Heyno Eiri, Gross Christine M, Laureau Constance, Culcasi Marcel, Pietri Sylvia, Krieger-Liszkay Anja
Commissariat à l'Energie Atomique (CEA), iBiTecS, CNRS URA 2096, Service de Bioénergétique Biologie Structurale et Mécanisme, 91191 Gif-sur-Yvette Cedex, France.
J Biol Chem. 2009 Nov 6;284(45):31174-80. doi: 10.1074/jbc.M109.021667. Epub 2009 Sep 9.
Photoinhibition and production of reactive oxygen species were studied in tobacco plants overexpressing the plastid terminal oxidase (PTOX). In high light, these plants was more susceptible to photoinhibition than wild-type plants. Also oxygen-evolving activity of isolated thylakoid membranes from the PTOX-overexpressing plants was more strongly inhibited in high light than in thylakoids from wild-type plants. In contrast in low light, in the PTOX overexpressor, the thylakoids were protected against photoinhibition while in wild type they were significantly damaged. The production of superoxide and hydroxyl radicals was shown by EPR spin-trapping techniques in the different samples. Superoxide and hydroxyl radical production was stimulated in the overexpressor. Two-thirds of the superoxide production was maintained in the presence of DNP-INT, an inhibitor of the cytochrome b(6)f complex. No increase of the SOD content was observed in the overexpressor compared with the wild type. We propose that superoxide is produced by PTOX in a side reaction and that PTOX can only act as a safety valve under stress conditions when the generated superoxide is detoxified by an efficient antioxidant system.
在过表达质体末端氧化酶（PTOX）的烟草植株中研究了光抑制和活性氧的产生。在高光条件下，这些植株比野生型植株更容易受到光抑制。此外，与野生型植株的类囊体相比，高光条件下过表达PTOX植株分离出的类囊体的放氧活性受到更强的抑制。相反，在弱光条件下，过表达PTOX植株的类囊体受到光抑制保护，而野生型植株的类囊体则受到显著损伤。通过电子顺磁共振自旋捕获技术显示了不同样品中超氧阴离子和羟基自由基的产生。过表达植株中超氧阴离子和羟基自由基的产生受到刺激。在存在细胞色素b（6）f复合体抑制剂DNP-INT的情况下，三分之二的超氧阴离子产生得以维持。与野生型相比，过表达植株中未观察到超氧化物歧化酶（SOD）含量增加。我们提出，超氧阴离子是由PTOX在副反应中产生的，并且当产生的超氧阴离子被高效抗氧化系统解毒时，PTOX仅在胁迫条件下起安全阀的作用。
