositol 1,4,5-trisphosphate and diacylglycerol as second messengers involved in mutiple processes. Plants contain PLC too, but relatively little is known about its function there. The model system Arabidopsis thaliana contains nine PLC genes. Reversed genetics have implicated several roles for PLCs in plant development and stress signaling. Here, PLC5 is functionally addressed. Promoter-β-glucuronidase (GUS) analyses revealed expression in roots, leaves and flowers, predominantly in vascular tissue, most probably phloem companion cells, but also in guard cells, trichomes and root apical meristem. Only one plc5-1 knock-down mutant was obtained, which developed normally but grew more slowly and exhibited reduced primary root growth and decreased lateral root numbers. These phenotypes could be complemented by expressing the wild-type gene behind its own promoter. Overexpression of PLC5 (PLC5-OE) using the UBQ10 promoter resulted in reduced primary and secondary root growth, stunted root hairs, decreased stomatal aperture and improved drought tolerance. PLC5-OE lines exhibited strongly reduced phosphatidylinositol 4-monophosphate (PIP) and PIP2 levels and increased amounts of phosphatidic acid, indicating enhanced PLC activity in vivo. Reduced PIP2 levels and stunted root hair growth of PLC5-OE seedlings could be recovered by inducible overexpression of a root hair-specific PIP 5-kinase, PIP5K3. Our results show that PLC5 is involved in primary and secondary root growth and that its overexpression improves drought tolerance. Independently, we provide new evidence that PIP2 is essential for the polar tip growth of root hairs.
磷酸脂酶 C（PLC）是后生动物中一种众所周知的信号酶，它可以水解磷脂酰肌醇 4,5-二磷酸（PIP2），生成肌醇 1,4,5-三磷酸和二酰基甘油，作为参与多种过程的第二信使。植物也含有 PLC，但对其功能的了解相对较少。模式植物拟南芥含有 9 个 PLC 基因。反向遗传学研究表明 PLC 在植物发育和应激信号转导中具有多种作用。在这里，我们对 PLC5 进行了功能分析。启动子-β-葡萄糖醛酸酶（GUS）分析显示，其在根、叶和花中表达，主要在维管束组织中，很可能是韧皮部伴胞，但也在保卫细胞、毛状体和根尖分生组织中表达。只获得了一个 plc5-1 敲低突变体，该突变体发育正常，但生长速度较慢，表现出主根生长减少和侧根数量减少。这些表型可以通过在其自身启动子的控制下表达野生型基因来互补。使用 UBQ10 启动子过表达 PLC5（PLC5-OE）导致初级和次级根生长减少、根毛发育不良、气孔孔径减小和耐旱性提高。PLC5-OE 系表现出显著降低的磷脂酰肌醇 4-单磷酸（PIP）和 PIP2 水平和增加的磷脂酸水平，表明体内 PLC 活性增强。PLC5-OE 幼苗中 PIP2 水平降低和根毛生长不良可以通过诱导过表达根毛特异性 PIP5-激酶 PIP5K3 来恢复。我们的结果表明 PLC5 参与初级和次级根生长，其过表达可提高耐旱性。独立地，我们提供了新的证据表明 PIP2 是根毛极性顶端生长所必需的。
