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Query: UMLS:C0240066 (iron deficiency)
 7,156 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Iron is one of the most important micronutrients for plants. Like other organisms, plants have developed active mechanisms for the acquisition of sufficient iron from the soil. Nevertheless, very little is known about the genetic mechanisms that control the active uptake. In tomato, two spontaneously derived mutants are available, which are defective in key steps that control this process. The recessive mutation chloronerva (chln) affects a gene which controls the synthesis of the non-protein amino acid nicotianamine (NA), a key component in the iron physiology of plants. The root system of the recessive mutant fer is unable to induce any of the characteristic responses to iron deficiency and iron uptake is thus completely blocked. We present a characterization of the double mutant, showing that the fer gene is epistatic over the chln gene and thus very likely to be one of the major genetic elements controlling iron physiology in tomato. In order to gain access to these two genes at the molecular level, both mutants were precisely mapped onto the high density RFLP map of tomato. The chln gene is located on chromosome 1 and the fer gene is on chromosome 6 of tomato. Using this high-resolution map, a chromosome walk has been started to isolate the fer gene by map-based cloning. The isolation of the fer gene will provide new insights into the molecular mechanisms of iron uptake control in plants.
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PMID:Genetic analysis of two tomato mutants affected in the regulation of iron metabolism. 880 7

Iron deficiency is among the most common nutritional disorders in plants. To cope with low iron supply, plants with the exception of the Gramineae increase the solubility and uptake of iron by inducing physiological and developmental alterations including iron reduction, soil acidification, Fe(II) transport and root-hair proliferation (strategy I). The chlorotic tomato fer mutant fails to activate the strategy I. It was shown previously that the fer gene is required in the root. Here, we show that fer plants exhibit root developmental phenotypes after low and sufficient iron nutrition indicating that FER acts irrespective of iron supply. Mutant fer roots displayed lower Leirt1 expression than wild-type roots. We isolated the fer gene by map-based cloning and demonstrate that it encodes a protein containing a basic helix-loop-helix domain. fer is expressed in a cell-specific pattern at the root tip independently from iron supply. Our results suggest that FER may control root physiology and development at a transcriptional level in response to iron supply and thus may be the first identified regulator for iron nutrition in plants.
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PMID:The tomato fer gene encoding a bHLH protein controls iron-uptake responses in roots. 1237 Apr 9

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.
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PMID:Differential regulation of nramp and irt metal transporter genes in wild type and iron uptake mutants of tomato. 1270 25

Iron is an essential and commonly limited nutrient for plants. To increase the uptake of iron during times of low iron supply, plants, except the grasses, activate a set of physiological and morphological responses in their roots that include iron reduction, soil acidification, Fe(II) transport and proliferation of root hairs. It is not known how root cells sense and transduce the changes that occur after the onset of iron deficiency. This work presents evidence that nitric oxide (NO) is produced rapidly in the root epidermis of tomato plants (Solanum lycopersicum) that are grown in iron-deficient conditions. The scavenging of NO prevented iron-deficiency-induced upregulation of the basic helix-loop-helix transcription factor FER, the ferric-chelate reductase LeFRO1 and the Fe(II) transporter LeIRT1 genes. On the other hand, exogenous application of the NO donor S-nitrosoglutathione enhanced the accumulation of FER, LeFRO1 and LeIRT1 mRNA in roots of iron-deficient plants. The activity of the root ferric-chelate reductase and the proliferation of root hairs induced by iron deficiency were stimulated by NO supplementation and suppressed by NO scavenging. Nitric oxide was ineffective in inducing iron-deficiency responses in the tomato fer mutant, which indicates that the FER protein is necessary to mediate the action of NO. Furthermore, NO supplementation improved plant growth under low iron supply, which suggests that NO is a key component of the regulatory mechanisms that control iron uptake and homeostasis in plants. In summary, the results of this investigation indicate that an increase in NO production is an early response of roots to iron deprivation that contributes to the improvement of iron availability by (i) modulating the expression of iron uptake-related genes and (ii) regulating the physiological and morphological adaptive responses of roots to iron-deficient conditions.
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PMID:Nitric oxide accumulation is required for molecular and physiological responses to iron deficiency in tomato roots. 1789 45

Plants need to mobilize iron in the soil, and the basic helix-loop-helix transcription factor FER is a central regulator of iron acquisition in tomato roots. FER activity is controlled by iron supply. To analyse to what extent FER influences Fe-regulated protein expression, we investigated the root proteome of wild-type tomato, the fer mutant and a transgenic FER overexpression line under low-iron conditions versus sufficient and generous iron supply. The root proteomes were analysed by two-dimensional gel electrophoresis with three technical and three biological replicates. Statistical analysis identified 39 protein spots that were differentially regulated in selected pairwise comparisons of experimental conditions. Of these, 24 were correlated with expression clusters revealed by principal component analysis. The 39 protein spots were analysed by MALDI-TOF and nanoLC-MS/MS to deduce their possible functions. We investigated the functional representation in the identified expression clusters, and found that loss of FER function in iron-cultured plants mimicked an iron-deficiency status. The largest identified protein expression cluster was upregulated by iron deficiency and in the fer mutant. Two iron-regulated proteins required FER activity for induction by iron deficiency. Few proteins were suppressed by iron deficiency. The differentially expressed proteins belonged predominantly to the functional categories 'stress', 'redox regulation' and 'miscellaneous peroxidases'. Hence, we were able to identify distinct expression clusters of proteins with distinct functions.
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PMID:A proteomic study showing differential regulation of stress, redox regulation and peroxidase proteins by iron supply and the transcription factor FER. 1822 64

To know the root adjustment in response to iron deficiency, differentially displayed proteins in tomato roots of wild type and its iron uptake inefficient mutant T3238fer were analyzed by 2-DE and MALDI-TOF MS-based proteomic method under iron sufficiency and deficiency. Ninety-seven proteins were identified, 63 of them were classified in various metabolic pathways. About 40 proteins involved in starch degradation, TCA and ascorbate cycles were upregulated under iron deficiency and grouped in a network together with glycolysis, whereas proteins for fructose metabolism were decreased. Proteins involved in methionine synthesis, cell wall synthesis, mitochondria ATP synthesis, vacuole ATPase, HSP70/90, etc. also revealed enhanced expression under iron deficiency, while proteins about redox homeostasis, transcription factors, kinases, etc. showed diversified changes. The responses are closely associated with energy metabolism, organic acid formation, root morphological change, redox and sulfur homeostasis, and signal transduction, which enhance iron uptake, reutilization and other adaptive changes. Most of the proteins affected by iron deficiency and fer mutation showed similar effect on individual proteins or pathways, but the independent function of FER to iron deficiency were statistically indicated.
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PMID:Proteomic response to iron deficiency in tomato root. 1845 29