Iron Deficiency In Plants Research Articles

Exogenous Melatonin Improves Plant Iron Deficiency Tolerance via Increased Accumulation of Polyamine-Mediated Nitric Oxide.

Melatonin has recently been demonstrated to play important roles in the regulation of plant growth, development, and abiotic and biotic stress responses. However, the possible involvement of melatonin in Fe deficiency responses and the underlying mechanisms remained elusive in Arabidopsis thaliana. In this study, Fe deficiency quickly induced melatonin synthesis in Arabidopsis plants. Exogenous melatonin significantly increased the soluble Fe content of shoots and roots, and decreased the levels of root cell wall Fe bound to pectin and hemicellulose, thus alleviating Fe deficiency-induced chlorosis. Intriguingly, melatonin treatments induced a significant increase of nitric oxide (NO) accumulation in roots of Fe-deficient plants, but not in those of polyamine-deficient (adc2-1 and d-arginine-treated) plants. Moreover, the melatonin-alleviated leaf chlorosis was blocked in the polyamine- and NO-deficient (nia1nia2noa1 and c-PTIO-treated) plants, and the melatonin-induced Fe remobilization was largely inhibited. In addition, the expression of some Fe acquisition-related genes, including FIT1, FRO2, and IRT1 were significantly up-regulated by melatonin treatments, whereas the enhanced expression of these genes was obviously suppressed in the polyamine- and NO-deficient plants. Collectively, our results provide evidence to support the view that melatonin can increase the tolerance of plants to Fe deficiency in a process dependent on the polyamine-induced NO production under Fe-deficient conditions.

Further insight into BRUTUS domain composition and functionality

ABSTRACTBRUTUS (BTS) is a hemerythrin (HHE) domain containing E3 ligase that facilitates the degradation of POPEYE-like (PYEL) proteins in a proteasomal-dependent manner. Deletion of BTS HHE domains enhances BTS stability in the presence of iron and also complements loss of BTS function, suggesting that the HHE domains are critical for protein stability but not for enzymatic function. The RING E3 domain plays an essential role in BTS' capacity to both interact with PYEL proteins and to act as an E3 ligase. Here we show that removal of the RING domain does not complement loss of BTS function. We conclude that enzymatic activity of BTS via the RING domain is essential for response to iron deficiency in plants. Further, we analyze possible BTS domain structure evolution and predict that the combination of domains found in BTS is specific to photosynthetic organisms, potentially indicative of a role for BTS and its orthologs in mitigating the iron-related challenges presented by photosynthesis.

From the proteomic point of view: Integration of adaptive changes to iron deficiency in plants

Knowledge about the proteomic adaptations to iron deficiency in plants may contribute to find possible new research targets in order to generate crop plants that are more tolerant to iron deficiency, to increase the iron content or to enhance the bioavailability of iron in food plants. We provide this update on adaptations to iron deficiency from the proteomic standpoint. We have mined the data and compared ten studies on iron deficiency-related proteomic changes in six different Strategy I plant species. We summarize these results and point out common iron deficiency-induced alterations of important biochemical pathways based on the data provided by these publications, deliver explanations on the possible benefits that arise from these adaptations in iron-deficient plants and present a concluding model of these adaptations. Furthermore, we demonstrate the close interdependence of proteins which were found regulated across multiple studies, and we pinpoint proteins with yet unknown function, which may play important roles in iron homeostasis.

Iron deficiency in plants: an insight from proteomic approaches

Iron (Fe) deficiency chlorosis is a major nutritional disorder for crops growing in calcareous soils, and causes decreases in vegetative growth as well as marked yield and quality losses. With the advances in mass spectrometry techniques, a substantial body of knowledge has arisen on the changes in the protein profiles of different plant parts and compartments as a result of Fe deficiency. Changes in the protein profile of thylakoids from several species have been investigated using gel-based two-dimensional electrophoresis approaches, and the same techniques have been used to investigate changes in the root proteome profiles of tomato (Solanum lycopersicum), sugar beet (Beta vulgaris), cucumber (Cucumis sativus), Medicago truncatula and a Prunus rootstock. High throughput proteomic studies have also been published using Fe-deficient Arabidopsis thaliana roots and thylakoids. This review summarizes the major conclusions derived from these “-omic” approaches with respect to metabolic changes occurring with Fe deficiency, and highlights future research directions in this field. A better understanding of the mechanisms involved in root Fe homeostasis from a holistic point of view may strengthen our ability to enhance Fe-deficiency tolerance responses in plants of agronomic interest.

Synthetic Approaches for Iron Type Chelators

Synthetic iron chelators (siderophores mimics) are of paramount interest as clinical iron removal agents (iron overload is one of the most common poisoning) and water-soluble iron complexes can be used to alleviate iron deficiency in plants. Moreover, some additional properties may be needed for a precise function (as examples, probes for studying metal transport, diagnostic tools, agent suited for vectorisation…). We describe in this review the organic syntheses of selected typical examples from our own works. (i) Amphiphilic chelators based on catechol groups. (ii) Mixed ligands based on catechol and quinoline groups. (iii) Quinolobactin, a natural siderophore. (iv) Oxinobactin, a biomimetic synthetic analog of enterobactin involving 8-hydroxyquinoline chelating subunits. Keywords: Siderophore, catechol, 8-hydroxyquinoline, amphiphiles, tripodal scaffolds, Enterobactin

Long-distance signaling of iron deficiency in plants

In a recent issue of the Planta, we established two points regarding the long-distance signal of iron status in tobacco (Nicotiana tabacum L.). One is that the long-distance signal generated in iron deficient tissues is a major factor in positively regulating the expressions of iron uptake genes in tobacco. The expression of a ferric chelate reductase gene (NtFRO1) and an iron-regulated transporter gene (NtIRT1) in roots decreased by cutting off the leaves grown under the iron-deficient condition. Conversely, the leaf-excision did not cause upregulation of the genes under the iron-sufficient condition. These results indicated that signals sent from shoots regulate iron uptake in roots under the iron-deficient condition. The second point regarding the long-distance signals is that the strength of the long-distance signals depends on the size of plant including roots. Both genes expressed in proportion to the weight of the remaining leaves, until a certain threshold. The gene expressions were observed also in hairy roots cultured under the iron deficient condition. In this paper, we discuss the long distance signals of iron status in plants, using a newly obtained data.

Iron and Calcium Availability to Groundnut Plants as Affected by Calcium Carbonate and Water Levels in Calcareous Soil

ABSTRACT To assess possible causes of soil and plant iron deficiency and chlorosis in groundnut (Arachis hypogaea L.) on calcareous clay loam soils of Karnataka, India, a pot experiment was conducted to evaluate the availability of iron and calcium at varying levels of CaCO3 and soil water and their influence on pod yield. The CaCO3 levels of the soil achieved by liming were: 5% (C1), 7% (C2), 10% (C3), 15% (C4), and 20% (C5) (on mass basis). Three soil water levels, i.e., 75% (M1), 150% (M2), and 200% (M3) of field capacity, were imposed for one week each at flowering and pegging stages. Amorphous iron oxide-occluded iron, free iron oxide, and water-soluble calcium increased significantly with increasing levels of soil water. The diethyl triamine pentaacetic acid salt (DTPA)-extractable Fe, however, decreased at higher levels of CaCO3 and soil moisture. Conversely, the concentration of bicarbonate ions increased at higher levels of CaCO3 and soil water. The pod yield of groundnut, which was highest under M2C2, decreased at higher levels of CaCO3. This decrease in groundnut yield at higher levels of CaCO3 was attributed to deficiency of available Fe, DTPA-Fe, as caused by the increased concentration of bicarbonate ions.

The transcription factor IDEF1 regulates the response to and tolerance of iron deficiency in plants

Iron is essential for most living organisms and is often the major limiting nutrient for normal growth. Plants induce iron utilization systems under conditions of low iron availability, but the molecular mechanisms of gene regulation under iron deficiency remain largely unknown. We identified the rice transcription factor IDEF1, which specifically binds the iron deficiency-responsive cis-acting element IDE1. IDEF1 belongs to an uncharacterized branch of the plant-specific transcription factor family ABI3/VP1 and exhibits the sequence recognition property of efficiently binding to the CATGC sequence within IDE1. IDEF1 transcripts are constitutively present in rice roots and leaves. Transgenic tobacco plants expressing IDEF1 under the control of the constitutive cauliflower mosaic virus 35S promoter transactivate IDE1-mediated expression only in iron-deficient roots. Transgenic rice plants expressing an introduced IDEF1 exhibit substantial tolerance to iron deficiency in both hydroponic culture and calcareous soil. IDEF1 overexpression leads to the enhanced expression of the iron deficiency-induced transcription factor gene OsIRO2, suggesting the presence of a sequential gene regulatory network. These findings reveal cis element/trans factor interactions that are functionally linked to the iron deficiency response. Manipulation of IDEF1 also provides another approach for producing crops tolerant of iron deficiency to enhance food and biomass production in calcareous soils.

Abstracts of Nippon Dojo-Hiryogaku Zasshi

Abstracts of Nippon Dojo-Hiryogaku Zasshi

Evaluation of synthetic iron(III)-chelates (EDDHA/Fe 3+, EDDHMA/Fe 3+ and the novel EDDHSA/Fe 3+) to correct iron chlorosis

Soil application of synthetic Fe(III)-chelates, mainly those derived from ethylendiamine di( o-hydroxyphenylacetic) acid (EDDHA) and ethylendiamine di(2-hydroxy-4-methylphenylacetic) acid (EDDHMA), is the most effective, but the most expensive practice used to correct iron deficiency in plants growing on calcareous soils. Previous studies that compared the effectiveness of EDDHA/Fe 3+ and EDDHMA/Fe 3+ always used commercial products and their results are contradictory. In this study, the effectiveness of commercial EDDHA/Fe 3+ and EDDHMA/Fe 3+ fertilizers to correct iron chlorosis in three different crops (sunflower, peach and pear) was compared using doses calculated with the actual content of chelated iron determined by HPLC. The effectiveness of the Fe(III)-chelate derived from the ethylenediamine di(2-hydroxy-5sulfophenylacetic) acid (EDDHSA), that recently has been marketed as iron fertilizer, was also tested in the sunflower and pear experiments. For the three experiments, several parameters related to the plant iron nutritional status, such as leaf growth, yield, SPAD index (chlorophyll concentration), iron content, Fe/Mn ratio and 50(10P+K)/Fe index were determined. Leaf weight, iron concentration per leaf area, leaf iron content, and K/Ca and 50(10P+K)/Fe ratios were well correlated with the degree of chlorosis, suggesting that these parameters could be used for the diagnosis of the plant iron nutritional status when only iron limited the plant growth. One application of the synthetic Fe(III)-chelates (EDDHA/Fe 3+, EDDHMA/Fe 3+ and EDDHSA/Fe 3+) was enough to cause a visible full recovery from iron-deficiency of the three crops. The EDDHSA/Fe 3+ was as effective as the EDDHA/Fe 3+ and EDDHMA/Fe 3+ to correct iron chlorosis in the three different crops, growing either in a soil-less system or in field conditions. However, the doses of EDDHA/Fe 3+ and EDDHMA/Fe 3+ were respectively 1.4- and 1.7-times higher than the EDDHSA/Fe 3+. Although these results pointed out the EDDHSA/Fe 3+ as a promising iron fertilizer, further research is needed to know technical details related to the application such as doses, timing and frequencies as well as its mobility, distribution and persistence in the environment. Soil-less experiments could be a good and quick tool to test the effectiveness of these iron fertilizers, since there were no differences in the order of effectiveness found for the Fe(III)-chelates between soil (field experiments) and soil-less experiments.

Differential Regulation of nramp and irt Metal Transporter Genes in Wild Type and Iron Uptake Mutants of Tomato

Metal transporters regulated by iron can transport a variety of divalent metals, suggesting that iron regulation is important for specificity of iron transport. In plants, the iron-regulated broad-range metal transporter IRT1 is required for uptake of iron into the root epidermis. Functions of other iron-regulated plant metal transporters are not yet established. To deduce novel plant iron transport functions we studied the regulation of four tomato metal transporter genes belonging to the nramp and irt families with respect to environmental and genetic factors influencing iron uptake. We isolated Lenramp1 and Lenramp3 from tomato and demonstrate that these genes encode functional NRAMP metal transporters in yeast, where they were iron-regulated and localized mainly to intracellular vesicles. Lenramp1 and Leirt1 revealed both root-specific expression and up-regulation by iron deficiency, respectively, in contrast to Leirt2 and Lenramp3. Lenramp1 and Leirt1, but not Lenramp3 and Leirt2, were down-regulated in the roots of fer mutant plants deficient in a bHLH gene regulating iron uptake. In chloronerva mutant plants lacking the functional enzyme for synthesis of the plant-specific metal chelator nicotianamine Leirt1 and Lenramp1 were up-regulated despite sufficient iron supply independent of a functional fer gene. Lenramp1 was expressed in the vascular root parenchyma in a similar cellular pattern as the fer gene. However, the fer gene was not sufficient for inducing Lenramp1 and Leirt1 when ectopically expressed. Based on our results, we suggest a novel function for NRAMP1 in mobilizing iron in the vascular parenchyma upon iron deficiency in plants. We discuss fer/nicotianamine synthase-dependent and -independent regulatory pathways for metal transporter gene regulation.

Remedy of chlorosis induced by iron deficiency in plants with the fungal siderophore rhizoferrin

Although microbial siderophores are characterized by high affinity and selectivity for Fe3+, they are usually less efficient as Fe‐carriers to plants than synthetic chelates. An exception to this is rhizoferrin, a fungal siderophore produced by Rhizopus arrhizus isolated and purified by our group. A ferric complex of rhizoferrin was used in this study as an Fe source for tomato and cucumber ("strategy I") and barley and corn ("strategy II") plants grown in nutrient solutions. The Fe‐rhizoferrin complex was found to be an efficient carrier of Fe to these plants. The efficiency of this chelate is comparable with that of the commonly used ferric complexes of ethylenediaminetetraacetic acid (EDTA) and ethylenediamine‐di(o‐hydroxyphenyl)acetic acid (EDDHA). The application of Fe‐rhizoferrin resulted in enhanced plant weight in barley and corn and higher leaf chlorophyll concentration in tomato, barley and com. Iron uptake by Fe‐stressed cucumber plants from the 59Fe chelate of rhizoferrin and other chelators followed the order: EDDHA > rhizoferrin > EDTA > desferrioxamine B (DFOB); 59Fe translocation from roots to shoots followed the order: rhizoferrin = EDDHA > EDTA > DFOB. The high availability of Fe complexed by rhizoferrin for “strategy I” plants is related to its relatively high redox potential and low affinity to Fe2+. The high availability of Fe‐rhizoferrin to “strategy II” plants is related to its relatively low apparent stability constant with Fe3+, which results in the ability of this compound to transfer Fe3+ via ligand exchange to the phytosiderophores which is specifically taken up by the roots.

Effects of cobalt on plants

Effects of cobalt on plants

Ornamental plants most likely to be killed by iron deficiency and some control measures

Abstract A list of over fifty plant species that are commonly used as ornamentals and which are susceptible to iron deficiency, especially in calcareous soils, is given. Although many susceptible plants die of iron deficiency, there are now control measures that will increase survival. Susceptible plants should perhaps be avoided, if possible, on calcareous soils, and the more resistant cultivars may be planted. The next most important control is avoidance of excess soil moisture. Two ways to achieve this are to improve water permeability with polymer soil conditioners and with regulation of irrigation. Soil acidification is helpful, and only part of the soil need be acidified. Elemental sulfur has limited value because it is not readily oxidized by microorganisms in high pH calcareous soils. Iron can be applied to plants by foliar, tree trunk, or root applications, all with varied success. Root application can be preventative and/or corrective. Iron can best be added to roots in zone applications and could include iron salts, iron chelates, natural iron pyrites, waste iron products, or organic matter‐iron mixtures. Avoidance of nutrient imbalances is extremely important in preventing iron deficiency in plants. Proper choice of nitrogen and potassium fertilizer sources can help control iron deficiency.

Substitutes for benzidine as H‐donors in the peroxidase assay, for rapid diagnosis of iron deficiency in plants

Abstract 3,3'5,5’ Tetramethyl benzidine, 3‐Amino‐9‐ethylcarbazol and chlorpromazine are suggested as alternatives for benzidine as H‐donors in the peroxidase assay for diagnosing iron deficiency in plant leaves. Procedures with these reagents, which have been used successfully with citrus and other plants, are described.

Current practices for correcting iron deficiency in plants with emphasis on genetics

Abstract There are important genetic differences in some crop species for the amount of loss in production caused by iron‐deficiency chlorosis. Progress has been made in the correction of iron deficiency by the development and use of iron‐efficient genotypes. Breeders of oat (Avena byzantina C. Koch), dry bean (Phaseolus vulgaris L.), sorghum [Sorghum bicolor (L.) Moench], and soybean [Glycine max (L.) Merrill] are engaged in the selection of cultivars with improved iron efficiency. Genotypes of soybean have been developed with iron efficiency superior to that previously identified in the species. Information on the iron chlorosis resistance of soybean cultivars is provided to farmers to facilitate their selection of appropriate seed. Seed mixtures of efficient and inefficient soybean cultivars are used to maximize production and minimize the risk of crop loss from iron deficiency under appropriate conditions.

Experiments on correcting iron deficiency in plants

Abstract Several approaches to correcting iron deficiency by soil application were studied. Application of chelating agents in simulated drip irrigation, application of sulfuric acid, of organic iron amendments, of crystaline iron ‐ H2SO4 products, and sulfur all have been subjected to experimentation. Most important results include that application via drip irrigation can greatly decrease the quantity of metal chelates needed to correct micronutrient deficiencies, FeDTPA will work on calcareous soils only if the soil is very sandy and if the soil pH is near 7, that zone acidification or zone application of iron amendments in which only part of the root system is adequately supplied with iron will provide a means of both correction of iron deficiency and preventing it for several years in perennial plants, that some H2SO4 to cause soil acidification will increase effectiveness of sulfur as a soil acidifier, that organic‐iron amendments placed in the root zone can provide protection to plants against iron ...

Current management practices for correcting iron deficiency in plants with emphasis on soil management

Abstract Many different kinds of soil additives have been studied with the aim of preventing and/or correcting iron deficiencies of plants. Application rates have varied from as little as “parts per million”; of several Fe chelates, to as much as many tons per hectare of acidifying soil amendments, or organic materials such as manures, sewage sludges and plant residues. The chelate Fe EDDHA has generally been considered to be the most effective soil applied material in alleviating chlorosis: its use is somewhat limited, however, by its relatively high cost. Broadcast applications of acidifying materials such as elemental sulfur and sulfuric acid must generally be excessively high to be effective. Recent studies involving band placements of these acidifying materials have shown some promise. Several industrial by‐products have also proven effective, especially when concentrated in bands close to germinating seeds.

Soil and plant relationships associated with iron deficiency with emphasis on nutrient interactions

Abstract The major cause of iron deficiency in plants is the insolubility of Fe (III) oxides in soils. Minimum solubility occurs in the pH range of 7.4 to 8.5 where the dominant solution species Fe(OH)3° is present at approximately 10‐10.4 M. The critical level of soluble iron for plants is approximately 10‐8 M, so the ferric oxides are too insoluble to supply adequate iron to plants unless modifying factors intervene. Major factors that modify iron solubility relationships in soils include oxidation‐reduction processes and the presence of chelating agents. Reduction processes near respiring plant roots enable ferric chelates to dissociate and Fe3+ to reduce to Fe2+. It is necessary for Fe2+ to increase above the critical level to supply adequate iron to plants. Competition of metal ions for chelating agents gives rise to many nutrient interactions. Redox relationships also affects metal solubility relationships in soils. When combined these factors greatly affect iron availability to plants. Important nu...

Ferrorosamine A fromErwinia rhapontici

The pink pigment ofErwinia rhapontici has been shown to be the known ferrous complex of proferrorosamine A, previously isolated fromPseudomonas species. The identification was based primarily on electronic absorption (visible), mass spectrometric, and nuclear magnetic resonance data. A purification procedure different from those hitherto reported was developed that in the mg range allows the straightforward isolation of both ferrorosamine A and proferrorosamine A as triethylammonium salts suitable for molecular weight determination by field desorption-mass spectrometry.E. rhapontici is pathogenic to various plants and is, therefore, likely to produce one or more unspecific toxic compounds. Proferrorosamine A, the complexation capacity of which can probably cause an iron deficiency in plants, may well be such a factor.