Laboratory of Molecular Biology of Higher Plants, University of Geneva, Quai Ernest-Ansermet 30, Geneva 4, Switzerland.
Planta. 2013 Aug;238(2):381-95. doi: 10.1007/s00425-013-1901-5. Epub 2013 May 29.
Germination is controlled by external factors, such as temperature, water, light and by hormone balance. Recently, reactive oxygen species (ROS) have been shown to act as messengers during plant development, stress responses and programmed cell death. We analyzed the role of ROS during germination and demonstrated that ROS in addition to their role as cell wall loosening factor are essential signalling molecules in this process. Indeed, we showed that ROS are released prior to endosperm rupture, that their production is required for germination, and that class III peroxidases, as ROS level regulators, colocalized with ROS production. Among ROS, H2O2 modifies, during germination early steps, the expression of genes encoding for enzymes regulating ROS levels. This pointing out a regulatory feedback loop for ROS production. Measurements of endogenous levels of ROS following application of GA and ABA suggested that ABA inhibits germination by repressing ROS accumulation, and that, conversely, GA triggers germination by promoting an increase of ROS levels. We followed the early visible steps of germination (testa and endosperm rupture) in Arabidopsis seeds treated by specific ROS scavengers and as the light quality perception is necessary for a regular germination, we examined the germination in presence of exogenous H2O2 in different light qualities. H2O2 either promoted germination or repressed germination depending on the light wavelengths, showing that H2O2 acts as a signal molecule regulating germination in a light-dependent manner. Using photoreceptors null-mutants and GA-deficient mutants, we showed that H2O2-dependent promotion of germination relies on phytochrome signalling, but not on cryptochrome signalling, and that ROS signalling requires GA signalling.
萌发受外部因素的控制，例如温度、水、光和激素平衡。最近，活性氧（ROS）已被证明在植物发育、应激反应和程序性细胞死亡过程中作为信号分子发挥作用。我们分析了 ROS 在萌发过程中的作用，并证明 ROS 除了作为细胞壁疏松因子外，还是该过程中必需的信号分子。事实上，我们表明 ROS 在胚乳破裂之前释放，其产生对于萌发是必需的，并且作为 ROS 水平调节剂的 III 类过氧化物酶与 ROS 产生共定位。在 ROS 中，H2O2 在萌发的早期步骤中修饰了编码调节 ROS 水平的酶的基因的表达。这指出了 ROS 产生的调节反馈回路。GA 和 ABA 应用后内源 ROS 水平的测量表明，ABA 通过抑制 ROS 积累来抑制萌发，而 GA 通过促进 ROS 水平的增加来触发萌发。我们在经过特定 ROS 清除剂处理的拟南芥种子中跟踪了萌发的早期可见步骤（种皮和胚乳破裂），由于光质感知对于正常萌发是必需的，我们研究了在不同光质下外源 H2O2 存在下的萌发情况。H2O2 要么促进萌发，要么抑制萌发，这取决于光波长，表明 H2O2 作为一种信号分子，以依赖于光的方式调节萌发。使用光受体缺失突变体和 GA 缺陷突变体，我们表明 H2O2 依赖的萌发促进依赖于光敏色素信号，但不依赖于隐花色素信号，并且 ROS 信号需要 GA 信号。
