Division of Plant Biology, Department of Biosciences, Viikki Plant Science Centre, University of Helsinki, 00014, Helsinki, Finland.
Unit of Plant Molecular Cell Biology, Institute for Biology I, RWTH Aachen University, 52056, Aachen, Germany.
Plant Cell Environ. 2018 Apr;41(4):782-796. doi: 10.1111/pce.13144. Epub 2018 Feb 22.
The atmospheric pollutant ozone (O ) is a strong oxidant that causes extracellular reactive oxygen species (ROS) formation, has significant ecological relevance, and is used here as a non-invasive ROS inducer to study plant signalling. Previous genetic screens identified several mutants exhibiting enhanced O sensitivity, but few with enhanced tolerance. We found that loss-of-function mutants in Arabidopsis MLO2, a gene implicated in susceptibility to powdery mildew disease, exhibit enhanced dose-dependent tolerance to O and extracellular ROS, but a normal response to intracellular ROS. This phenotype is increased in a mlo2 mlo6 mlo12 triple mutant, reminiscent of the genetic redundancy of MLO genes in powdery mildew resistance. Stomatal assays revealed that enhanced O tolerance in mlo2 mutants is not caused by altered stomatal conductance. We explored modulation of the mlo2-associated O tolerance, powdery mildew resistance, and early senescence phenotypes by genetic epistasis analysis, involving mutants with known effects on ROS sensitivity or antifungal defence. Mining of publicly accessible microarray data suggests that these MLO proteins regulate accumulation of abiotic stress response transcripts, and transcript accumulation of MLO2 itself is O responsive. In summary, our data reveal MLO2 as a novel negative regulator in plant ROS responses, which links biotic and abiotic stress response pathways.
大气污染物臭氧（O ）是一种强氧化剂，会导致细胞外活性氧物种（ROS）的形成，具有重要的生态相关性，这里将其用作非侵入性 ROS 诱导剂来研究植物信号转导。先前的遗传筛选确定了几个表现出增强的 O 敏感性的突变体，但具有增强的耐受性的突变体很少。我们发现，拟南芥 MLO2 基因的功能丧失突变体，该基因与白粉病易感性有关，表现出对 O 和细胞外 ROS 的剂量依赖性增强的耐受性，但对细胞内 ROS 的反应正常。在 mlo2 mlo6 mlo12 三重突变体中，这种表型增加，类似于 MLO 基因在白粉病抗性中的遗传冗余。气孔测定表明，mlo2 突变体中增强的 O 耐受性不是由气孔导度改变引起的。我们通过遗传上位性分析探索了与 mlo2 相关的 O 耐受性、白粉病抗性和早期衰老表型的调节，涉及已知对 ROS 敏感性或抗真菌防御有影响的突变体。对公开可用的微阵列数据的挖掘表明，这些 MLO 蛋白调节非生物胁迫反应转录物的积累，并且 MLO2 本身的转录物积累对 O 有反应。总之，我们的数据揭示了 MLO2 作为植物 ROS 反应中的一个新的负调控因子，它将生物和非生物胁迫反应途径联系起来。
