Drought stress in plants leads to inhibition of photosynthesis and respiration, accumulation of reactive oxygen species (ROS), and reprogramming of gene expression. Here, we established that the tomato (Solanum lycopersicum) WHIRLY2 (SlWHY2) gene, which encodes a mitochondrial single-stranded DNA-binding protein, was significantly induced by drought stress. Under drought conditions, SlWHY2 RNAi plants showed more wilting and lower fresh weight, chlorophyll content, quantum yield of photosystem I (PSI; YI), and maximal photochemical efficiency of PSII (Fv/Fm) than the wild type (WT). Drought treatment also caused the SlWHY2 RNAi lines to accumulate more ROS than the WT, and the silenced lines had lower AOX (alternative oxidase) activity. As expected, the mitochondrial membrane potential (MMP) was less stable in the SlWHY2 RNAi lines. The expression levels of seven genes in the mitochondrial genome (SYCF15, NAD7, NAD4, COS2, COX1, COX2, and COX3) were decreased even more in the SlWHY2 RNAi lines than they were in the WT under drought stress. SlWHY2 interacted directly in vivo and in vitro with SlRECA2, a mitochondrial recombinase A that is important for mitochondrial DNA recombination and repair. These results suggest that SlWHY2 plays an essential role in maintaining mitochondrial function and enhancing drought tolerance in tomato.

中文翻译：

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SlWHY2与SlRECA2相互作用以维持番茄干旱胁迫下的线粒体功能

植物的干旱胁迫导致光合作用和呼吸作用的抑制、活性氧 (ROS) 的积累以及基因表达的重编程。在这里，我们确定了干旱胁迫显着诱导了番茄 (Solanum lycopersicum) WHIRLY2 (SlWHY2) 基因，该基因编码线粒体单链 DNA 结合蛋白。在干旱条件下，SlWHY2 RNAi 植物比野生型 (WT) 表现出更多的枯萎和更低的鲜重、叶绿素含量、光系统 I (PSI; YI) 的量子产量和 PSII (Fv/Fm) 的最大光化学效率。干旱处理还导致 SlWHY2 RNAi 系比 WT 积累更多的 ROS，并且沉默的系具有较低的 AOX（替代氧化酶）活性。正如预期的那样，线粒体膜电位 (MMP) 在 SlWHY2 RNAi 系中不太稳定。在干旱胁迫下，SlWHY2 RNAi 系中线粒体基因组中 7 个基因（SYCF15、NAD7、NAD4、COS2、COX1、COX2 和 COX3）的表达水平比它们在 WT 中的降低更多。SlWHY2 在体内和体外与 SlRECA2 直接相互作用，SlRECA2 是一种对线粒体 DNA 重组和修复很重要的线粒体重组酶 A。这些结果表明 SlWHY2 在维持线粒体功能和增强番茄耐旱性方面发挥着重要作用。线粒体重组酶 A，对线粒体 DNA 重组和修复很重要。这些结果表明 SlWHY2 在维持线粒体功能和增强番茄耐旱性方面发挥着重要作用。线粒体重组酶 A，对线粒体 DNA 重组和修复很重要。这些结果表明 SlWHY2 在维持线粒体功能和增强番茄耐旱性方面发挥着重要作用。