Bóka K, Orbán N, Kristóf Z
Department of Plant Anatomy, Eötvös University, Budapest, Hungary.
Protoplasma. 2007;230(1-2):89-97. doi: 10.1007/s00709-006-0225-8. Epub 2007 Feb 19.
H(2)O(2) produced in plant cells plays a dual role. In addition to its antimicrobial effect, it also acts as a secondary messenger initiating and modulating responses of plants exposed to unfavorable external signals. A suspension culture of Rubia tinctorum cells challenged with elicitors was used as a model system to investigate H(2)O(2) formation. Cellular H(2)O(2) was measured by a modified titanium(IV) method, while that in the medium was detected with scopoletin fluorescence. Localization of H(2)O(2) production at the ultrastructural level was carried out by the CeCl(3) reaction. A fungal elicitor induced H(2)O(2) production with transient maxima, the first of which appeared 4 min after treatment. Three subsequent maxima appeared in the cells up to 48 h after treatment. Exposure of cells to exogenous jasmonic acid and salicylic acid also changed the H(2)O(2) concentration maxima over 48 h; however, their timing was slightly shifted. Fungal-elicitor, jasmonic acid, and salicylic acid treatments had different effects on the H(2)O(2) concentration in the medium. Ultrastructural investigations revealed that electron-dense precipitates were present at the plasmalemma and in some nearby vesicular cytoplasmic structures 30 min after treatment. Later samples showed cytochemical-precipitate accumulation in the cell walls. These deposits appeared to be local and independent of the direction of the external signal. We could not detect the presence of H(2)O(2) in peroxisomes, mitochondria, plastids, or the central vacuolar space. Electron energy loss spectroscopy investigations distinguished between the cerium-containing precipitates and other electrondense particles, thereby proving that H(2)O(2) generation occurs locally.
植物细胞中产生的过氧化氢具有双重作用。除了其抗菌作用外，它还作为第二信使，启动并调节植物对不利外部信号的反应。以茜草细胞的悬浮培养物为模型系统，用激发子进行刺激，以研究过氧化氢的形成。细胞内的过氧化氢通过改良的钛（IV）法进行测定，而培养基中的过氧化氢则用 scopoletin 荧光法进行检测。通过 CeCl₃反应在超微结构水平上对过氧化氢的产生进行定位。一种真菌激发子诱导过氧化氢产生瞬时最大值，其中第一个最大值在处理后 4 分钟出现。在处理后的 48 小时内，细胞中又出现了三个后续最大值。将细胞暴露于外源茉莉酸和水杨酸也会在 48 小时内改变过氧化氢浓度的最大值；然而，它们出现的时间略有偏移。真菌激发子、茉莉酸和水杨酸处理对培养基中过氧化氢浓度有不同影响。超微结构研究表明，处理后 30 分钟，质膜和一些附近的囊泡状细胞质结构中存在电子致密沉淀物。后来的样本显示细胞壁中有细胞化学沉淀物积累。这些沉淀物似乎是局部的，且与外部信号的方向无关。我们在过氧化物酶体、线粒体、质体或中央液泡空间中未检测到过氧化氢的存在。电子能量损失光谱研究区分了含铈沉淀物和其他电子致密颗粒，从而证明过氧化氢的产生是局部发生的。
