Inorganic ions and plant metabolism: targets signals and responses

无机离子和植物代谢：目标信号和响应

基本信息

批准号：
BB/D006775/1
负责人：
Anna Amtmann
金额：
$ 33.38万
依托单位：
University of Glasgow
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2006
资助国家：
英国
起止时间：
2006 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=BB%2FD006775%2F1
关键词：
Inorganic ions plant metabolism targets

项目摘要

A balanced supply of the macronutrients nitrogen, phosphorus and potassium (NPK) to crops is essential for food production but often not achieved in the field. Especially in developing countries K fertilisation has been neglected in favour of N fertilisation, which has led to serious depletion of soils in K. World food production is also threatened by increasing secondary salinisation of agricultural land due to sodium (Na) input through irrigation. Na stress often causes K deficiency as both ions compete for the same transport pathways into and within the plant. K carries out vital functions in growth and metabolism. Sufficient K supply in the field protects crops against herbivore attack, fungal diseases and abiotic stresses (e.g. drought and salinity), and there is evidence that K improves the efficiency of nitrogen usage. Problems related to K deficiency are difficult to spot in the field as visible deficiency symptoms don't appear until very late, at which stage it is often impossible to correct the situation. This is due to the fact that plants efficiently re-distribute K between different tissue and cellular compartments. K homeostasis relies on the ability of the plant to recognise the soil and tissue ion status and to exchange biological signals between cells and tissues. If we can unravel this hidden communication system and identify biological markers of K stress we can develop an early warning system. Thus, knowledge of primary stress targets and signals of K deficiency will be an invaluable help for predicting and treating K related problems in the field. In our laboratory we have recently identified a large set of genes that change their expression in response to the external K supply. Many of the K-regulated genes encode metabolic enzymes, for example those that catalyse reactions in sugar and amino acid metabolism, or sulphur and nitrate assimilation. We also found that the plant hormone jasmonic acid, which is best known for its function in plant defence against insects and fungi, plays a central role in controlling K induced changes in gene expression. These findings relate for the first time plant inorganic ion stress to plant metabolism and pathogen defence at the level of individual genes and signalling compounds. To further characterise K-induced changes in metabolic events we measured levels of amino acids in K starved plants. We observed an increase in glutamine, which explains the previously observed down-regulation of nitrate transporters, which in turn might be the reason for decreased N usage of K deficient crops. An observed decrease in glutamate during K starvation might indicate that the synthesis of this amino acid is impaired and thus the enzyme that catalyses this reaction (GOGAT) might be an early target of K stress. We therefore believe that combined information on K (and Na) stress induced gene expression and metabolite changes can reveal important insights into the interaction between inorganic ions and plant metabolism. The development of novel tools for the standardised analysis of a wide range of metabolites in plant tissues ('metabolomics') allows us to carry out a detailed study of the role of K availability for plant metabolism. In particular, the high sensitivity and the high throughput of metabolomics techniques facilitate a good resolution of metabolite changes in time and space. Such data set will give us for the first time the opportunity to identify metabolic components of mineral deficiency at three distinct levels: (1) primary enzymatic stress targets, (2) metabolic stress signals and (3) adaptive responses involved in re-programming primary and secondary metabolism.

农作物大量营养素氮、磷和钾 (NPK) 的均衡供应对于粮食生产至关重要，但在田间往往无法实现。特别是在发展中国家，钾肥的施肥被忽视，而氮肥的施肥已导致钾肥的土壤严重枯竭。世界粮食生产还受到因灌溉造成的钠（Na）输入导致农田次生盐碱化加剧的威胁。钠胁迫常常导致钾缺乏，因为两种离子竞争进入植物和植物内的相同运输途径。 K 在生长和新陈代谢中发挥重要作用。田间充足的钾供应可以保护作物免受草食动物的攻击、真菌病害和非生物胁迫（例如干旱和盐度），并且有证据表明钾可以提高氮的利用效率。与钾缺乏相关的问题很难在现场发现，因为明显的缺乏症状直到很晚才会出现，在这个阶段通常无法纠正这种情况。这是因为植物在不同的组织和细胞区室之间有效地重新分配钾。 K 稳态依赖于植物识别土壤和组织离子状态以及在细胞和组织之间交换生物信号的能力。如果我们能够解开这个隐藏的通讯系统并识别钾胁迫的生物标记，我们就可以开发一个预警系统。因此，了解主要胁迫目标和缺钾信号对于预测和治疗现场与钾相关的问题将提供宝贵的帮助。在我们的实验室中，我们最近发现了一大组基因，这些基因会根据外部钾供应而改变其表达。许多 K 调节基因编码代谢酶，例如催化糖和氨基酸代谢或硫和硝酸盐同化反应的酶。我们还发现植物激素茉莉酸在控制钾诱导的基因表达变化方面发挥着核心作用，茉莉酸以其在植物防御昆虫和真菌中的功能而闻名。这些发现首次在个体基因和信号化合物水平上将植物无机离子胁迫与植物代谢和病原体防御联系起来。为了进一步表征钾诱导的代谢事件变化，我们测量了缺钾植物中的氨基酸水平。我们观察到谷氨酰胺的增加，这解释了之前观察到的硝酸盐转运蛋白的下调，这反过来可能是缺钾作物氮用量减少的原因。在钾饥饿期间观察到的谷氨酸减少可能表明该氨基酸的合成受到损害，因此催化该反应的酶 (GOGAT) 可能是钾胁迫的早期目标。因此，我们相信，有关钾（和钠）胁迫诱导的基因表达和代谢物变化的综合信息可以揭示无机离子与植物代谢之间相互作用的重要见解。用于对植物组织中多种代谢物进行标准化分析（“代谢组学”）的新工具的开发使我们能够对钾的有效性对植物代谢的作用进行详细研究。特别是代谢组学技术的高灵敏度和高通量有助于很好地解析代谢物在时间和空间上的变化。这样的数据集将使我们第一次有机会在三个不同水平上识别矿物质缺乏的代谢成分：（1）主要酶应激目标，（2）代谢应激信号和（3）参与重新编程初级的适应性反应和次生代谢。