Ranieri A, Castagna A, Baldan B, Soldatini G F
Dipartimento Chimica e Biotecnologie Agrarie, Università degli Studi di Pisa, Via del Borghetto 80, 56124 Pisa, Italy.
J Exp Bot. 2001 Jan;52(354):25-35.
The response of both specific (ascorbate peroxidase, APX) and unspecific (POD) peroxidases and H(2)O(2) content of sunflower plants (Helianthus annuus L. cv. Hor) grown hydroponically with (C) or without (-Fe) iron in the nutrient solution were analysed to verify whether iron deficiency led to cell oxidative status. In -Fe leaves a significant increase of H(2)O(2) content was detected, a result confirmed by electron microscopy analysis. As regards extracellular peroxidases, while APX activity significantly decreased, no change was observed in either soluble guaiacol or syringaldazine-dependent POD activity following iron starvation. Moreover, guaiacol-dependent POD activity was found to decrease in both ionically and covalently-cell-wall bound fractions, while syringaldazine-POD activity decreased only in the covalently-bound fraction. At the intracellular level both guaiacol-POD and APX activities underwent a significant decrease. The overall reduction of peroxidase activity was confirmed by the electrophoretic separation of POD isoforms and, at the extracellular level, by cytochemical localization of peroxidases by diaminobenzidine staining. The electrophoretic separation, besides quantitative differences, also revealed quantitative changes, particularly evident for ionically and covalently-bound fractions. Therefore, in sunflower plants, iron deficiency seems to affect the different peroxidase isoenzymes to different extents and to induce a secondary oxidative stress, as indicated by the increased levels of H(2)O(2). However, owing to the almost completely lack of catalytic iron capable of triggering the Fenton reaction, iron-deficient sunflower plants are probably still sufficiently protected against oxidative stress.
分析了水培生长的向日葵植株（向日葵品种Hor）在营养液中有（C）或无（-Fe）铁的情况下，特异性（抗坏血酸过氧化物酶，APX）和非特异性（POD）过氧化物酶的反应以及H₂O₂含量，以验证缺铁是否会导致细胞氧化状态。在缺铁叶片中检测到H₂O₂含量显著增加，这一结果通过电子显微镜分析得到证实。关于细胞外过氧化物酶，虽然APX活性显著降低，但缺铁后可溶性愈创木酚或丁香醛连氮依赖性POD活性均未观察到变化。此外，发现愈创木酚依赖性POD活性在离子结合和共价结合细胞壁部分均降低，而丁香醛连氮-POD活性仅在共价结合部分降低。在细胞内水平，愈创木酚-POD和APX活性均显著降低。通过POD同工酶的电泳分离以及在细胞外水平通过二氨基联苯胺染色对过氧化物酶进行细胞化学定位，证实了过氧化物酶活性的总体降低。电泳分离除了显示定量差异外，还揭示了定量变化，在离子结合和共价结合部分尤为明显。因此，在向日葵植株中，缺铁似乎对不同的过氧化物酶同工酶有不同程度的影响，并诱导了继发性氧化应激，H₂O₂水平升高表明了这一点。然而，由于几乎完全缺乏能够引发芬顿反应的催化铁，缺铁的向日葵植株可能仍能充分抵御氧化应激。
