Jansen M A, van den Noort R E, Tan M Y, Prinsen E, Lagrimini L M, Thorneley R N
Department of Biological Chemistry, John Innes Centre, Norwich Research Park, Norwich NR4 7UH, United Kingdom.
Plant Physiol. 2001 Jul;126(3):1012-23. doi: 10.1104/pp.126.3.1012.
We have studied the mechanism of UV protection in two duckweed species (Lemnaceae) by exploiting the UV sensitivity of photosystem II as an in situ sensor for radiation stress. A UV-tolerant Spirodela punctata G.F.W. Meyer ecotype had significantly higher indole-3-acetic acid (IAA) levels than a UV-sensitive ecotype. Parallel work on Lemna gibba mutants suggested that UV tolerance is linked to IAA degradation rather than to levels of free or conjugated IAA. This linkage is consistent with a role for class III phenolic peroxidases, which have been implicated both in the degradation of IAA and the cross-linking of various UV-absorbing phenolics. Biochemical analysis revealed increased activity of a specific peroxidase isozyme in both UV-tolerant duckweed lines. The hypothesis that peroxidases play a role in UV protection was tested in a direct manner using genetically modified tobacco (Nicotiana sylvestris). It was found that increased activity of the anionic peroxidase correlated with increased tolerance to UV radiation as well as decreased levels of free auxin. We conclude that phenol-oxidizing peroxidases concurrently contribute to UV protection as well as the control of leaf and plant architecture.
我们利用光系统II的紫外线敏感性作为辐射胁迫的原位传感器，研究了两种浮萍科植物的紫外线防护机制。耐紫外线的紫萍生态型的吲哚-3-乙酸（IAA）水平显著高于对紫外线敏感的生态型。对少根紫萍突变体的平行研究表明，紫外线耐受性与IAA降解有关，而非与游离或结合态IAA水平有关。这种联系与III类酚类过氧化物酶的作用一致，该酶既参与IAA的降解，也参与各种紫外线吸收酚类的交联。生化分析显示，两种耐紫外线浮萍品系中一种特定过氧化物酶同工酶的活性均有所增加。我们使用转基因烟草（林烟草）直接验证了过氧化物酶在紫外线防护中发挥作用的假设。结果发现，阴离子过氧化物酶活性的增加与对紫外线辐射耐受性的提高以及游离生长素水平的降低相关。我们得出结论，酚氧化过氧化物酶同时有助于紫外线防护以及叶片和植株结构的调控。
