Song Xi-Gui, She Xiao-Ping, He Jun-Min, Huang Chen, Song Tu-Sheng
School of Life Sciences, Shaanxi Normal University, Xi'an 710062, People's Republic of China.
Department of Biology and Genetics, Medical School of Xi'an Jiaotong University, Xi'an 710062, People's Republic of China.
Funct Plant Biol. 2006 Jun;33(6):573-583. doi: 10.1071/FP05232.
Previous studies have shown that cytokinins and auxins can induce the opening of stomata. However, the mechanism of stomatal opening caused by cytokinins and auxins remains unclear. The purpose of this paper is to investigate the relationship between hydrogen peroxide (HO) levels in guard cells and stomatal opening induced by cytokinins and auxins in Vicia faba. By means of stomatal bioassay and laser-scanning confocal microscopy, we provide evidence that cytokinins and auxins reduced the levels of HO in guard cells and induced stomatal opening in darkness. Additionally, cytokinins not only reduced exogenous HO levels in guard cells caused by exposure to light, but also abolished HO that had been generated during a dark period, and promoted stomatal opening, as did ascorbic acid (ASA, an important reducing substrate for HO removal). However, unlike cytokinins, auxins did not reduce exogenous HO, did not abolish HO that had been generated in the dark, and therefore did not promote reopening of stoma induced to close in the dark. The above-mentioned effects of auxins were similar to that of diphenylene iodonium (DPI, an inhibitor of the HO-generating enzyme NADPH oxidase). Taken together our results indicate that cytokinins probably reduce the levels of HO in guard cells by scavenging, whereas auxins limit HO levels through restraining HO generation, inducing stomatal opening in darkness.
先前的研究表明，细胞分裂素和生长素可诱导气孔开放。然而，细胞分裂素和生长素导致气孔开放的机制仍不清楚。本文的目的是研究蚕豆保卫细胞中过氧化氢（H₂O₂）水平与细胞分裂素和生长素诱导的气孔开放之间的关系。通过气孔生物测定和激光扫描共聚焦显微镜，我们提供了证据表明，细胞分裂素和生长素降低了保卫细胞中H₂O₂的水平，并在黑暗中诱导气孔开放。此外，细胞分裂素不仅降低了因光照导致的保卫细胞中外源H₂O₂的水平，还消除了在黑暗期产生的H₂O₂，并促进了气孔开放，抗坏血酸（ASA，一种用于去除H₂O₂的重要还原底物）也有同样的作用。然而，与细胞分裂素不同，生长素不能降低外源H₂O₂，不能消除在黑暗中产生的H₂O₂，因此不能促进在黑暗中诱导关闭的气孔重新开放。生长素的上述作用与二苯基碘鎓（DPI，一种H₂O₂生成酶NADPH氧化酶的抑制剂）相似。综上所述，我们的结果表明，细胞分裂素可能通过清除作用降低保卫细胞中H₂O₂的水平，而生长素则通过抑制H₂O₂的产生来限制H₂O₂水平，从而在黑暗中诱导气孔开放。
