Kerchev Pavel, Mühlenbock Per, Denecker Jordi, Morreel Kris, Hoeberichts Frank A, Van Der Kelen Katrien, Vandorpe Micheal, Nguyen Long, Audenaert Dominique, Van Breusegem Frank
Plant Cell Environ. 2015 Feb;38(2):253-65. doi: 10.1111/pce.12250.
The high metabolic flux through photorespiration constitutes a significant part of the carbon cycle. Although the major enzymatic steps of the photorespiratory pathway are well characterized, little information is available on the functional significance of photorespiration beyond carbon recycling. Particularly important in this respect is the peroxisomal catalase activity which removes photorespiratory H2O2 generated during the oxidation of glycolate to glyoxylate, thus maintaining the cellular redox homeostasis governing the perception, integration and execution of stress responses. By performing a chemical screen, we identified 34 small molecules that alleviate the negative effects of photorespiration in Arabidopsis thaliana mutants lacking photorespiratory catalase (cat2). The chlorophyll fluorescence parameter photosystem II maximum efficiency (Fv′/Fm′) was used as a high-throughput readout. The most potent chemical that could rescue the photorespiratory phenotype of cat2 is a pro-auxin that contains a synthetic auxin-like substructure belonging to the phenoxy herbicide family, which can be released in planta. The naturally occurring indole-3-acetic acid (IAA) and other chemically distinct synthetic auxins also inhibited the photorespiratory-dependent cell death in cat2 mutants, implying a role for auxin signalling in stress tolerance.
光呼吸过程中的高代谢通量构成了碳循环的重要组成部分。尽管光呼吸途径的主要酶促步骤已得到充分表征，但关于光呼吸在碳循环之外的功能意义的信息却很少。在这方面特别重要的是过氧化物酶体过氧化氢酶活性，它能去除乙醇酸氧化为乙醛酸过程中产生的光呼吸H2O2，从而维持细胞氧化还原稳态，这种稳态控制着应激反应的感知、整合和执行。通过化学筛选，我们鉴定出34种小分子，它们能减轻拟南芥缺乏光呼吸过氧化氢酶（cat2）突变体中光呼吸的负面影响。叶绿素荧光参数光系统II最大效率（Fv′/Fm′）被用作高通量读数。能够挽救cat2光呼吸表型的最有效化学物质是一种前体生长素，它含有属于苯氧基除草剂家族的合成生长素样亚结构，可在植物体内释放。天然存在的吲哚-3-乙酸（IAA）和其他化学性质不同的合成生长素也抑制了cat2突变体中光呼吸依赖性细胞死亡，这意味着生长素信号传导在胁迫耐受性中发挥作用。
