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Jean-François Briat

Bio: Jean-François Briat is an academic researcher from Institut national de la recherche agronomique. The author has contributed to research in topics: Ferritin & Arabidopsis. The author has an hindex of 63, co-authored 137 publications receiving 14082 citations. Previous affiliations of Jean-François Briat include Arts et Métiers ParisTech & University of Montpellier.


Papers
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Journal ArticleDOI
TL;DR: Genetic evidence is presented that IRT1 is essential for the uptake of iron from the soil, and it is shown that I RT1 is expressed in the external cell layers of the root, specifically in response to iron starvation.
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.

1,417 citations

Journal ArticleDOI
18 Jan 2001-Nature
TL;DR: It is shown that ys1 is a membrane protein that mediates iron uptake, and is an important step in understanding iron uptake in grasses, and has implications for mechanisms controlling iron homeostasis in all plants.
Abstract: Frequently, crop plants do not take up adequate amounts of iron from the soil, leading to chlorosis, poor yield and decreased nutritional quality. Extremely limited soil bioavailability of iron has led plants to evolve two distinct uptake strategies: chelation, which is used by the world's principal grain crops1,2; and reduction, which is used by other plant groups3,4,5. The chelation strategy involves extrusion of low-molecular-mass secondary amino acids (mugineic acids) known as ‘phytosiderophores’, which chelate sparingly soluble iron6. The Fe(iii)-phytosiderophore complex is then taken up by an unknown transporter at the root surface7,8. The maize yellow stripe1 (ys1) mutant is deficient in Fe(iii)-phytosiderophore uptake7,8,9,10, therefore YS1 has been suggested to be the Fe(iii)-phytosiderophore transporter. Here we show that ys1 is a membrane protein that mediates iron uptake. Expression of YS1 in a yeast iron uptake mutant restores growth specifically on Fe(iii)-phytosiderophore media. Under iron-deficient conditions, ys1 messenger RNA levels increase in both roots and shoots. Cloning of ys1 is an important step in understanding iron uptake in grasses, and has implications for mechanisms controlling iron homeostasis in all plants.

915 citations

Journal ArticleDOI
TL;DR: The molecular actors involved in iron acquisition from the soil have recently been characterized and a few candidates belonging to various gene families are hypothesized to play major roles in iron distribution throughout the plant.
Abstract: Cellular and whole organism iron homeostasis must be balanced to supply enough iron for metabolism and to avoid excessive, toxic levels. To perform iron uptake from the environment, iron distribution to various organs and tissues, and iron intracellular compartmentalization, various membranes must be crossed by this metal. The uptake and transport of iron under physiological conditions require particular processes such as chelation or reduction because ferric iron has a very low solubility. The molecular actors involved in iron acquisition from the soil have recently been characterized. A few candidates belonging to various gene families are hypothesized to play major roles in iron distribution throughout the plant. All these transport activities are tightly regulated at transcriptional and posttranslational levels, according to the iron status of the plant. These coordinated regulations result from an integration of local and long-distance transduction pathways.

524 citations

Journal ArticleDOI
TL;DR: The sequence of five NRAMP proteins from A. thaliana demonstrate that AtNramp1 participates in the control of iron homoeostasis in plants and leads to an increase in plant resistance to toxic iron concentration.
Abstract: Nramp genes code for a widely distributed class of proteins involved in a variety of processes, ranging from the control of susceptibility to bacterial infection in mammalian cells and taste behaviour in Drosophila to manganese uptake in yeast. Some of the NRAMP proteins in mammals and in yeast are capable of transporting metal ions, including iron. In plants, iron transport was shown to require a reduction/Fe(II) transport system. In Arabidopsis thaliana this process involves the IRT1 and Fro2 genes. Here we report the sequence of five NRAMP proteins from A. thaliana. Sequence comparison suggests that there are two classes of NRAMP proteins in plants: A. thaliana (At) NRAMP1 and Oriza sativa (Os) NRAMP1 and 3 (two rice isologues) represent one class, and AtNRAMP2-5 and OsNRAMP2 the other. AtNramp1 and OsNramp1 are able to complement the fet3fet4 yeast mutant defective both in low- and high-affinity iron transports, whereas AtNramp2 and OsNramp2 fail to do so. In addition, AtNramp1 transcript, but not AtNramp2 transcript, accumulates in response to iron deficiency in roots but not in leaves. Finally, overexpression of AtNramp1 in transgenic A. thaliana plants leads to an increase in plant resistance to toxic iron concentration. Taken together, these results demonstrate that AtNramp1 participates in the control of iron homoeostasis in plants.

499 citations

Journal ArticleDOI
TL;DR: Capillary electrophoresis showed that in the presence of FeII and FeIII, NA preferentially chelates FeII, indicating that the FeIINA complex is kinetically stable under aerobic conditions and suggests that NA will have an important role in scavenging Fe and protecting the cell from oxidative damage.
Abstract: Nicotianamine (NA) occurs in all plants and chelates metal cations, including FeII, but reportedly not FeIII. However, a comparison of the FeII and ZnII affinity constants of NA and various FeIII-chelating aminocarboxylates suggested that NA should chelate FeIII. High-voltage electrophoresis of the FeNA complex formed in the presence of FeIII showed that the complex had a net charge of 0, consistent with the hexadentate chelation of FeIII. Measurement of the affinity constant for FeIII yielded a value of 1020.6, which is greater than that for the association of NA with FeII (1012.8). However, capillary electrophoresis showed that in the presence of FeII and FeIII, NA preferentially chelates FeII, indicating that the FeIINA complex is kinetically stable under aerobic conditions. Furthermore, Fe complexes of NA are relatively poor Fenton reagents, as measured by their ability to mediate H2O2-dependent oxidation of deoxyribose. This suggests that NA will have an important role in scavenging Fe and protecting the cell from oxidative damage. The pH dependence of metal ion chelation by NA and a typical phytosiderophore, 2′-deoxymugineic acid, indicated that although both have the ability to chelate Fe, when both are present, 2′-deoxymugineic acid dominates the chelation process at acidic pH values, whereas NA dominates at alkaline pH values. The consequences for the role of NA in the long-distance transport of metals in the xylem and phloem are discussed.

468 citations


Cited by
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28 Jul 2005
TL;DR: PfPMP1)与感染红细胞、树突状组胞以及胎盘的单个或多个受体作用,在黏附及免疫逃避中起关键的作�ly.
Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1(PfPMP1)与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用,在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员,通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

18,940 citations

Journal ArticleDOI
TL;DR: The mechanisms of ROS generation and removal in plants during development and under biotic and abiotic stress conditions are described and the possible functions and mechanisms for ROS sensing and signaling in plants are compared with those in animals and yeast.
Abstract: Several reactive oxygen species (ROS) are continuously produced in plants as byproducts of aerobic metabolism. Depending on the nature of the ROS species, some are highly toxic and rapidly detoxified by various cellular enzymatic and nonenzymatic mechanisms. Whereas plants are surfeited with mechanisms to combat increased ROS levels during abiotic stress conditions, in other circumstances plants appear to purposefully generate ROS as signaling molecules to control various processes including pathogen defense, programmed cell death, and stomatal behavior. This review describes the mechanisms of ROS generation and removal in plants during development and under biotic and abiotic stress conditions. New insights into the complexity and roles that ROS play in plants have come from genetic analyses of ROS detoxifying and signaling mutants. Considering recent ROS-induced genome-wide expression analyses, the possible functions and mechanisms for ROS sensing and signaling in plants are compared with those in animals and yeast.

9,908 citations

Journal ArticleDOI
14 Jan 2010-Nature
TL;DR: An accurate soybean genome sequence will facilitate the identification of the genetic basis of many soybean traits, and accelerate the creation of improved soybean varieties.
Abstract: Soybean (Glycine max) is one of the most important crop plants for seed protein and oil content, and for its capacity to fix atmospheric nitrogen through symbioses with soil-borne microorganisms. We sequenced the 1.1-gigabase genome by a whole-genome shotgun approach and integrated it with physical and high-density genetic maps to create a chromosome-scale draft sequence assembly. We predict 46,430 protein-coding genes, 70% more than Arabidopsis and similar to the poplar genome which, like soybean, is an ancient polyploid (palaeopolyploid). About 78% of the predicted genes occur in chromosome ends, which comprise less than one-half of the genome but account for nearly all of the genetic recombination. Genome duplications occurred at approximately 59 and 13 million years ago, resulting in a highly duplicated genome with nearly 75% of the genes present in multiple copies. The two duplication events were followed by gene diversification and loss, and numerous chromosome rearrangements. An accurate soybean genome sequence will facilitate the identification of the genetic basis of many soybean traits, and accelerate the creation of improved soybean varieties.

3,743 citations

Journal ArticleDOI
TL;DR: The ways in which plant growth promoting rhizobacteria facilitate the growth of plants are considered and discussed and the possibility of improving plant growth promotion by specific genetic manipulation is critically examined.
Abstract: The ways in which plant growth promoting rhizobacteria facilitate the growth of plants are considered and discussed. Both indirect and direct mechanisms of plant growth promotion are dealt with. Th...

2,529 citations

Journal ArticleDOI
TL;DR: A great deal of research effort is now concentrated on two aspects of ferritin: its functional mechanisms and its regulation and the apparent links between iron and citrate metabolism through a single molecule with dual function are described.

2,486 citations