Legendre L, Yueh Y G, Crain R, Haddock N, Heinstein P F, Low P S
Department of Chemistry, Purdue University, West Lafayette, Indiana 47907.
J Biol Chem. 1993 Nov 25;268(33):24559-63.
Although phospholipase C hydrolysis of polyphosphoinositides constitutes one of the major second messenger pathways in animal cells, its participation in signal transduction in higher plants has not been established. To determine whether activation of phosphatidylinositol-directed phospholipase C might be involved in signaling the elicitor-induced oxidative burst in plants, suspension-cultured soybean cells were treated with two stimulants of the H2O2 burst and examined for polyphosphoinositide turnover. Both polygalacturonic acid elicitor and the G protein activator, mastoparan, promoted a transient increase in inositol 1,4,5-trisphosphate (IP3) content that exceeded basal IP3 levels (0.9 +/- 0.4 pmol of IP3/10(6) cells, n = 28) by 2.6- and 7-fold, respectively. In each case, intracellular IP3 content reached a maximum at 1 min post-stimulation and declined to near basal levels during the subsequent 5-10 min. Neomycin sulfate, an inhibitor of polyphosphoinositide hydrolysis, blocked the IP3 transient, and Mas-17, an inactive analogue of mastoparan, induced no change in IP3. Thin layer chromatography of lipid extracts of the soybean cells corroborated the above results by revealing a rapid decrease in phosphatidyl-inositol monophosphate and phosphatidylinositol 4,5-bisphosphate following polygalacturonic acid elicitor and mastoparan (but not Mas-17) stimulation. Since the rise in IP3 preceded H2O2 production and since neomycin sulfate inhibited the appearance of both, we hypothesize that phospholipase C activation might constitute one pathway by which elicitors trigger the soybean oxidative burst.
尽管磷脂酶C对多磷酸肌醇的水解作用构成了动物细胞中主要的第二信使途径之一，但其在高等植物信号转导中的作用尚未得到证实。为了确定磷脂酰肌醇定向的磷脂酶C的激活是否参与植物中激发子诱导的氧化爆发信号转导，用两种H2O2爆发刺激剂处理悬浮培养的大豆细胞，并检测多磷酸肌醇的周转情况。聚半乳糖醛酸激发子和G蛋白激活剂马斯托帕罗均促进了肌醇1,4,5-三磷酸（IP3）含量的短暂增加，分别比基础IP3水平（0.9±0.4 pmol IP3/10(6)个细胞，n = 28）高出2.6倍和7倍。在每种情况下，细胞内IP3含量在刺激后1分钟达到最大值，并在随后的5 - 10分钟内降至接近基础水平。多磷酸肌醇水解抑制剂硫酸新霉素阻断了IP3的瞬变，而马斯托帕罗的无活性类似物Mas - 17未引起IP3的变化。大豆细胞脂质提取物的薄层层析通过显示聚半乳糖醛酸激发子和马斯托帕罗（而非Mas - 17）刺激后磷脂酰肌醇单磷酸和磷脂酰肌醇4,5 - 二磷酸的快速减少，证实了上述结果。由于IP3的升高先于H2O2的产生，且硫酸新霉素抑制了两者的出现，我们推测磷脂酶C的激活可能是激发子触发大豆氧化爆发的一条途径。
