Institute of Advanced Research, Gandhinagar, Gujrat, India.
Biotechnology Division, CSIR-Institute of Himalayan Bioresource Technology, Palampur, H.P., India.
Plant Biol (Stuttg). 2021 Sep;23(5):686-694. doi: 10.1111/plb.13260. Epub 2021 May 17.
Reactive oxygen species (ROS) generation within a cell is a natural process of specific subcellular components involved in redox reactions. Within a plant cell, chloroplasts are one of the major sources of ROS generation. Plastid-generated ROS molecules include singlet oxygen ( O ), superoxide radical (O ), hydroxyl radical (OH ) and hydrogen peroxide (H O ), which are produced mainly during photochemical reactions of photosynthesis and chlorophyll biosynthetic process. Under normal growth and developmental, generated ROS molecules act as a secondary messenger controlling several metabolic reactions; however, perturbed environmental conditions lead to multi-fold amplification of cellular ROS that eventually kill the target cell. To maintain homeostasis between production and scavenging of ROS, the cell has instituted several enzymatic and non-enzymatic antioxidant machineries to maintain ROS at a physiological level. Among chloroplastic ROS molecules, excess generation of singlet oxygen ( O ) is highly deleterious to the cell metabolic functions and survival. Interestingly, within cellular antioxidant machinery, enzymes involved in detoxification of O are lacking. Recent studies suggest that under optimal concentrations, O acts as a signalling molecule and drives the cell to either the acclimation pathway or regulated cell death (RCD). Stress-induced RCD is a survival mechanism for the whole plant, while the involvement of chloroplasts and chloroplast-localized molecules that execute RCD are not well understood. In this review, we advocate for participation of chloroplasts-generated O in signalling and RCD in plants.
细胞内活性氧（ROS）的产生是参与氧化还原反应的特定亚细胞成分的自然过程。在植物细胞中，叶绿体是 ROS 产生的主要来源之一。质体产生的 ROS 分子包括单线态氧（1O2）、超氧自由基（O2-）、羟自由基（OH·）和过氧化氢（H2O2），它们主要在光合作用的光化学反应和叶绿素生物合成过程中产生。在正常生长和发育过程中，产生的 ROS 分子作为第二信使，控制着几种代谢反应；然而，环境条件的干扰会导致细胞 ROS 的多倍放大，最终导致靶细胞死亡。为了在 ROS 的产生和清除之间维持平衡，细胞建立了几种酶促和非酶促抗氧化机制，以将 ROS 维持在生理水平。在叶绿体 ROS 分子中，过量产生的单线态氧（1O2）对细胞的代谢功能和生存具有高度的危害性。有趣的是，在细胞抗氧化机制中，缺乏参与 1O2 解毒的酶。最近的研究表明，在最佳浓度下，1O2 作为一种信号分子，促使细胞进入适应途径或调控细胞死亡（RCD）。应激诱导的 RCD 是整个植物的生存机制，而对执行 RCD 的叶绿体和质体定位分子的参与尚不清楚。在这篇综述中，我们提倡叶绿体产生的 1O2 参与植物中的信号转导和 RCD。
