Leibniz University of Hannover, Institute of Floriculture and Wood Science, Section of Applied Molecular Physiology, Herrenhäuser Strasse 2, D-30419 Hannover, Germany.
Mol Plant. 2010 May;3(3):610-25. doi: 10.1093/mp/ssq005.
Phosphatidylcholine-hydrolyzing phospholipase C (PC-PLC) catalyzes the hydrolysis of phosphatidylcholine (PC) to generate phosphocholine and diacylglycerol (DAG). PC-PLC has a long tradition in animal signal transduction to generate DAG as a second messenger besides the classical phosphatidylinositol splitting phospholipase C (PI-PLC). Based on amino acid sequence similarity to bacterial PC-PLC, six putative PC-PLC genes (NPC1 to NPC6) were identified in the Arabidopsis genome. RT-PCR analysis revealed overlapping expression pattern of NPC genes in root, stem, leaf, flower, and silique. In auxin-treated P(NPC3):GUS and P(NPC4):GUS seedlings, strong increase of GUS activity was visible in roots, leaves, and shoots and, to a weaker extent, in brassinolide-treated (BL) seedlings. P(NPC4):GUS seedlings also responded to cytokinin with increased GUS activity in young leaves. Compared to wild-type, T-DNA insertional knockouts npc3 and npc4 showed shorter primary roots and lower lateral root density at low BL concentrations but increased lateral root densities in response to exogenous 0.05-1.0 μM BL. BL-induced expression of TCH4 and LRX2, which are involved in cell expansion, was impaired but not impaired in repression of CPD, a BL biosynthesis gene, in BL-treated npc3 and npc4. These observations suggest NPC3 and NPC4 are important in BL-mediated signaling in root growth. When treated with 0.1 μM BL, DAG accumulation was observed in tobacco BY-2 cell cultures labeled with fluorescent PC as early as 15 min after application. We hypothesize that at least one PC-PLC is a plant signaling enzyme in BL signal transduction and, as shown earlier, in elicitor signal transduction.
磷脂酰胆碱水解磷脂酶 C（PC-PLC）催化磷脂酰胆碱（PC）水解生成磷酸胆碱和二酰基甘油（DAG）。PC-PLC 在动物信号转导中具有悠久的历史，除了经典的磷脂酰肌醇分解磷脂酶 C（PI-PLC）外，还可生成 DAG 作为第二信使。基于与细菌 PC-PLC 的氨基酸序列相似性，在拟南芥基因组中鉴定出了 6 个假定的 PC-PLC 基因（NPC1 到 NPC6）。RT-PCR 分析显示 NPC 基因在根、茎、叶、花和角果中存在重叠表达模式。在生长素处理的 P（NPC3）：GUS 和 P（NPC4）：GUS 幼苗中，根、叶和茎中可见 GUS 活性明显增加，在油菜素内酯（BL）处理的幼苗中则较弱。P（NPC4）：GUS 幼苗也对细胞分裂素作出反应，表现为幼叶中 GUS 活性增加。与野生型相比，T-DNA 插入敲除 NPC3 和 NPC4 的拟南芥主根较短，低浓度 BL 时侧根密度较低，但对外源 0.05-1.0 μM BL 响应时侧根密度增加。BL 诱导的 TCH4 和 LRX2 的表达受到影响，而 CPD（BL 生物合成基因）的抑制不受影响，CPD 参与细胞扩张。这些观察结果表明 NPC3 和 NPC4 在 BL 介导的根生长信号转导中发挥重要作用。用 0.1 μM BL 处理后，用荧光 PC 标记的烟草 BY-2 细胞培养物中在处理后 15 分钟即可观察到 DAG 积累。我们假设至少有一种 PC-PLC 是 BL 信号转导中的植物信号酶，正如早期研究表明的那样，在激发子信号转导中也是如此。
