Commonwealth Scientific and Industrial Research Organisation Plant Industry, Wembley, WA 6913, Australia.
Proc Natl Acad Sci U S A. 2011 Jun 28;108(26):10768-73. doi: 10.1073/pnas.1016060108. Epub 2011 Jun 13.
Mitochondria are both a source of ATP and a site of reactive oxygen species (ROS) production. However, there is little information on the sites of mitochondrial ROS (mROS) production or the biological role of such mROS in plants. We provide genetic proof that mitochondrial complex II (Complex II) of the electron transport chain contributes to localized mROS that regulates plant stress and defense responses. We identify an Arabidopsis mutant in the Complex II subunit, SDH1-1, through a screen for mutants lacking GSTF8 gene expression in response to salicylic acid (SA). GSTF8 is an early stress-responsive gene whose transcription is induced by biotic and abiotic stresses, and its expression is commonly used as a marker of early stress and defense responses. Transcriptional analysis of this mutant, disrupted in stress responses 1 (dsr1), showed that it had altered SA-mediated gene expression for specific downstream stress and defense genes, and it exhibited increased susceptibility to specific fungal and bacterial pathogens. The dsr1 mutant also showed significantly reduced succinate dehydrogenase activity. Using in vivo fluorescence assays, we demonstrated that root cell ROS production occurred primarily from mitochondria and was lower in the mutant in response to SA. In addition, leaf ROS production was lower in the mutant after avirulent bacterial infection. This mutation, in a conserved region of SDH1-1, is a unique plant mitochondrial mutant that exhibits phenotypes associated with lowered mROS production. It provides critical insights into Complex II function with implications for understanding Complex II's role in mitochondrial diseases across eukaryotes.
线粒体既是 ATP 的来源，也是活性氧物种 (ROS) 产生的场所。然而，关于线粒体 ROS（mROS）产生的部位或此类 mROS 在植物中的生物学作用的信息很少。我们提供了遗传证据，证明电子传递链中的线粒体复合物 II（复合物 II）有助于局部 mROS 的产生，从而调节植物的应激和防御反应。我们通过筛选对水杨酸 (SA) 无 GSTF8 基因表达的突变体，鉴定出拟南芥中复合物 II 亚基 SDH1-1 的突变体。GSTF8 是一种早期应激反应基因，其转录受生物和非生物胁迫诱导，其表达通常用作早期应激和防御反应的标志物。该突变体（在应激反应 1 中中断，dsr1）的转录分析表明，它改变了 SA 介导的特定下游应激和防御基因的表达，并且对特定真菌和细菌病原体的敏感性增加。dsr1 突变体的琥珀酸脱氢酶活性也显著降低。通过体内荧光测定，我们证明根细胞 ROS 的产生主要来自线粒体，并且在突变体中对 SA 的反应较低。此外，在无毒细菌感染后，突变体叶片中的 ROS 产生较低。该突变位于 SDH1-1 的保守区域，是一种独特的植物线粒体突变体，表现出与降低 mROS 产生相关的表型。它为复合物 II 的功能提供了关键的见解，并对理解复合物 II 在真核生物中线粒体疾病中的作用具有重要意义。
