Physiology and toxicology of ion fluxes in plant roots

我的实验室致力于探索植物的运输系统，以及运输途径和植物生产力之间的关系。我在这一领域的许多发现已经被证明是广大科学界的根本兴趣，发表在《自然》、《美国国家科学院院刊》和《植物科学趋势》上，并获得了4300多篇引文。我还通过公开讲座、新闻媒体和个人宣传，特别是通过参与国际水稻研究所等团体以及我自己的倡议--加拿大世界饥饿研究中心，将我的工作奉献给更广大的公众。这些活动和成就，以及其他许多，都是由NSERC始终如一地为我的研究项目提供核心运营资金而成为可能的。 本文提出的研究将促进我们对拟南芥模式植物和农业上重要的谷类植物的根离子运输、矿物质获取和毒性以及植物生长的了解。发现将集中于钾(K)、钠(Na)和铵/氨(NH4/NH3)的运输生理，重点是它们与生长的关系，以及它们之间的相互作用，以及与水和其他土壤离子的相互作用。虽然这是基础科学，但我的研究领域的创新在提高植物生产力方面具有巨大的潜力。 在这些土壤成分中，钾是研究得最好的，但在植物与钾的关系领域，新的前沿有待发现。我们将研究K转运蛋白的全部组成，特别是那些当主要系统在遗传和/或生理上受到损害时运行的转运蛋白。我们还将探索钾营养与NH4/NH3和Na胁迫之间相互作用的鲜为人知的机制，并将研究钾营养与植物水分利用之间的基本联系，特别是在水通道(水通道)活动的背景下。这一领域的发现将有助于解决农业的巨大水足迹问题，特别是世界上最缺水的作物--水稻。 我的实验室长期以来一直专注于植物与氮素的关系，特别是NH4/NH3供应的营养和毒理方面。我们最近已经证明，NH3是毒害下共轭对的主要渗透形式，它进入植物细胞的运输可能是由水通道蛋白介导的。NH_4/NH_3毒性可能与水流直接相关，提示了K缓解NH_4/NH_3毒性的新机制。我们现在正处于一个关键时刻，要找出这种毒性的基本性质，它与NH3的主要运输有关，以及它对其他营养物质和压力的依赖。 我的团队最近在钠转运和毒性领域也取得了实质性进展，从根本上修改了描述这一重要现象的机制模型。钠转运的许多方面仍然知之甚少，钠中毒的确切机制也是如此。有多少钠进入细胞，有多少积累在细胞外？钠靶向细胞扩张、分裂或解体吗？即使在毒性下，细胞内钠的积累也是有益的吗？钠毒害能通过减少根质外体中的溶质流动来改善吗？ 除了在这些关键领域寻求发现之外，我还建议在植物营养学的表观遗传学方面开发一个前沿项目，这方面的知识几乎一无所知。我会问，植物的培育如何影响其后代的水分和养分的利用，以及这种遗传模式如何在分子水平上表现出来。这种营养史前是如何影响植物对矿物质毒害的抵抗力的，这种方法对营养贫瘠或盐碱地的露地种植策略是否有益？

My laboratory is dedicated to the exploration of transport systems in plants, and the relationship between transport pathways and plant productivity. My many discoveries in this area have proven to be of fundamental interest to a broad scientific community, having been published in Nature, PNAS, and Trends in Plant Science, and garnered over 4300 citations. I have also dedicated my work to the greater public, through public lectures, news media and personal outreach, and especially through my involvement with such groups as the International Rice Research Institute, and my own initiative, the Canadian Centre for World Hunger Research. These activities and accomplishments, among many others, have been made possible by the core operating funds consistently provided to my research program by NSERC. The research proposed here will advance our knowledge of root ion transport, mineral acquisition and toxicity, and plant growth, in the Arabidopsis model plant and in agriculturally important cereal grasses. Discovery will focus on the transport physiology of potassium (K+), sodium (Na+), and ammonium/ammonia (NH4+/NH3), with emphasis on their relation to growth, and their interactions with each other, and with water and other soil ions. While this is fundamental science, innovation in my research area has great potential for improvements in plant productivity. Of these soil components, K+ is the best studied, but new frontiers await discovery in the area of plant-K+ relations. We will examine the full complement of K+ transporters, in particular those operating when the main systems are compromised genetically and/or physiologically. We will also explore the poorly understood mechanisms underlying the interactions between K+ nutrition and NH4+/NH3 and Na+ stresses, and we will investigate the fundamental links between K+ nutrition and plant water use, especially in the context of aquaporin (water channel) activity. Discoveries in this area will help address the massive water footprint of agriculture, particularly in rice, the world's thirstiest crop. My laboratory has long specialized in plant-nitrogen relations, particularly nutritional and toxicological aspects of NH4+/NH3 provision. We have recently demonstrated that NH3 is the main permeating form of the conjugate pair under toxicity, and that its transport into plant cells is likely mediated by aquaporins. NH4+/NH3 toxicity may thus be directly tied to water flow, suggesting a new mechanism for its alleviation by K+. We are now at a critical juncture of finding the fundamental nature of this toxicity, in relation to the primary transport of NH3, and its dependence on the presence of other nutrients and stresses. My group has also recently made substantial progress in the area of sodium transport and toxicity, fundamentally revising the mechanistic model describing this important phenomenon. Many aspects of Na+ transport are still poorly understood, as are the exact mechanisms of Na+ toxicity. How much Na+ enters cells, and how much accumulates outside? Does Na+ target cell expansion, division, or disintegration? Can cellular Na+ accumulation be beneficial, even under toxicity? Can Na+ toxicity be ameliorated by reducing solute flow through the root apoplast? In addition to pursuing discovery in these critical areas, I propose to develop a leading-edge program in the epigenetics of plant nutrition, about which virtually nothing is known. I will ask how the rearing of plants influences the water and nutrient use of their descendants, and how such inheritance patterns manifest at a molecular level. How does such nutritional prehistory affect plant resistance to mineral toxicities, and can this approach be beneficial to out-planting strategies in nutrient-poor or saline soils?