Elizabeth E. Rogers

Bio: Elizabeth E. Rogers is an academic researcher from University of Missouri. The author has contributed to research in topics: Arabidopsis & Iron deficiency. The author has an hindex of 10, co-authored 17 publications receiving 2586 citations. Previous affiliations of Elizabeth E. Rogers include Dartmouth College.

The FRD3-mediated efflux of citrate into the root vasculature is necessary for efficient iron translocation.

Abstract: Iron, despite being an essential micronutrient, becomes toxic if present at high levels. As a result, plants possess carefully regulated mechanisms to acquire iron from the soil. The ferric reductase defective3 (frd3) mutant of Arabidopsis (Arabidopsis thaliana) is chlorotic and exhibits constitutive expression of its iron uptake responses. Consequently, frd3 mutants overaccumulate iron; yet, paradoxically, the frd3 phenotypes are due to a reduction in the amount of iron present inside frd3 leaf cells. The FRD3 protein belongs to the multidrug and toxin efflux family, members of which are known to export low-Mr organic molecules. We therefore hypothesized that FRD3 loads an iron chelator necessary for the correct distribution of iron throughout the plant into the xylem. One such potential chelator is citrate. Xylem exudate from frd3 plants contains significantly less citrate and iron than the exudate from wild-type plants. Additionally, supplementation of growth media with citrate rescues the frd3 phenotypes. The ectopic expression of FRD3-GFP results in enhanced tolerance to aluminum in Arabidopsis roots, a hallmark of organic acid exudation. Consistent with this result, approximately 3 times more citrate was detected in root exudate from plants ectopically expressing FRD3-GFP. Finally, heterologous studies in Xenopus laevis oocytes reveal that FRD3 mediates the transport of citrate. These results all strongly support the hypothesis that FRD3 effluxes citrate into the root vasculature, a process important for the translocation of iron to the leaves, as well as confirm previous reports suggesting that iron moves through the xylem as a ferric-citrate complex. Our results provide additional answers to long-standing questions about iron chelation in the vasculature and organic acid transport.

Altered selectivity in an Arabidopsis metal transporter.

Abstract: Plants require metals for essential functions ranging from respiration to photosynthesis. These metals also contribute to the nutritional value of plants for both humans and livestock. Additionally, plants have the ability to accumulate nonessential metals such as cadmium and lead, and this ability could be harnessed to remove pollutant metals from the environment. Designing a transporter that specifically accumulates certain cations while excluding others has exciting applications in all of these areas. The Arabidopsis root membrane protein IRT1 is likely to be responsible for uptake of iron from the soil. Like other Fe(II) transporters identified to date, IRT1 transports a variety of other cations, including the essential metals zinc and manganese as well as the toxic metal cadmium. By heterologous expression in yeast, we show here that the replacement of a glutamic acid residue at position 103 in wild-type IRT1 with alanine increases the substrate specificity of the transporter by selectively eliminating its ability to transport zinc. Two other mutations, replacing the aspartic acid residues at either positions 100 or 136 with alanine, also increase IRT1 metal selectivity by eliminating transport of both iron and manganese. A number of other conserved residues in or near transmembrane domains appear to be essential for all transport function. Therefore, this study identifies at least some of the residues important for substrate selection and transport in a protein belonging to the ZIP gene family, a large transporter family found in a wide variety of organisms.

The FRD3-Mediated Efflux of Citrate into the Root Vasculature Is Necessary for Efficient

Abstract: Iron, despite being an essential micronutrient, becomes toxic if present at high levels. As a result, plants possess carefully regulated mechanisms to acquire iron from the soil. The ferric reductase defective3 (frd3) mutant of Arabidopsis (Arabidopsis thaliana) is chlorotic and exhibits constitutive expression of its iron uptake responses. Consequently, frd3 mutants overaccumulate iron; yet, paradoxically, the frd3 phenotypes are due to a reduction in the amount of iron present inside frd3 leaf cells. The FRD3 protein belongs to the multidrug and toxin efflux family, members of which are known to export low-M r organic molecules. We therefore hypothesized that FRD3 loads an iron chelator necessary for the correct distribution of iron throughout the plant into the xylem. One such potential chelator is citrate. Xylem exudate from frd3 plants contains significantly less citrate and iron than the exudate from wild-type plants. Additionally, supplementation of growth media with citrate rescues the frd3 phenotypes. The ectopic expression of FRD3-GFP results in enhanced tolerance to aluminum in Arabidopsis roots, a hallmark of organic acid exudation. Consistent with this result, approximately 3 times more citrate was detected in root exudate from plants ectopically expressing FRD3-GFP. Finally, heterologous studies in Xenopus laevis oocytes reveal that FRD3 mediates the transport of citrate. These results all strongly support the hypothesis that FRD3 effluxes citrate into the root vasculature, a process important for the translocation of iron to the leaves, as well as confirm previous reports suggesting that iron moves through the xylem as a ferric-citrate complex. Our results provide additional answers to longstanding questions about iron chelation in the vasculature and organic acid transport. Plants, like most other organisms, require iron for essential everyday processes. Iron’s usefulness is primarily derived from its ability to adopt two different ionic states; consequently, iron is present in many enzymes that catalyze redox reactions or are involved in electron transfer. Iron is abundant in most soils, yet exists mostly as Fe(III) hydroxides, which are sparingly soluble at neutral pH. Plants use two different strategies to extract iron under these conditions. One approach, called Strategy I and utilized by nongraminaceous species, involves the coordinate up-regulation of three biochemical activities in the roots of irondeficient plants (Marschner, 1995). The rhizosphere is

Genomic scale profiling of nutrient and trace elements in Arabidopsis thaliana

Abstract: Understanding the functional connections between genes, proteins, metabolites and mineral ions is one of biology's greatest challenges in the postgenomic era. We describe here the use of mineral nutrient and trace element profiling as a tool to determine the biological significance of connections between a plant's genome and its elemental profile. Using inductively coupled plasma spectroscopy, we quantified 18 elements, including essential macro- and micronutrients and various nonessential elements, in shoots of 6,000 mutagenized M2 Arabidopsis thaliana plants. We isolated 51 mutants with altered elemental profiles. One mutant contains a deletion in FRD3, a gene known to control iron-deficiency responses in A. thaliana. Based on the frequency of elemental profile mutations, we estimate 2-4% of the A. thaliana genome is involved in regulating the plant's nutrient and trace element content. These results demonstrate the utility of elemental profiling as a useful functional genomics tool.

FRD3, a Member of the Multidrug and Toxin Efflux Family, Controls Iron Deficiency Responses in Arabidopsis

Abstract: We present the cloning and characterization of an Arabidopsis gene, FRD3, involved in iron homeostasis. Plants carrying any of the three alleles of frd3 constitutively express three strategy I iron deficiency responses and misexpress a number of iron deficiency-regulated genes. Mutant plants also accumulate approximately twofold excess iron, fourfold excess manganese, and twofold excess zinc in their shoots. frd3-3 was first identified as man1. The FRD3 gene is expressed at detectable levels in roots but not in shoots and is predicted to encode a membrane protein belonging to the multidrug and toxin efflux family. Other members of this family have been implicated in a variety of processes and are likely to transport small organic molecules. The phenotypes of frd3 mutant plants, which are consistent with a defect in either iron deficiency signaling or iron distribution, indicate that FRD3 is an important component of iron homeostasis in Arabidopsis.

Phosphorus acquisition and use: critical adaptations by plants for securing a nonrenewable resource

Abstract: Contents I. Introduction 424 II. The phosphorus conundrum 424 III. Adaptations to low P 424 IV. Uptake of P 424 V. P deficiency alters root development and function 426 VI. P deficiency modifies carbon metabolism 431 VII. Acid phosphatase 436 VIII. Genetic regulation of P responsive genes 437 IX. Improving P acquisition 439 X. Synopsis 440 Summary Phosphorus (P) is limiting for crop yield on > 30% of the world's arable land and, by some estimates, world resources of inexpensive P may be depleted by 2050. Improvement of P acquisition and use by plants is critical for economic, humanitarian and environmental reasons. Plants have evolved a diverse array of strategies to obtain adequate P under limiting conditions, including modifications to root architecture, carbon metabolism and membrane structure, exudation of low molecular weight organic acids, protons and enzymes, and enhanced expression of the numerous genes involved in low-P adaptation. These adaptations may be less pronounced in mycorrhizal-associated plants. The formation of cluster roots under P-stress by the nonmycorrhizal species white lupin (Lupinus albus), and the accompanying biochemical changes exemplify many of the plant adaptations that enhance P acquisition and use. Physiological, biochemical, and molecular studies of white lupin and other species response to P-deficiency have identified targets that may be useful for plant improvement. Genomic approaches involving identification of expressed sequence tags (ESTs) found under low-P stress may also yield target sites for plant improvement. Interdisciplinary studies uniting plant breeding, biochemistry, soil science, and genetics under the large umbrella of genomics are prerequisite for rapid progress in improving nutrient acquisition and use in plants.

Heavy metals in soils : trace metals and metalloids in soils and their bioavailability

Abstract: Preface.- Contributors.- List of Abbreviations.- Section 1: Basic Principles: Introduction.-Sources of Heavy Metals and Metalloids in Soils.- Chemistry of Heavy Metals and Metalloids in Soils.- Methods for the Determination of Heavy Metals and Metalloids in Soils.- Effects of Heavy Metals and Metalloids on Soil Organisms.- Soil-Plant Relationships of Heavy Metals and Metalloids.- Heavy Metals and Metalloids as Micronutrients for Plants and Animals.-Critical Loads of Heavy Metals for Soils.- Section 2: Key Heavy Metals And Metalloids: Arsenic.- Cadmium.- Chromium and Nickel.- Cobalt and Manganese.- Copper.-Lead.- Mercury.- Selenium.- Zinc.- Section 3: Other Heavy Metals And Metalloids Of Potential Environmental Significance: Antimony.- Barium.- Gold.- Molybdenum.- Silver.- Thallium.- Tin.- Tungsten.- Uranium.- Vanadium.- Glossary of Specialized Terms.- Index.

Biofortification of crops with seven mineral elements often lacking in human diets--iron, zinc, copper, calcium, magnesium, selenium and iodine.

Abstract: Summary The diets of over two-thirds of the world's population lack one or more essential mineral elements. This can be remedied through dietary diversification, mineral supplementation, food fortification, or increasing the concentrations and/or bioavailability of mineral elements in produce (biofortification). This article reviews aspects of soil science, plant physiology and genetics underpinning crop biofortification strategies, as well as agronomic and genetic approaches currently taken to biofortify food crops with the mineral elements most commonly lacking in human diets: iron (Fe), zinc (Zn), copper (Cu), calcium (Ca), magnesium (Mg), iodine (I) and selenium (Se). Two complementary approaches have been successfully adopted to increase the concentrations of bioavailable mineral elements in food crops. First, agronomic approaches optimizing the application of mineral fertilizers and/or improving the solubilization and mobilization of mineral elements in the soil have been implemented. Secondly, crops have been developed with: increased abilities to acquire mineral elements and accumulate them in edible tissues; increased concentrations of ‘promoter’ substances, such as ascorbate, β-carotene and cysteine-rich polypeptides which stimulate the absorption of essential mineral elements by the gut; and reduced concentrations of ‘antinutrients’, such as oxalate, polyphenolics or phytate, which interfere with their absorption. These approaches are addressing mineral malnutrition in humans globally.

IRT1, an Arabidopsis Transporter Essential for Iron Uptake from the Soil and for Plant Growth

Abstract: Plants are the principal source of iron in most diets, yet iron availability often limits plant growth. In response to iron deficiency, Arabidopsis roots induce the expression of the divalent cation transporter IRT1. Here, we present genetic evidence that IRT1 is essential for the uptake of iron from the soil. An Arabidopsis knockout mutant in IRT1 is chlorotic and has a severe growth defect in soil, leading to death. This defect is rescued by the exogenous application of iron. The mutant plants do not take up iron and fail to accumulate other divalent cations in low-iron conditions. IRT1‐green fluorescent protein fusion, transiently expressed in culture cells, localized to the plasma membrane. We also show, through promoter:: � -glucuronidase analysis and in situ hybridization, that IRT1 is expressed in the external cell layers of the root, specifically in response to iron starvation. These results clearly demonstrate that IRT1 is the major transporter responsible for high-affinity metal uptake under iron deficiency.