Huang Ai-Xia, She Xiao-Ping, Cao Bin, Zhang Bei, Mu Juan, Zhang Shao-Jie
Key Laboratory of Medicinal Plant Resource and Natural Pharmaceutical Chemistry of Ministry of Education, College of Life Sciences, Shaanxi Normal University, Xi'an 710062, China.
Physiol Plant. 2009 May;136(1):45-56. doi: 10.1111/j.1399-3054.2009.01212.x. Epub 2009 Feb 12.
Water deficit and the resulting osmotic stress affect stomatal movement. There are two types of signals, hydraulic and chemical signals, involving in the regulation of stomatal behavior responses to osmotic stress. Compared with the chemical signals, little has been known about the hydraulic signals and the corresponding signal transduction network and regulatory mechanisms. Here, using an epidermal-strip bioassay and laser-scanning confocal microscopy, we provide evidence that nitric oxide (NO) generation in Vicia faba guard cells can be induced by hydraulic signals. We used polyethylene glycol (PEG) 600 to simulate hypertonic conditions. This hydraulic signal led to stomatal closure and rapid promotion of NO production in guard cells. The effects were decreased by NO scavenger 2-(4-carboxyphenyl)-4,4,5, 5-tetramethylimidazoline-1-oxyl-3-oxide (c-PTIO) and NO synthase (Enzyme Commission 1.14.13.39) inhibitor N(G)-nitro-L-Arg-methyl ester (L-NAME). These results indicate that PEG 6000 induces stomatal closure by promoting NO production. Cytochalasin B (CB) inhibited stomatal closure induced by PEG 6000 but did not prevent the increase of endogenous NO levels, indicating that microfilaments polymerization participate in stomatal closure induced by PEG 6000, and may act downstream of NO signaling. In addition, big vacuoles split into many small vacuoles were observed in response to PEG 6000 and sodium nitroprusside (SNP) treatment, and CB inhibited these changes of vacuoles, the stomatal closure was also been inhibited. Collectively, these results suggest that the stomatal closure induced by PEG 6000 may be intimately associated with NO levels, reorganization of actin filaments and the changes of vacuoles, showing a crude outline of guard-cells signaling process in response to hydraulic signals.
水分亏缺及由此产生的渗透胁迫会影响气孔运动。有两种信号，即水力信号和化学信号，参与调节气孔行为对渗透胁迫的响应。与化学信号相比，人们对水力信号及其相应的信号转导网络和调控机制了解甚少。在此，我们使用表皮条生物测定法和激光扫描共聚焦显微镜，提供证据表明蚕豆保卫细胞中的一氧化氮（NO）生成可由水力信号诱导。我们使用聚乙二醇（PEG）600来模拟高渗条件。这种水力信号导致气孔关闭并迅速促进保卫细胞中NO的产生。NO清除剂2-(4-羧基苯基)-4,4,5,5-四甲基咪唑啉-1-氧基-3-氧化物（c-PTIO）和NO合酶（酶委员会1.14.13.39）抑制剂N(G)-硝基-L-精氨酸甲酯（L-NAME）可降低这些效应。这些结果表明PEG 6000通过促进NO生成来诱导气孔关闭。细胞松弛素B（CB）抑制PEG 6000诱导的气孔关闭，但不阻止内源性NO水平的升高，表明微丝聚合参与PEG 6000诱导的气孔关闭，且可能作用于NO信号的下游。此外，观察到响应PEG 6000和硝普钠（SNP）处理时，大液泡分裂成许多小液泡，而CB抑制了这些液泡变化，同时也抑制了气孔关闭。总的来说，这些结果表明PEG 6000诱导的气孔关闭可能与NO水平、肌动蛋白丝的重组以及液泡变化密切相关，显示出保卫细胞响应水力信号的信号传导过程的大致轮廓。
