Diaz-Vivancos Pedro, de Simone Ambra, Kiddle Guy, Foyer Christine H
CEBAS-CSIC, Department of Plant Breeding, P.O. Box 164, Campus de Espinardo, 30100 Murcia, Spain.
Centre for Plant Sciences, Faculty of Biology, University of Leeds, Leeds LS2 9JT, UK.
Free Radic Biol Med. 2015 Dec;89:1154-64. doi: 10.1016/j.freeradbiomed.2015.09.023. Epub 2015 Nov 3.
The multifaceted functions of reduced glutathione (gamma-glutamyl-cysteinyl-glycine; GSH) continue to fascinate plants and animal scientists, not least because of the dynamic relationships between GSH and reactive oxygen species (ROS) that underpin reduction/oxidation (redox) regulation and signalling. Here we consider the respective roles of ROS and GSH in the regulation of plant growth, with a particular focus on regulation of the plant cell cycle. Glutathione is discussed not only as a crucial low molecular weight redox buffer that shields nuclear processes against oxidative challenge but also a flexible regulator of genetic and epigenetic functions.
The intracellular compartmentalization of GSH during the cell cycle is remarkably consistent in plants and animals. Moreover, measurements of in vivo glutathione redox potentials reveal that the cellular environment is much more reducing than predicted from GSH/GSSG ratios measured in tissue extracts. The redox potential of the cytosol and nuclei of non-dividing plant cells is about -300 mV. This relatively low redox potential maintained even in cells experiencing oxidative stress by a number of mechanisms including vacuolar sequestration of GSSG. We propose that regulated ROS production linked to glutathione-mediated signalling events are the hallmark of viable cells within a changing and challenging environment.
The concept that the cell cycle in animals is subject to redox controls is well established but little is known about how ROS and GSH regulate this process in plants. However, it is increasingly likely that redox controls exist in plants, although possibly through different pathways. Moreover, redox-regulated proteins that function in cell cycle checkpoints remain to be identified in plants. While GSH-responsive genes have now been identified, the mechanisms that mediate and regulate protein glutathionylation in plants remain poorly defined.
The nuclear GSH pool provides an appropriate redox environment for essential nuclear functions. Future work will focus on how this essential thiol interacts with the nuclear thioredoxin system and nitric oxide to regulate genetic and epigenetic mechanisms. The characterization of redox-regulated cell cycle proteins in plants, and the elucidation of mechanisms that facilitate GSH accumulation in the nucleus are keep steps to unravelling the complexities of nuclear redox controls.
还原型谷胱甘肽（γ-谷氨酰-半胱氨酰-甘氨酸；GSH）的多方面功能一直吸引着植物和动物科学家，尤其是因为GSH与活性氧（ROS）之间的动态关系支撑着还原/氧化（氧化还原）调节和信号传导。在此，我们探讨ROS和GSH在植物生长调节中的各自作用，特别关注植物细胞周期的调节。谷胱甘肽不仅被视为一种关键的低分子量氧化还原缓冲剂，可保护核过程免受氧化挑战，还是遗传和表观遗传功能的灵活调节剂。
在细胞周期中，GSH在植物和动物细胞内的区室化现象非常一致。此外，对体内谷胱甘肽氧化还原电位的测量表明，细胞内环境比从组织提取物中测得的GSH/GSSG比值所预测的要还原得多。未分裂植物细胞的细胞质和细胞核的氧化还原电位约为-300 mV。即使在经历氧化应激的细胞中，通过包括液泡隔离GSSG在内的多种机制，这种相对较低的氧化还原电位仍能维持。我们提出，与谷胱甘肽介导的信号事件相关的ROS产生调控是变化且充满挑战的环境中活细胞的标志。
动物细胞周期受氧化还原控制的概念已得到充分确立，但对于ROS和GSH如何在植物中调节这一过程却知之甚少。然而，越来越有可能的是，植物中存在氧化还原控制，尽管可能通过不同的途径。此外，在植物中仍有待鉴定在细胞周期检查点起作用的氧化还原调节蛋白。虽然现在已经鉴定出了GSH响应基因，但植物中介导和调节蛋白质谷胱甘肽化的机制仍不清楚。
细胞核中的GSH池为基本的核功能提供了合适的氧化还原环境。未来的工作将集中于这种必需的硫醇如何与细胞核硫氧还蛋白系统和一氧化氮相互作用，以调节遗传和表观遗传机制。对植物中氧化还原调节的细胞周期蛋白进行表征，以及阐明促进GSH在细胞核中积累的机制，是解开核氧化还原控制复杂性的重要步骤。
