Activation of Rice nicotianamine synthase 2 (OsNAS2) enhances iron availability for biofortification.
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ABSTRACT:
SUBMITTER: Lee S
PROVIDER: S-EPMC3887711 | biostudies-literature | 2012 Mar
REPOSITORIES: biostudies-literature
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Activation of Rice nicotianamine synthase 2 (OsNAS2) enhances iron availability for biofortification.
Lee Sichul S Kim You-Sun YS Jeon Un Sil US Kim Yoon-Keun YK Schjoerring Jan K JK An Gynheung G
Molecules and cells 20120103 3
Because micronutrients in human diets ultimately come from plant sources, malnutrition of essential minerals is a significant public health concern. By increasing the expression of nicotianamine synthase (NAS), we fortified the level of bioavailable iron in rice seeds. Activation of iron deficiency-inducible OsNAS2 resulted in a rise in Fe content (3.0-fold) in mature seeds. Its ectopic expression also increased that content. Enhanced expression led to higher tolerance of Fe deficiency and bette ...[more]
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Project description:The most widespread dietary problem in the world is mineral deficiency. We used the nicotianamine synthase (NAS) gene to increase mineral contents in rice grains. Nicotianamine (NA) is a chelator of metals and a key component of metal homeostasis. We isolated activation-tagged mutant lines in which expression of a rice NAS gene, OsNAS3, was increased by introducing 35S enhancer elements. Shoots and roots of the OsNAS3 activation-tagged plants (OsNAS3-D1) accumulated more Fe and Zn. Seeds from our OsNAS3-D1 plants grown on a paddy field contained elevated amounts of Fe (2.9-fold), Zn (2.2-fold), and Cu (1.7-fold). The NA level was increased 9.6-fold in OsNAS3-D1 seeds. Analysis by size exclusion chromatography coupled with inductively coupled plasma mass spectroscopy showed that WT and OsNAS3-D1 seeds contained equal amounts of Fe bound to IP6, whereas OsNAS3-D1 had 7-fold more Fe bound to a low molecular mass, which was likely NA. Furthermore, this activation led to increased tolerance to Fe and Zn deficiencies and to excess metal (Zn, Cu, and Ni) toxicities. In contrast, disruption of OsNAS3 caused an opposite phenotype. To test the bioavailability of Fe, we fed anemic mice with either engineered or WT seeds for 4 weeks and measured their concentrations of hemoglobin and hematocrit. Mice fed with engineered seeds recovered to normal levels of hemoglobin and hematocrit within 2 weeks, whereas those that ate WT seeds remained anemic. Our results suggest that an increase in bioavailable mineral content in rice grains can be achieved by enhancing NAS expression.
| S-EPMC2799860 | biostudies-literature
Project description:Nearly one-third of the world population, mostly women and children, suffer from iron malnutrition and its consequences, such as anemia or impaired mental development. Biofortification of rice, which is a staple crop for nearly half of the world's population, can significantly contribute in alleviating iron deficiency. NFP rice (transgenic rice expressing nicotianamine synthase, ferritin and phytase genes) has a more than six-fold increase in iron content in polished rice grains, resulting from the synergistic action of nicotianamine synthase (NAS) and ferritin transgenes. We investigated iron homeostasis in NFP plants by analyzing the expression of 28 endogenous rice genes known to be involved in the homeostasis of iron and other metals, in iron-deficient and iron-sufficient conditions. RNA was collected from different tissues (roots, flag leaves, grains) and at three developmental stages during grain filling. NFP plants showed increased sensitivity to iron-deficiency conditions and changes in the expression of endogenous genes involved in nicotianamine (NA) metabolism, in comparison to their non-transgenic siblings (NTS). Elevated transcript levels were detected in NFP plants for several iron transporters. In contrast, expression of OsYSL2, which encodes a member of yellow stripe like protein family, and a transporter of the NA-Fe(II) complex was reduced in NFP plants under low iron conditions, indicating that expression of OsYSL2 is regulated by the endogenous iron status. Expression of the transgenes did not significantly affect overall iron homeostasis in NFP plants, which establishes the engineered push-pull mechanism as a suitable strategy to increase rice endosperm iron content.
| S-EPMC3665926 | biostudies-literature
Project description:Key messageIron and zinc deficiencies negatively impact human health worldwide. We developed wheat lines that meet or exceed recommended dietary target levels for iron and zinc in the grains. These lines represent useful germplasm for breeding new wheat varieties that can reduce iron and zinc deficiency-associated health burdens in the affected populations. Micronutrient deficiencies, including iron and zinc deficiencies, have negative impacts on human health globally. Iron-deficiency; anemia affects nearly two billion people worldwide and is the cause of reduced cognitive development, fatigue and overall low productivity. Similarly, zinc deficiency causes stunted growth, decreased immunity and increased risk of respiratory infections. Biofortification of staple crops is a sustainable and effective approach to reduce the burden of health problems associated with micronutrient deficiencies. Here, we developed wheat lines expressing rice NICOTIANAMINE SYNTHASE 2 (OsNAS2) and bean FERRITIN (PvFERRITIN) as single genes as well as in combination. NAS catalyzes the biosynthesis of nicotianamine (NA), which is a precursor of the iron chelator deoxymugeneic acid (DMA) required for long distance iron translocation. FERRITIN is important for iron storage in plants because it can store up to 4500 iron ions. We obtained significant increases of iron and zinc content in wheat grains of plants expressing either OsNAS2 or PvFERRTIN, or both genes. In particular, wheat lines expressing OsNAS2 greatly surpass the HarvestPlus recommended target level of 30 % dietary estimated average requirement (EAR) for iron, and 40 % of EAR for zinc, with lines containing 93.1 µg/g of iron and 140.6 µg/g of zinc in the grains. These wheat lines with dietary significant levels of iron and zinc represent useful germplasm for breeding new wheat varieties that can reduce micronutrient deficiencies in affected populations.
| S-EPMC5263203 | biostudies-literature
Project description:Iron (Fe) deficiency elevates human mortality rates, especially in developing countries. In Myanmar, the prevalence of Fe-deficient anemia in children and pregnant women are 75 and 71%, respectively. Myanmar people have one of the highest per capita rice consumption rates globally. Consequently, production of Fe-biofortified rice would likely contribute to solving the Fe-deficiency problem in this human population. To produce Fe-biofortified Myanmar rice by transgenic methods, we first analyzed callus induction and regeneration efficiencies in 15 varieties that are presently popular because of their high-yields or high-qualities. Callus formation and regeneration efficiency in each variety was strongly influenced by types of culture media containing a range of 2,4-dichlorophenoxyacetic acid concentrations. The Paw San Yin variety, which has a high-Fe content in polished seeds, performed well in callus induction and regeneration trials. Thus, we transformed this variety using a gene expression cassette that enhanced Fe transport within rice plants through overexpression of the nicotianamine synthase gene HvNAS1, Fe flow to the endosperm through the Fe(II)-nicotianamine transporter gene OsYSL2, and Fe accumulation in endosperm by the Fe storage protein gene SoyferH2. A line with a transgene insertion was successfully obtained. Enhanced expressions of the introduced genes OsYSL2, HvNAS1, and SoyferH2 occurred in immature T2 seeds. The transformants accumulated 3.4-fold higher Fe concentrations, and also 1.3-fold higher zinc concentrations in T2 polished seeds compared to levels in non-transgenic rice. This Fe-biofortified rice has the potential to reduce Fe-deficiency anemia in millions of Myanmar people without changing food habits and without introducing additional costs.
| S-EPMC3664312 | biostudies-literature
Project description:Micronutrient malnutrition is widespread, especially in poor populations across the globe, and iron deficiency anemia is one of the most prevalent forms of micronutrient deficiencies. Iron deficiency anemia has severe consequences for human health, working ability, and quality of life. Several interventions including iron supplementation and food fortification have been attempted and met with varied degrees of success. Rice, which is a staple food for over half of the world's population, is an important target crop for iron biofortification. The genetic variability of iron content in the rice germplasm is very narrow, and thus, conventional breeding has not been successful in developing high iron rice varieties. Therefore, genetic engineering approaches have targeted at increasing iron uptake, translocation, and storage in the rice endosperm. We previously reported that AtIRT1, when expressed together with AtNAS1 and PvFERRITIN (PvFER) in high-iron (NFP) rice, has a synergistic effect of further increasing the iron concentration of polished rice grains. We have now engineered rice expressing AtIRT1, AtNAS1, and PvFER as a single locus gene cassette and compared the resulting lines with transgenic lines expressing AtIRT1 and PvFER gene cassettes. We also evaluated the efficacies of the MsENOD12B and native AtIRT1 promoters for the expression of AtIRT1 in rice in both types of gene cassettes, and found the native AtIRT1 promoter to be a better choice for driving the AtIRT1 expression in our biofortification strategy. All the single insertion transgenic lines have significant increases of iron concentration, both in polished and unpolished grains, but the concerted expression of AtIRT1, AtNAS1, and PvFER resulted to be a more effective strategy in achieving the highest iron increases of up to 10.46 ?g/g dry weight. Furthermore, the transformed high iron lines grew better under iron deficiency growth conditions and also have significantly increased grain zinc concentration. Together, these rice lines have nutritionally relevant increases in polished grain iron and zinc concentration necessary to support human health.
| S-EPMC5293767 | biostudies-literature
Project description:BACKGROUND: Polished rice is a staple food for over 50% of the world's population, but contains little bioavailable iron (Fe) to meet human needs. Thus, biofortifying the rice grain with novel promoters or enhancers of Fe utilization would be one of the most effective strategies to prevent the high prevalence of Fe deficiency and iron deficiency anemia in the developing world. METHODOLOGY/PRINCIPAL FINDINGS: We transformed an elite rice line cultivated in Southern China with the rice nicotianamine synthase gene (OsNAS1) fused to a rice glutelin promoter. Endosperm overexpression of OsNAS1 resulted in a significant increase in nicotianamine (NA) concentrations in both unpolished and polished grain. Bioavailability of Fe from the high NA grain, as measured by ferritin synthesis in an in vitro Caco-2 cell model that simulates the human digestive system, was twice as much as that of the control line. When added at 1:1 molar ratio to ferrous Fe in the cell system, NA was twice as effective when compared to ascorbic acid (one of the most potent known enhancers of Fe bioavailability) in promoting more ferritin synthesis. CONCLUSIONS: Our data demonstrated that NA is a novel and effective promoter of iron utilization. Biofortifying polished rice with this compound has great potential in combating global human iron deficiency in people dependent on rice for their sustenance.
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Project description:To address the problem of iron-deficiency anemia, one of the most prevalent human micronutrient deficiencies globally, iron-biofortified rice was produced using three transgenic approaches: by enhancing iron storage in grains via expression of the iron storage protein ferritin using endosperm-specific promoters, enhancing iron translocation through overproduction of the natural metal chelator nicotianamine, and enhancing iron flux into the endosperm by means of iron(II)-nicotianamine transporter OsYSL2 expression under the control of an endosperm-specific promoter and sucrose transporter promoter. Our results indicate that the iron concentration in greenhouse-grown T(2) polished seeds was sixfold higher and that in paddy field-grown T(3) polished seeds was 4.4-fold higher than that in non-transgenic seeds, with no defect in yield. Moreover, the transgenic seeds accumulated zinc up to 1.6-times in the field. Our results demonstrate that introduction of multiple iron homeostasis genes is more effective for iron biofortification than the single introduction of individual genes.
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Project description:Graminaceous plants release ferric-chelating phytosiderophores that bind to iron. These ferric-phytosiderophore complexes are transported across the plasma membrane by a protein produced from Yellow Stripe 1 (YS1). Here, we report the characterization of OsYSL16, one of the YS1-like genes in rice. Real-time analysis revealed that this gene was constitutively expressed irrespective of metal status. Promoter fusions of OsYSL16 to β-glucuronidase (GUS) showed that OsYSL16 was highly expressed in the vascular tissues of the root, leaf, and spikelet, and in leaf mesophyll cells. The OsYSL16-green fluorescence protein (GFP) fusion protein was localized to the plasma membrane. From a pool of rice T-DNA insertional lines, we identified two independent activation-tagging mutants in OsYSL16. On an Fe-deficient medium, those mutants retained relatively high chlorophyll concentrations compared with the wild-type (WT) controls, indicating that they are more tolerant to a lack of iron. The Fe concentration in shoots was also higher in the OsYSL16 activation lines than in the WT. During germination, the rate of Fe-utilization from the seeds was higher in the OsYSL16 activation lines than in the WT seeds. Our results suggest that the function of OsYSL16 in Fe-homeostasis is to enable distribution of iron within a plant.
| S-EPMC3887722 | biostudies-literature
Project description:Iron (Fe) toxicity in plants causes tissue damage and cellular homeostasis disorders, thereby affecting plant growth and development. Nicotianamine (NA) is a ubiquitous chelator of metal cations and is responsible for metal homeostasis. Rice has three NA synthase (NAS) genes, of which the expression of OsNAS1 and OsNAS2 but not of OsNAS3 is strongly induced in response to Fe deficiency. Recently, we found that OsNAS3 expression is strongly induced with excess Fe in most rice tissues, particularly old leaves, suggesting that it may play a vital role under excess Fe conditions. However, the mechanism by which OsNAS3 responds to excess Fe in rice remains poorly understood. In this study, we clarified the physiological response of OsNAS3 expression to excess Fe and the role of NA synthesis in this condition. Promoter GUS analyses revealed that OsNAS3 was widely expressed in roots, especially in vascular bundle, epidermis, exodermis, stem, and old leaf tissues under Fe excess compared to control plants. Nicotianamine and deoxymugineic acid (DMA; a type of phytosiderophore synthesized by Strategy II species) were present in roots and shoots under Fe excess likewise under control conditions. In addition, OsNAS3 knockout plants were sensitive to excess Fe, exhibiting inferior growth, reduced dry weight, severer leaf bronzing, and greater Fe accumulation in their leaves than non-transformants with excess Fe. We also observed that NA-overproducing rice was tolerant of excess Fe. These results show that NA synthesized by OsNAS3 under Fe excess condition is to mitigate excess Fe whereas NA synthesized by OsNAS1 and OsNAS2 under normal Fe condition is to enhance Fe translocation, suggesting the different roles and functions of the NA existence between these two conditions. Overall, these findings suggest that rice synthesizes NA with OsNAS3 under Fe excess in roots and shoots, and that NA and DMA within the plant body are important for mitigating excess Fe stress and alleviating other metal deficiencies in rice. This report will be important for the development of tolerant rice adapted to Fe-contaminated soils.
| S-EPMC6558524 | biostudies-literature
Project description:In plant cells, a large pool of iron (Fe) is contained in the nucleolus, as well as in chloroplasts and mitochondria. A central determinant for intracellular distribution of Fe is nicotianamine (NA) generated by NICOTIANAMINE SYNTHASE (NAS). Here, we used Arabidopsis thaliana plants with disrupted NAS genes to study the accumulation of nucleolar iron and understand its role in nucleolar functions and more specifically in rRNA gene expression. We found that nas124 triple mutant plants, which contained lower quantities of the iron ligand NA, also contained less iron in the nucleolus. This was concurrent with the expression of normally silenced rRNA genes from nucleolar organizer regions 2 (NOR2). Notably, in nas234 triple mutant plants, which also contained lower quantities of NA, nucleolar iron and rDNA expression were not affected. In contrast, in both nas124 and nas234, specific RNA modifications were differentially regulated in a genotype dependent manner. Taken together, our results highlight the impact of specific NAS activities in RNA gene expression. We discuss the interplay between NA and nucleolar iron with rDNA functional organization and RNA methylation.
| S-EPMC10433931 | biostudies-literature