Biology Department, Colorado State University, Fort Collins, CO 80523, USA.
Antioxid Redox Signal. 2013 Sep 20;19(9):919-32. doi: 10.1089/ars.2012.5084. Epub 2013 Jan 23.
Photosynthesis, the process that drives life on earth, relies on transition metal (e.g., Fe and Cu) containing proteins that participate in electron transfer in the chloroplast. However, the light reactions also generate high levels of reactive oxygen species (ROS), which makes metal use in plants a challenge.
Sophisticated regulatory networks govern Fe and Cu homeostasis in response to metal ion availability according to cellular needs and priorities. Molecular remodeling in response to Fe or Cu limitation leads to its economy to benefit photosynthesis. Fe toxicity is prevented by ferritin, a chloroplastic Fe-storage protein in plants. Recent studies on ferritin function and regulation revealed the interplay between iron homeostasis and the redox balance in the chloroplast.
Although the connections between metal excess and ROS in the chloroplast are established at the molecular level, the mechanistic details and physiological significance remain to be defined. The causality/effect relationship between transition metals, redox signals, and responses is difficult to establish.
Integrated approaches have led to a comprehensive understanding of Cu homeostasis in plants. However, the biological functions of several major families of Cu proteins remain unclear. The cellular priorities for Fe use under deficiency remain largely to be determined. A number of transcription factors that function to regulate Cu and Fe homeostasis under deficiency have been characterized, but we have not identified regulators that mediate responses to excess. Importantly, details of metal sensing mechanisms and cross talk to ROS-sensing mechanisms are so far poorly documented in plants.
光合作用是地球上生命的驱动力，它依赖于含有过渡金属（如铁和铜）的蛋白质，这些蛋白质参与叶绿体中的电子转移。然而，光反应也会产生高水平的活性氧物种（ROS），这使得植物中的金属利用成为一个挑战。
复杂的调控网络根据细胞的需求和优先级，调控铁和铜的体内平衡，以响应金属离子的可用性。对铁或铜限制的分子重塑导致其经济化，从而有利于光合作用。植物中的叶绿体铁储存蛋白 ferritin 可防止铁毒性。最近关于 ferritin 功能和调控的研究揭示了铁稳态与叶绿体中氧化还原平衡之间的相互作用。
尽管在分子水平上已经确定了叶绿体中金属过量和 ROS 之间的联系，但仍有待定义其机制细节和生理意义。过渡金属、氧化还原信号和反应之间的因果关系/效应关系很难确定。
综合方法已经使人们对植物中的铜体内平衡有了全面的了解。然而，几种主要的 Cu 蛋白家族的生物学功能仍不清楚。在缺乏条件下，Fe 使用的细胞优先级在很大程度上仍有待确定。已经鉴定了许多转录因子，它们在缺乏条件下发挥作用以调节 Cu 和 Fe 体内平衡，但我们尚未鉴定出介导对过量反应的调节剂。重要的是，到目前为止，金属感应机制和与 ROS 感应机制的交叉对话的细节在植物中记录得很差。
