Regulation of phosphate starvation responses in higher plants.

School of Plant Biology, University of Western Australia, Crawley, WA 6009, Australia.
Annals of Botany (Impact Factor: 3.3). 02/2010; 105(4):513-26. DOI: 10.1093/aob/mcq015
Source: PubMed

ABSTRACT Phosphorus (P) is often a limiting mineral nutrient for plant growth. Many soils worldwide are deficient in soluble inorganic phosphate (P(i)), the form of P most readily absorbed and utilized by plants. A network of elaborate developmental and biochemical adaptations has evolved in plants to enhance P(i) acquisition and avoid starvation.
Controlling the deployment of adaptations used by plants to avoid P(i) starvation requires a sophisticated sensing and regulatory system that can integrate external and internal information regarding P(i) availability. In this review, the current knowledge of the regulatory mechanisms that control P(i) starvation responses and the local and long-distance signals that may trigger P(i) starvation responses are discussed. Uncharacterized mutants that have P(i)-related phenotypes and their potential to give us additional insights into regulatory pathways and P(i) starvation-induced signalling are also highlighted and assessed.
An impressive list of factors that regulate P(i) starvation responses is now available, as is a good deal of knowledge regarding the local and long-distance signals that allow a plant to sense and respond to P(i) availability. However, we are only beginning to understand how these factors and signals are integrated with one another in a regulatory web able to control the range of responses demonstrated by plants grown in low P(i) environments. Much more knowledge is needed in this agronomically important area before real gains can be made in improving P(i) acquisition in crop plants.

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    ABSTRACT: Phosphorus (P) is one of the essential nutrient elements for plant development. In this work, BnPht1;4 gene, encoding a phosphate transporter of PHT1 family, was isolated from Brassica napus. BnPht1;4 possesses the major characteristic of PHT1 high-affinity Pi transporters in plants, such as plasma-membrane localization and 12 transmembrane-spanning domains. Quantitative reverse-transcription PCR analysis and promoter activity assay showed BnPht1;4 was inert in plants under Pi sufficient conditions. However, expression of this gene was remarkably enhanced in roots under Pi deficient conditions. Interestingly, under low Pi conditions, its promoter activity is impaired in tips of elongated roots, suggesting that the high-affinity Pi transporter may be not involved in low Pi response at root tip area. The experimental results also indicated that BnPht1;4 induction by Pi deficiency is dependent on the existence of sugar. In 35S:BnPht1;4 transgenic Arabidopsis, the increase of Pi availability resulted in the change of root architecture under Pi deficient conditions, showing longer primary roots and lower lateral root density than that of wild type. By cis-element analysis, two P1BS and two W-box elements were found in BnPht1;4 promoter. Yeast one-hybrid assay indicated that PHR1 could bind to the BnPht1;4 promoter. P1BS elements in BnPht1;4 promoter are essential for BnPht1;4 induction in Pi starvation response. Furthermore, WRKY75 could bind to the BnPht1;4 promoter, in which W-box elements are important for this binding. These results indicated BnPht1;4 may be dually controlled by two family regulators under low Pi responses. Thus, our data on the regulative mechanism of high-affinity Pi transporter in Pi starvation response will be valuable for B. napus molecular agriculture.
    Plant Molecular Biology 09/2014; 86(6). DOI:10.1007/s11103-014-0249-y · 4.07 Impact Factor
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    ABSTRACT: Preface Phosphorus (P) is an essential, but limiting macronutrient that roots acquire from the soil solution as soluble inorganic phosphate (Pi). The very low concentration of soluble Pi in most unfertilized soils represents a major constraint to plant growth and development. Massive application of Pi-containing fertilizers alleviates soil Pi limitations for plant growth, and has therefore been essential for global food production and security. However, this is a highly-inefficient process as up to 80% of the Pi in applied fertilizers may become insoluble (in previously unfertilized soils), or be incorporated into organic forms (owing to activity of soil microbes), thereby becoming unavailable for uptake by plants that lack specialized adaptations. The use of Pi fertilizers has also had severe ecological consequences in terrestrial freshwater and coastal marine ecosystems, due to Pi runoff from agricultural areas. Moreover, since the P cycle is very slow and the use of Pi fertilizers keeps increasing, world-wide reserves of low-cost non-renewable rock-phosphate needed for production of Pi fertilizers are being depleted. The manufacture, distribution, and application of Pi fertilizers is an energy-intensive process that generates large amounts of ‘greenhouse gas’ emissions. Furthermore, there is scarcity of chemical fertilizers in tropical and subtropical regions where most of the Earth’s population is concentrated. Thus, the field of plant P metabolism continues to be a compelling focus for a broad range of basic and applied research activities in the plant, soil, and environmental sciences. Sustainable management of P in agriculture requires exploitation of P-adaptive traits that will enhance P-acquisition and/or P-use efficiency of crop plants. This goal will be crucial to ensure future agricultural sustainability, sufficient food production for the world’s ever-expanding population, and the overall economic success of agriculture in the 21st century. The advent of genomics, proteomics, and metabolomics has revolutionized the study of plant development, and is also having a significant impact on the study of plant metabolism and its control. Each discovery adds to the view that plant signal transduction and metabolic control networks have remarkable complexity. As discussed throughout this volume, tremendous progress has been made in our understanding of signaling pathways, and related metabolic and physiological mechanisms that underpin plant P-acquisition and P-use efficiency. However, our understanding of P-adaptive traits that allow plants from widely-different environments to acclimate to P-deficiency, within species-dependent limits, is far from complete. The tools needed to address these questions continue to rapidly evolve and hold great promise for those plant molecular geneticists hoping to reap a harvest by engineering crop plants having improved P-efficiency and yield. A volume that reviews this progress while pointing out the major research areas for the future, therefore, is very timely. This volume comprises 14 reviews that bring together the expertise and enthusiasm of an international team of leading authorities. As indicated on the following pages, these reviews provide insights into how plants sense, acquire, recycle, scavenge, and use P, particularly under the naturally-occurring conditions of soluble Pi deficiency that characterize the vast majority of unfertilized soils, world-wide. The chapters are interrelated in order to provide the reader with an integrated view, reviewing information from the current literature and developing novel hypotheses based upon data acquired from extensive and diverse research activities. Following the introductory Chapter 1 of Part I, the six chapters of Part II provide a mechanistic basis of plant P sensing and metabolism. This material will allow a full appreciation of diverse information concerning plant P-starvation responses that are the focus of the five chapters presented in Part III, as well as the role that plant-microbe interactions play in plant P-acquisition that is presented in the two chapters comprising Part IV. William C. Plaxton Hans Lambers
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    ABSTRACT: Pearl millet [Pennisetum glaucum (L.) R. Br] production on the acid sandy Sahelian soils in West Africa (WA) is severely limited bylaw plant-available phosphorus (P) in addition to erratic rainfall. We sought to examine the genetic variability for P uptake and P utilization efficiency in 180 WA pearl millet inbred lines or subsets thereof under low (LP) and high P (HP) conditions in one field and two pot experiments, determine the relationships among the measured traits and grain yield under field conditions at three other independent WA sites, and identify potential secondary selection traits for improving grain yield under LP. We observed genetic variation for P uptake and utilization in both seedling and mature plants. P utilization efficiency increased under LP conditions. Total P uptake was more important for grain production than P utilization under LP field conditions (r = 0.57*** vs r = 0.30***). The estimated response to indirect selection was positive for most of the measured morphological and P-efficiency parameters. We conclude that both seedling and mature plant traits are potentially useful as secondary traits in selection of pearl millet for low-P adaptation. These results should be validated using heterozygous pearl millet genetic materials. Ultimately, pearl millet breeding activities for low P tolerance in WA should be integrated with other system-oriented research such as nutrient cycling, intercropping or rotations with legumes, better crop-tree-livestock integration, and modest applications of locally available rock phosphate.
    02/2015; 171:54-66. DOI:10.1016/j.fcr.2014.11.001