REVIEW: PART OF A SPECIAL ISSUE ON PLANT NUTRITION Nitrogen uptake, assimilation and remobilization in plants: challenges for sustainable and productive agriculture
01 Jan 2010-
TL;DR: In this paper, a review of the physiological, metabolic, and genetic aspects of nitrogen uptake, assimilation, and remobilization in crop plants is presented and the enzymes and regulatory processes manipulated to improve NUE components are also discussed.
Abstract: †Background Productive agriculture needs a large amount of expensive nitrogenous fertilizers. Improving nitrogen use efficiency (NUE) of crop plants is thus of key importance. NUE definitions differ depending on whether plants are cultivated to produce biomass or grain yields. However, for most plant species, NUE mainly depends on how plants extract inorganic nitrogen from the soil, assimilate nitrate and ammonium, and recycle organic nitrogen. Efforts have been made to study the genetic basis as well as the biochemical and enzymatic mechanisms involved in nitrogen uptake, assimilation, and remobilization in crops and model plants. The detection of the limiting factors that could be manipulated to increase NUE is the major goal of such research. †Scope An overall examination of the physiological, metabolic, and genetic aspects of nitrogen uptake, assimilation and remobilization is presented in this review. The enzymes and regulatory processes manipulated to improve NUE components are presented. Results obtained from natural variation and quantitative trait loci studies are also discussed. †Conclusions This review presents the complexity of NUE and supports the idea that the integration of the numerous data coming from transcriptome studies, functional genomics, quantitative genetics, ecophysiology and soil science into explanatory models of whole-plant behaviour will be promising.
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TL;DR: The limiting factors in plant metabolism for maximizing NUE are different at high and low N supplies, indicating great potential for improving the NUE of current cultivars, which were bred in well-fertilized soil.
Abstract: Crop productivity relies heavily on nitrogen (N) fertilization. Production and application of N fertilizers consume huge amounts of energy, and excess is detrimental to the environment; therefore, increasing plant N use efficiency (NUE) is essential for the development of sustainable agriculture. Plant NUE is inherently complex, as each step—including N uptake, translocation, assimilation, and remobilization—is governed by multiple interacting genetic and environmental factors. The limiting factors in plant metabolism for maximizing NUE are different at high and low N supplies, indicating great potential for improving the NUE of current cultivars, which were bred in well-fertilized soil. Decreasing environmental losses and increasing the productivity of crop-acquired N requires the coordination of carbohydrate and N metabolism to give high yields. Increasing both the grain and N harvest index to drive N acquisition and utilization are important approaches for breeding future high-NUE cultivars.
1,382 citations
TL;DR: An introduction to plant mineral nutrition is provided and how mineral elements are taken up by roots and distributed within plants are explained and a perspective on how agriculture can produce edible crops that contribute sufficient mineral elements for adequate animal and human nutrition is concluded.
788 citations
TL;DR: Recent advances in carbon/nitrogen metabolisms as well as sensing and signaling systems in illuminated leaves of C3-plants are discussed and a perspective of the type of experiments that are now required in order to take understanding to a higher level is provided.
581 citations
TL;DR: This review integrates the current knowledge regarding inorganic and organic nitrogen management at the whole-plant level, spanning from nitrogen uptake to remobilization and utilization in source and sink organs, demonstrating that nitrogen transporters are effective targets to improve crop productivity and nitrogen use efficiency.
Abstract: Contents Summary 35 I. Introduction 35 II. Nitrogen acquisition and assimilation 36 III. Root-to-shoot transport of nitrogen 38 IV. Nitrogen storage pools in vegetative tissues 39 V. Nitrogen transport from source leaf to sink 40 VI. Nitrogen import into sinks 42 VII. Relationship between source and sink nitrogen transport processes and metabolism 43 VIII. Regulation of nitrogen transport 43 IX. Strategies for crop improvement 44 X. Conclusions 46 Acknowledgements 47 References 47 SUMMARY: Nitrogen is an essential nutrient for plant growth. World-wide, large quantities of nitrogenous fertilizer are applied to ensure maximum crop productivity. However, nitrogen fertilizer application is expensive and negatively affects the environment, and subsequently human health. A strategy to address this problem is the development of crops that are efficient in acquiring and using nitrogen and that can achieve high seed yields with reduced nitrogen input. This review integrates the current knowledge regarding inorganic and organic nitrogen management at the whole-plant level, spanning from nitrogen uptake to remobilization and utilization in source and sink organs. Plant partitioning and transient storage of inorganic and organic nitrogen forms are evaluated, as is how they affect nitrogen availability, metabolism and mobilization. Essential functions of nitrogen transporters in source and sink organs and their importance in regulating nitrogen movement in support of metabolism, and vegetative and reproductive growth are assessed. Finally, we discuss recent advances in plant engineering, demonstrating that nitrogen transporters are effective targets to improve crop productivity and nitrogen use efficiency. While inorganic and organic nitrogen transporters were examined separately in these studies, they provide valuable clues about how to successfully combine approaches for future crop engineering.
413 citations
TL;DR: Improved understanding of the physiological factors underlying progress in maize yield response to N over time, within the context of changing G × E ×-M factors, serves to help guide maize programs focused on achieving further improvements in N use efficiency.
394 citations
References
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TL;DR: The eFP Browser software is easily adaptable to microarray or other large-scale data sets from any organism and thus should prove useful to a wide community for visualizing and interpreting these data sets for hypothesis generation.
Abstract: Summary In conclusion, the eFP Browser is a convenient tool forinterpreting and visualizing gene expression and other data. Notonly is it valuable for its compatibility to existing resources but ithas also been loaded with several useful data sets. The variousmodes and other features allow the user to extract an array ofconclusions and/or generate useful hypotheses. We hope thatmany researchers will be able to use the eFP Browser both tounderstand particular microarray or other experimental results, aswell as to communicate their own findings. MATERIALS AND METHODS The eFP Browser is implemented in Python and makes use of thePython Imaging Library (PIL) Build 1.1.5 (www.python.org),which we modified to provide an optimized flood pixel re-placement function called replaceFill, and other Python modules,as described on the eFP Browser development homepage. Theinputs for the eFP Browser are illustrated in Figure 1. Apictographic representation of the sample collection as a Targa-based image is required, as is an XML control file, shown in detailin Figure 1B. Two other inputs are a database of gene identifiersand their appropriate microarray element lookups and annota-tions, and a database of gene expression values for the givensamples. In the case of the Arabidopsis, Cell and Mouse eFPBrowsers, we have mirrored publicly-available microarray datafrom several sources – described in the Data Sources andsubsequent two sections – in our Bio-Array Resource [10]. Theseinputs are used by the eFP Browser algorithm to generate anoutput image for a user’s gene identifier.The eFP Browser algorithm itself is programmed in an object-oriented manner. The main program, efpWeb.cgi, is responsiblefor the creation of the HTML code for the user interface andpresentation of the output image. It calls on four modules tocomplete the task. These modules are 1) efp.py, which performsmost of the functions for the generation of the output image,including the parsing of the XML control file, average andstandard deviation calculations, fold-change relative to controlvalue calculations, and image map HTML code; 2) efpDb.py,which connects to the gene expression, microarray element andannotation databases, and returns the appropriate values uponbeing called; 3) efpImg.py, which formulates the actual colourreplace calls on the Targa input image; and 4) efpXML.py, whichidentifies the XML control files that are present in the eFPBrowser’s data directory. These are displayed to the user in theData Source drop-down, thus obviating the need to have themhard-coded in the main efpWeb.cgi program.In the case of the Cell eFP Browser, data in the SUBAdatabase indicate the presence of a given protein in a particularsubcellular location, either based on computational methods or asmolecularly documented by mass spectrometric analysis ofsubcellular fractions, GFP fusions etc. [11]. We have used a simpleheuristic to turn these data into a confidence score for a given geneproduct’s presence in a given subcellular compartment:confidence~X
2,416 citations
01 Jan 1981
TL;DR: Yoshida, Shouichi as discussed by the authors, et al. 1981.Fundamentals of rice crop science, report,Laguna, PhilippinesInternational Rice Research Institute (IRI),
Abstract: Yoshida, Shouichi.1981.Fundamentals of rice crop science,Report,Laguna, PhilippinesInternational Rice Research Institute
1,707 citations
TL;DR: The positional cloning of Gpc-B1, a wheat quantitative trait locus associated with increased grain protein, zinc, and iron content, is reported here, and reduction in RNA levels of the multiple NAM homologs by RNA interference delayed senescence by more than 3 weeks and reduced wheat grain protein and zinc content.
Abstract: Enhancing the nutritional value of food crops is a means of improving human nutrition and health. We report here the positional cloning of Gpc-B1, a wheat quantitative trait locus associated with increased grain protein, zinc, and iron content. The ancestral wild wheat allele encodes a NAC transcription factor (NAM-B1) that accelerates senescence and increases nutrient remobilization from leaves to developing grains, whereas modern wheat varieties carry a nonfunctional NAM-B1 allele. Reduction in RNA levels of the multiple NAM homologs by RNA interference delayed senescence by more than 3 weeks and reduced wheat grain protein, zinc, and iron content by more than 30%.
1,377 citations
TL;DR: These studies uncover surprisingly pivotal roles of KIN10/11 in linking stress, sugar and developmental signals to globally regulate plant metabolism, energy balance, growth and survival.
Abstract: Photosynthetic plants are the principal solar energy converter sustaining life on Earth. Despite its fundamental importance, little is known about how plants sense and adapt to darkness in the daily light-dark cycle, or how they adapt to unpredictable environmental stresses that compromise photosynthesis and respiration and deplete energy supplies. Current models emphasize diverse stress perception and signalling mechanisms. Using a combination of cellular and systems screens, we show here that the evolutionarily conserved Arabidopsis thaliana protein kinases, KIN10 and KIN11 (also known as AKIN10/At3g01090 and AKIN11/At3g29160, respectively), control convergent reprogramming of transcription in response to seemingly unrelated darkness, sugar and stress conditions. Sensing and signalling deprivation of sugar and energy, KIN10 targets a remarkably broad array of genes that orchestrate transcription networks, promote catabolism and suppress anabolism. Specific bZIP transcription factors partially mediate primary KIN10 signalling. Transgenic KIN10 overexpression confers enhanced starvation tolerance and lifespan extension, and alters architecture and developmental transitions. Significantly, double kin10 kin11 deficiency abrogates the transcriptional switch in darkness and stress signalling, and impairs starch mobilization at night and growth. These studies uncover surprisingly pivotal roles of KIN10/11 in linking stress, sugar and developmental signals to globally regulate plant metabolism, energy balance, growth and survival. In contrast to the prevailing view that sucrose activates plant SnRK1s (Snf1-related protein kinases), our functional analyses of Arabidopsis KIN10/11 provide compelling evidence that SnRK1s are inactivated by sugars and share central roles with the orthologous yeast Snf1 and mammalian AMPK in energy signalling.
1,278 citations
TL;DR: Important progress has been made in identifying transport and regulatory mechanisms for macronutrients and the mechanisms of uptake and distribution and the main physiological roles of each nutrient will be discussed.
1,208 citations