CAREER: Defining Critical Transport Mechanisms for Chloroplast Osmoregulation and Salt Stress Response

植物是地球上生命的先决条件。通过在叶绿体(一种特殊的细胞室)中进行光合作用，植物将光转化为化学能，并固定大气中的二氧化碳。此外，它们通过释放氧气为我们提供呼吸的空气，它们是我们饮食的主要部分。作为固着的生命形式，植物必须应对不断变化的、往往是恶劣的环境。随着平均气温的上升，干旱和相关的土壤盐分对美国和全球的植物表现和农业生产变得越来越成问题。盐胁迫通过破坏叶绿体微调离子平衡来影响光合作用。这个过程涉及转运蛋白，但大多数编码叶绿体离子转运蛋白的基因都是未知的。昆茨博士和他的团队研究了一组新的植物基因和突变体，以确定它们在叶绿体离子运输中的作用。此外，他的团队正在构建一种基因工具，允许测试所有叶绿体蛋白质和整个蛋白质家族在植物功能和光合作用中的相关性。该工具将被用于精确确定在盐胁迫下对植物表现至关重要的基因。这项研究将为即使在不利的气候条件下提高作物产量提供重要的知识和新的战略。昆茨博士邀请高中生参与他的研究，以提高人们对植物研究及其对可持续未来的重要性的认识，并激发未来一代科学家对世界上最基本的生物化学过程--光合作用的兴趣。植物的光合作用受到土壤盐分的影响，但人们对其中涉及的基因及其提高植物抗性的潜力知之甚少。盐胁迫引起叶绿体核基因和叶绿体蛋白质组转录的变化。生理上，盐胁迫导致叶绿体中有毒的Na+积累和K+的竞争，扰乱叶绿体离子的动态平衡、渗透调节，最终降低光合作用效率。最近，发现了第一个体型K+外排载体。相应的功能丧失突变植物在控制条件下表现出较差的光合作用，但令人惊讶的是，光合作用被盐胁迫所拯救。这强调了在盐胁迫期间，控制质体离子通量以提高光合作用效率的潜力。然而，这一途径受到叶绿体离子转运体数量有限的阻碍，其中最引人注目的是叶绿体K+转运体。一个障碍是叶绿体中基因家族成员的数量太多，这往往导致功能冗余和表型缺乏。本项目将：1.确定胞质K+通道同源物在K+输入中的作用；2.确定与外排突变体意外盐胁迫救援有关的基因。3.构建和应用一个全覆盖的人工文库工具，下调拟南芥所有核编码的叶绿体基因和基因家族的转录，并确定在盐胁迫下与叶绿体Na+内流和低光合作用相关的基因。4.通过在课堂和实验室提供实际操作的分子生物学培训，让高中生参与并激发他们对植物科学和光合作用的兴趣。

Plants are a prerequisite for life on earth. By performing photosynthesis in the chloroplast, a specialized cell compartment, plants transform light into chemical energy and fix CO2 from the atmosphere. Furthermore, they provide the air we breathe by releasing oxygen, and they represent the main part of our diet. As sessile life forms, plants have to cope with constantly changing, often times harsh, environments. As average temperatures rise, drought and interrelated soil salinity become increasingly problematic for plant performance and agricultural production in the US and globally. Salt stress affects photosynthesis by destroying the fine-tuned ion balance in the chloroplast. This process involves transporter proteins but most genes encoding chloroplast ion transporters are unknown. Dr. Kunz and his group investigate a new set of plant genes and mutants to determine their role in chloroplast ion transport. Moreover, his group is building a genetic tool that allows for testing the relevance of all chloroplast proteins and entire protein families in plant function and photosynthesis. The tool will be applied to precisely determine the genes crucial for plant performance under salt stress. This research will provide critical knowledge and new strategies to increase crop yields even under adverse climatic conditions. Dr. Kunz engages high school students in his research to raise awareness for plant research and its significance for a sustainable future and to excite the future generation of scientist for the world's most fundamental biochemical process, photosynthesis.Plant photosynthesis is affected by soil salinity but little is known about the genes involved and their potential to improve plant resistance. Salt stress triggers changes in transcription of nuclear encoded chloroplast genes and the chloroplast proteome. Physiologically, salt stress leads to toxic Na+ accumulation in plastids and outcompeting of K+ which disturbs chloroplast ion homeostasis, osmoregulation, and eventually diminishes photosynthetic efficiency. Recently, the first plastid K+ efflux carriers were discovered. Corresponding loss-of-function mutant plants reveal poor photosynthesis under control conditions but, surprisingly, photosynthesis is rescued by salt stress. This emphasizes the potential of manipulating plastid ion flux to increase photosynthetic efficiency during salt stress. However, this approach is hindered by the limited number of characterized plastid ion transporters, most strikingly a chloroplast K+ importer. One hurdle is the high number of gene family members in chloroplasts which often results in functional redundancy and a lack of phenotypes. This project will: 1. Determine the role of plastid K+ channel homologs for K+ import, 2. Define the genes responsible for the unexpected salt stress rescue of plastid K+ efflux carrier mutants. 3. Build and apply a full-coverage artificial library tool to downregulate all nuclear encoded chloroplast genes and gene family transcripts in Arabidopsis thaliana and determine the genes responsible for plastid Na+ influx and low photosynthesis during salt stress. 4. Engage and excite high school students in plant science and photosynthesis by providing hands-on molecular biology training in the classroom and the laboratory.