ABA-induced hydrogen peroxide generation in guard cells of Vicia faba
2000
Miao Yuchen | Song Chunpeng | Dong Facai (Henan Univ., Kaifeng (China). Dept. of Biology) | Wang Xuechen
Changes in H2O2 generation in guard cells of Vicia faba induced by ABA were measured by using fluorescence probe, 8-hydroxypyrene-1,3,6-trisulfonic acid (HPTS). Examination of epidermis peel was performed using a laser scanning confocal microscope and spectrofluorometer, set to an excitation light of 405 nm and an emission light of 512 nm. The fluorescence image before stimulation showed dye accumulation in guard cells, distributed homogeneously, with the exception of the chloroplast and nucleus where the fluorescence intensity was stronger, and there was almost no fluorescence in the epidermal cells (Plate I). We also showed that the fluorescence was not significantly fading throughout the experiment. The retention time was long enough for analyses. When guard cells were treated with ABA, fluorescence quenching of HPTS occurred. A does-dependent study of the ABA-induced oxidative burst was observed, in which both the magnitude and rate of dye quenching was directly related to the concentration of ABA (Fig. 2). And the treatment of the guard cells with catalase of 100 units/ml nearly completely obliterated the quenching reaction induced by ABA 10 mumol/L (final concentration). Furthermore, when H2O2 10 mumol/L (final concentration) was added to the suspension after above treatment caused little reduction in HPTS fluorescence (Fig. 3). The results obtained by laser scanning confocal microscopy suggested that addition of exogenous ABA resulted in a rapid decrease in fluorescene in most cellular compartments of the guard cells (Plate I). Above data support the hypothesis that H2O2 is involved in the signal transduction pathway of ABA-induced stomatal closure
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