Arabidopsis plants overexpressing glycolate oxidase in chloroplasts (GO5) and loss-of-function mutants of the major peroxisomal catalase isoform, cat2-2, produce increased hydrogen peroxide (H2 O2 ) amounts from the respective organelles when subjected to photorespiratory conditions like increased light intensity. Here, we have investigated if and how the signaling processes triggered by H2 O2 production in response to shifts in environmental conditions and the concomitant induction of indole phytoalexin biosynthesis in GO5 affect susceptibility towards the hemibiotrophic fungus Colletotrichum higginsianum. Combining histological, biochemical, and molecular assays, we found that the accumulation of the phytoalexin camalexin was comparable between GO genotypes and cat2-2 in the absence of pathogen. Compared with wild-type, GO5 showed improved resistance after light-shift-mediated production of H2 O2 , whereas cat2-2 became more susceptible and allowed significantly more pathogen entry. Unlike GO5, cat2-2 suffered from severe oxidative stress after light shifts, as indicated by glutathione pool size and oxidation state. We discuss a connection between elevated oxidative stress and dampened induction of salicylic acid mediated defense in cat2-2. Genetic analyses demonstrated that induced resistance of GO5 is dependent on WRKY33, but not on camalexin production. We propose that indole carbonyl nitriles might play a role in defense against C. higginsianum.

中文翻译：

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拟南芥叶绿体中活性氧的剂量可以通过诱导WRKY33来提高对炭疽菌的抗性。

拟南芥植物在叶绿体中过表达乙醇酸氧化酶（GO5）和主要过氧化物酶体过氧化氢酶同工酶cat2-2的功能丧失突变体，在受到光呼吸条件（例如光强度增加）的作用下，各自细胞器产生的过氧化氢（H2 O2）量增加。 。在这里，我们研究了是否以及如何由H2 O2产生触发的信号传导过程，以响应环境条件的变化以及GO5中吲哚植物抗毒素生物合成的诱导，从而影响对半生营养真菌希氏炭疽菌的易感性。结合组织学，生化和分子分析，我们发现在没有病原体的情况下，GO基因型和cat2-2之间植物抗毒素camalexin的积累是可比的。与野生型相比，GO5在光移介导的H2 O2产生后显示出更高的抗性，而cat2-2变得更易感，并允许更多的病原体进入。与GO5不同，如谷胱甘肽池大小和氧化态所示，cat2-2在光移后会遭受严重的氧化应激。我们讨论了升高的氧化应激与水杨酸介导的防御在cat2-2中的联系。遗传分析表明，GO5的诱导抗性依赖于WRKY33，而不依赖于Camalexin的产生。我们建议吲哚羰基腈可能在防御棉铃虫中发挥作用。如谷胱甘肽池大小和氧化态所指示。我们讨论了升高的氧化应激与水杨酸介导的防御在cat2-2中的联系。遗传分析表明，GO5的诱导抗性依赖于WRKY33，而不依赖于Camalexin的产生。我们建议吲哚羰基腈可能在防御棉铃虫中发挥作用。如谷胱甘肽池大小和氧化态所指示。我们讨论了升高的氧化应激与水杨酸介导的防御在cat2-2中的联系。遗传分析表明，GO5的诱导抗性依赖于WRKY33，而不依赖于Camalexin的产生。我们建议吲哚羰基腈可能在防御棉铃虫中发挥作用。