Integrating Cellular Iron Compartmentalization Mechanisms

世界卫生组织（世卫组织）估计，超过20亿人因膳食铁摄入量不足而缺铁。这些人中的大多数主要从植物性饮食中获取铁，而植物性饮食往往具有较低的生物可利用铁水平。此外，世界上约30%的土壤缺铁，导致作物产量大幅下降。铁对于光合作用和呼吸都是必不可少的，然而我们不知道铁是如何被运送到这些重要过程所在的区域的（分别是叶绿体和线粒体）。该项目旨在提供有关铁向这些亚细胞区室输送的基础知识，并使高产、更有营养的作物植物得以发展。该项目将包括在当地公立小学开展外联活动，重点关注植物对人类的重要性以及环境压力因素对植物生长和生产力的影响。铁（Fe）是植物必需的营养物质，在光合作用和呼吸作用的电子传递链中起着重要作用。尽管近年来关于铁从土壤中吸收的机制已经取得了很大进展，但目前对铁的亚细胞运输，特别是线粒体和叶绿体之间的运输，知之甚少。此外，控制细胞器铁稳态和感应的机制仍然未知。该项目建立在PIs之前对铁螯合还原酶（FROs）的研究基础上，这些酶似乎在线粒体和叶绿体铁运输和稳态中起作用，以及线粒体铁转运蛋白（MITs）似乎负责铁进入线粒体的运动。该项目的中心假设是，细胞器上的FROs和mit在铁的区隔化中起关键作用，而铁的区隔化反过来又调节整个植物的铁代谢。在本项目中，将通过分析拟南芥功能缺失系来研究线粒体FROs和MITs的生理作用（Aim 1）。将使用分离和自组装分裂GFP方法来研究细胞器FROs的精确亚细胞器定位和膜拓扑结构（Aim 2）。最后，通过分析叶绿体（fro7）和线粒体（fro3）铁含量降低的系的铁区隔模式和转录谱的变化，研究线粒体和叶绿体对铁的区隔化和铁感知的机制（Aim 3）。因此，该项目将对植物铁转运和积累的分子机制产生重要的新见解。

The World Health Organization (WHO) estimates that more than 2 billion people suffer from iron (Fe) deficiency due to inadequate intake of dietary Fe. The majority of these people obtain their Fe primarily from plant-based diets, which tend to have low levels of bioavailable Fe. In addition, approximately 30% of the world's soils are Fe deficient, resulting in significantly reduced crop yields. Fe is essential for both photosynthesis and respiration, yet we do not know how Fe is delivered to the compartments in which these essential processes are located (chloroplasts and mitochondria, respectively). This project is designed to produce fundamental knowledge concerning the delivery of Fe to these subcellular compartments and enable development of higher-yielding, more nutritious crop plants. This project will include outreach activities in local public primary schools that focus on the importance of plants to humans and the effects of environmental stressors on plant growth and productivity.Iron (Fe) is an essential nutrient for plants where it plays essential roles in the electron transport chains of photosynthesis and respiration. Although much progress has been made in recent years regarding the mechanisms involved in Fe uptake from the soil, current understanding of subcellular trafficking of Fe, particularly trafficking to and from the mitochondria and chloroplasts, is poor. In addition, the mechanisms that control organellar Fe homeostasis and sensing remain unknown. This project builds upon the PIs previous studies of ferric chelate reductases (FROs) that appear to function in mitochondrial and chloroplast Fe trafficking and homeostasis as well as mitochondrial Fe transporters (MITs) that appear to be responsible for movement of Fe into mitochondria. The central hypotheses of the project are that organellar FROs and MITs play critical roles in compartmentalization of Fe, and compartmentalization of Fe, in turn, modulates whole plant Fe metabolism. In this project, the physiological roles of mitochondrial FROs and MITs will be investigated via analysis of Arabidopsis loss-of-function lines (Aim 1). The precise suborganellar localization and membrane topology of organellar FROs will be investigated using fractionation and self-assembling split GFP approaches (Aim 2). Finally, the mechanisms involved in Fe compartmentalization and Fe sensing by mitochondria and chloroplasts will be investigated via analysis of changes in Fe compartmentalization patterns and transcriptional profiles of lines with reduced chloroplast (fro7) and mitochondrial (fro3) Fe content (Aim 3). Thus, this project will generate important new insight into the molecular mechanisms underpinning Fe trafficking and accumulation in plants.