UPS, UMR 5546, Surfaces Cellulaires et Signalisation chez les Végétaux, Université de Toulouse, BP 42617, F-31326 Castanet-Tolosan, France.
Mol Plant. 2011 Mar;4(2):310-8. doi: 10.1093/mp/ssq077. Epub 2011 Jan 3.
Sphinganine or dihydrosphingosine (d18:0, DHS), one of the most abundant free sphingoid Long Chain Base (LCB) in plants, has been recently shown to induce both cytosolic and nuclear calcium transient increases and a correlated Programmed Cell Death (PCD) in tobacco BY-2 cells. In this study, in order to get deeper insight into the LCB signaling pathway leading to cell death, the putative role of Reactive Oxygen Species (ROS) has been investigated. We show that DHS triggers a rapid dose-dependent production of H₂O₂ that is blocked by diphenyleniodonium (DPI), indicating the involvement of NADPH oxidase(s) in the process. In addition, while DPI does not block DHS-induced calcium increases, the ROS production is inhibited by the broad spectrum calcium channel blocker lanthanum (La³+). Therefore, ROS production occurs downstream of DHS-induced Ca²+ transients. Interestingly, DHS activates expression of defense-related genes that is inhibited by both La³+ and DPI. Since DPI does not prevent DHS-induced cell death, these results strongly indicate that DHS-induced H₂O₂ production is not implicated in PCD mechanisms but rather would be associated to basal cell defense mechanisms.
神经醇或二氢神经鞘氨醇（d18:0，DHS）是植物中含量最丰富的游离神经鞘氨醇长链碱基（LCB）之一，最近已被证明可诱导烟草 BY-2 细胞的细胞质和核内钙瞬变增加，并伴有程序性细胞死亡（PCD）。在这项研究中，为了更深入地了解导致细胞死亡的 LCB 信号通路，研究了活性氧物种（ROS）的假定作用。我们表明 DHS 触发了快速剂量依赖性的 H₂O₂产生，该过程被二苯并碘鎓（DPI）阻断，表明 NADPH 氧化酶（s）参与了该过程。此外，虽然 DPI 不阻断 DHS 诱导的钙增加，但广谱钙通道阻滞剂镧（La³+）抑制了 ROS 的产生。因此，ROS 的产生发生在 DHS 诱导的 Ca²+瞬变之后。有趣的是，DHS 激活了防御相关基因的表达，而 La³+和 DPI 都抑制了这种表达。由于 DPI 不能阻止 DHS 诱导的细胞死亡，这些结果强烈表明 DHS 诱导的 H₂O₂产生与 PCD 机制无关，而是与基础细胞防御机制相关。
