Quiroga M, Guerrero C, Botella M A, Barceló A, Amaya I, Medina M I, Alonso F J, de Forchetti S M, Tigier H, Valpuesta V
Departamento de Biología Molecular, Universidad Nacional de Río Cuarto, 5800 Río Cuarto (Cba), Argentina.
Plant Physiol. 2000 Apr;122(4):1119-27. doi: 10.1104/pp.122.4.1119.
The last step in the synthesis of lignin and suberin has been proposed to be catalyzed by peroxidases, although other proteins may also be involved. To determine which peroxidases are involved in the synthesis of lignin and suberin, five peroxidases from tomato (Lycopersicon esculentum) roots, representing the majority of the peroxidase activity in this organ, have been partially purified and characterized kinetically. The purified peroxidases with isoelectric point (pI) values of 3.6 and 9.6 showed the highest catalytic efficiency when the substrate used was syringaldazine, an analog of lignin monomer. Using a combination of transgenic expression and antibody recognition, we now show that the peroxidase pI 9.6 is probably encoded by TPX1, a tomato peroxidase gene we have previously isolated. In situ RNA hybridization revealed that TPX1 expression is restricted to cells undergoing synthesis of lignin and suberin. Salt stress has been reported to induce the synthesis of lignin and/or suberin. This stress applied to tomato caused changes in the expression pattern of TPX1 and induced the TPX1 protein. We propose that the TPX1 product is involved in the synthesis of lignin and suberin.
尽管其他蛋白质可能也参与其中，但有人提出过氧化物酶催化木质素和木栓质合成的最后一步。为了确定哪些过氧化物酶参与木质素和木栓质的合成，已对来自番茄（Lycopersicon esculentum）根的五种过氧化物酶进行了部分纯化，并对其动力学特性进行了表征，这五种过氧化物酶代表了该器官中大部分的过氧化物酶活性。当使用丁香醛连氮（一种木质素单体类似物）作为底物时，纯化后的等电点（pI）值为3.6和9.6的过氧化物酶显示出最高的催化效率。通过转基因表达和抗体识别相结合的方法，我们现在表明过氧化物酶pI 9.6可能由TPX1编码，TPX1是我们之前分离出的一个番茄过氧化物酶基因。原位RNA杂交显示TPX1的表达仅限于正在进行木质素和木栓质合成的细胞。据报道，盐胁迫会诱导木质素和/或木栓质的合成。施加于番茄的这种胁迫导致了TPX1表达模式的变化并诱导了TPX1蛋白的产生。我们认为TPX1产物参与了木质素和木栓质的合成。
