Fe Deficiency Research Articles

In-situ analysis of sub-nanomolar level of Fe(II) in open-ocean waters

Iron (Fe) in seawater is an essential micronutrient for marine phytoplankton, and Fe deficiency limits their growth in high-nutrient, low-chlorophyll areas. The bioavailability of Fe for phytoplankton largely depends on its chemical speciation in seawater. In surface water, the reduction of Fe(III) to Fe(II) is an important step in the uptake of Fe by phytoplankton. However, the marine biogeochemical cycle of Fe(II) in the open ocean has not been fully investigated. In oxic open-ocean waters, Fe(II) is rapidly oxidized and exists at sub-nanomolar levels, making it difficult to determine the Fe(II) concentration of seawater. In this study, we applied the flow analytical method of determining the Fe(II) concentration of seawater using luminol chemiluminescence in an in-situ analyzer (geochemical anomaly monitoring system, GAMOS). In the onboard laboratory, we successfully detected sub-nanomolar levels of Fe(II) in seawater using the GAMOS. In the central Indian Ocean, this analyzer was deployed at a depth of 1000 m to determine the Fe(II) concentration in the water column. During deployment, the detection limit (0.48 nM) was insufficient to determine the concentration. Therefore, we need to lower the blank values and enhance the stability of signal of the in-situ analytical method for application to open-ocean seawater samples.Graphical abstract

Deficiency of Iron in Eucalyptus Plantations of Variable Age in Punjab and its Amelioration

The experiment was conducted during March, 2018 to March, 2020 at Research Farm of Punjab Agricultural University, Ludhiana and a few villages in Ludhiana district of Punjab, India to standardize the application of iron (Fe) in eucalyptus plantations varying from one to five years of age to eradicate Fe deficiency in these plantations. The treatments (g plant-1) consisted of plants without Fe application, 100 g S+100 g FeSO4.7H2O, 200 g S+200 g FeSO4.7H2O, 300 g S+300 g FeSO4.7H2O, 50 g Fe EDTA (iron chelate), 100 g Fe EDTA, 200 g Fe EDTA, 300 g Fe EDTA and 400 g Fe EDTA. The diameter at breast height (DBH) and height of plants were measured at the time of fertilizer application and one year after application. The DBH and height one year after application improved over increase in control by 6.86 and 7.13% respectively in first year plants with 50 g plant-1, 8.58 and 10.16% respectively in second year plants and 9.41 and 10.2% respectively in third year plants with 100 g plant-1, and 10.85 and 11.21% respectively in fourth year plants and 10.27 and 11.87% respectively in fifth year plants with 200 g plant-1 Fe EDTA alongwith correction of Fe deficiency completely. Therefore, the deficiency of Fe can be corrected by application of 50 g plant-1 Fe EDTA to first year plantations, 100 g plant-1 Fe EDTA to second and third year plantations and 200 g plant-1 Fe EDTA to fourth and fifth year plantations of eucalyptus.

Iron (Fe) Nutrient Dynamics in Oil Palm Leaves

Iron (Fe) management is crucial in cultivating oil palm, especially in sandy soils, due to its essential role in supporting photosynthesis and palm metabolism, directly influencing the quality and productivity of oil palms. This study aimed to explore the dynamics of Fe deficiency in oil palm leaves in Central Kalimantan, Indonesia. Using a Split Plot Design, the study compared plant conditions between the control (T0) and three levels of Fe deficiency: low (T1), moderate (T2), and severe (T3). Palm samples were selected using the purposive sampling method. Laboratory analysis of leaf samples indicated a significant decrease in Fe content in deficient palms, with levels of 41.49 µg/g in T1, 42.59 µg/g in T2, and 38.93 µg/g in T3, compared to the control group, which had 67.25 µg/g. The study also revealed that Fe deficiency affects the absorption of other macro and micronutrients. For instance, nitrogen levels increased under moderate Fe deficiency (2.57%), while potassium levels decreased (0.729%) at the same level. Despite the Fe deficiency, the plants adapted by maintaining other nutrient levels within a moderate range. Under severe Fe deficiency conditions, Cu levels reached their highest (5.868 µg/g), while Fe showed a significant decrease. This confirms that oil palm has complex nutrient adaptation and regulation mechanisms to maintain nutrient balance even under deficient conditions. These results emphasize the importance of Fe management in oil palm plantations, especially in sandy soils that are prone to nutrient deficiency.

Valence-state mixing and reduced magnetic moment in Fe3−δGeTe2 single crystals with varying Fe content probed by x-ray spectroscopy

We present a spectroscopic study of the magnetic properties of Fe3−δGeTe2 single crystals with varying Fe content, achieved by tuning the stoichiometry of the crystals. We carried out x-ray absorption spectroscopy and analyzed the x-ray circular magnetic dichroism spectra using the sum rules, to determine the orbital and spin magnetic moments of the materials. We find a clear reduction of the spin and orbital magnetic moment with increasing Fe deficiency. Magnetic susceptibility measurements show that the reduction in magnetization is accompanied by a reduced Curie temperature. Multiplet calculations reveal that the Fe2+ state increasingly mixes with a higher valence state when the Fe deficiency is increased. This effect is correlated with the weakening of the magnetic moment. As single crystals are the base material for exfoliation processes, our results are relevant for the assembly of 2D magnetic heterostructures.

Signaling function of NH4+ in the activation of Fe-deficiency response in cucumber (Cucumis sativus L.).

NH4+ is necessary for full functionality of reduction-based Fe deficiency response in plants. Nitrogen (N) is present in soil mainly as nitrate (NO3-) or ammonium (NH4+). Although the significance of a balanced supply of NO3- and NH4+ for optimal growth has been generally accepted, its importance for iron (Fe) acquisition has not been sufficiently investigated. In this work, hydroponically grown cucumber (Cucumis sativus L. cv. Maximus) plants were supplied with NO3- as the sole N source under -Fe conditions. Upon the appearance of chlorosis, plants were supplemented with 2mM NH4Cl by roots or leaves. The NH4+ treatment increased leaf SPAD and the HCl-extractable Fe concentration while decreased root apoplastic Fe. A concomitant increase in the root concentration of nitric oxide and activity of FRO and its abolishment by an ethylene action inhibitor, indicated activation of the components of Strategy I in NH4+-treated plants. Ammonium-pretreated plants showed higher utilization capacity of sparingly soluble Fe(OH)3 and higher root release of H+, phenolics, and organic acids. The expression of the master regulator of Fe deficiency response (FIT) and its downstream genes (AHA1, FRO2, and IRT1) along with EIN3 and STOP1 was increased by NH4+ application. Temporal analyses and the employment of a split-root system enabled us to suggest that a permanent presence of NH4+ at concentrations lower than 2mM is adequate to produce an unknown signal and causes a sustained upregulation of Fe deficiency-related genes, thus augmenting the Fe-acquisition machinery. The results indicate that NH4+ appears to be a widespread and previously underappreciated component of plant reduction-based Fe deficiency response.

Transcriptomics Provide Insights into Early Responses to Sucrose Signaling in Lupinus albus, a Model Plant for Adaptations to Phosphorus and Iron Deficiency.

Phosphorus (P) and iron (Fe) deficiency are major limiting factors for plant productivity worldwide. White lupin (Lupinus albus L.) has become a model plant for understanding plant adaptations to P and Fe deficiency, because of its ability to form cluster roots, bottle-brush-like root structures play an important role in the uptake of P and Fe from soil. However, little is known about the signaling pathways involved in sensing and responding to P and Fe deficiency. Sucrose, sent in increased concentrations from the shoot to the root, has been identified as a long-distance signal of both P and Fe deficiency. To unravel the responses to sucrose as a signal, we performed Oxford Nanopore cDNA sequencing of white lupin roots treated with sucrose for 10, 15, or 20 min compared to untreated controls. We identified a set of 17 genes, including 2 bHLH transcription factors, that were up-regulated at all three time points of sucrose treatment. GO (gene ontology) analysis revealed enrichment of auxin and gibberellin responses as early as 10 min after sucrose addition, as well as the emerging of ethylene responses at 20 min of sucrose treatment, indicating a sequential involvement of these hormones in plant responses to sucrose.

Iron Metabolism, Calcium, Magnesium and Trace Elements: A Review.

Iron (Fe) is fundamental to life on earth. In the human body, it is both essential and harmful if above threshold. A similar balance applies to other elements: calcium (Ca), magnesium (Mg), and trace elements including copper (Cu), zinc (Zn), lead (Pb), cadmium (Cd), mercury (Hg), and nickel (Ni). These elements share some proteins involved in the absorption and transport of Fe. Cu and Cd can inhibit Fe absorption, while excess of Fe may antagonize Cu metabolism and reduce ceruloplasmin (Cp). Excessive Fe can hinder Zn absorption and transferrin (Trf) can bind to both Zn and Ni. Ca is able to inhibit the divalent metal transporter 1 (DMT1) in a dose-dependent manner to reduce Fe absorption and low Mg concentrations can exacerbate Fe deficiency. Pb competitively inhibits Fe distribution and elevated Cd absorption reduces Fe uptake. Exposure to Hg is associated with higher ferritin concentrations and Ni alters intracellular Fe metabolism. Fe removal by phlebotomy in hemochromatosis patients has shown to increase the levels of Cd and Pb and alter the concentrations of trace elements in some types of anemia. Yet, the effects of chronic exposure of most trace elements remain poorly understood.

A global transcriptional activator involved in the iron homeostasis in cyanobacteria.

Cyanobacteria use a series of adaptation strategies and a complicated regulatory network to maintain intracellular iron (Fe) homeostasis. Here, a global activator named IutR has been identified through three-dimensional chromosome organization and transcriptome analysis in a model cyanobacterium Synechocystis sp. PCC 6803. Inactivation of all three homologous IutR-encoding genes resulted in an impaired tolerance of Synechocystis to Fe deficiency and loss of the responses of Fe uptake-related genes to Fe-deplete conditions. Protein-promoter interaction assays confirmed the direct binding of IutR with the promoters of genes related to Fe uptake, and chromatin immunoprecipitation sequencing analysis further revealed that in addition to Fe uptake, IutR could regulate many other physiological processes involved in intracellular Fe homeostasis. These results proved that IutR is an important transcriptional activator, which is essential for cyanobacteria to induce Fe-deficiency response genes. This study provides in-depth insights into the complicated Fe-deficient signaling network and the molecular mechanism of cyanobacteria adaptation to Fe-deficient environments.

Epigenetic insights into an epimutant colorless non-ripening: from fruit ripening to stress responses.

The epigenetic machinery has received extensive attention due to its involvement in plant growth, development, and adaptation to environmental changes. Recent studies often highlight the epigenetic regulatory network by discussing various epigenetic mutants across various plant species. However, a systemic understanding of essential epigenetic regulatory mechanisms remains limited due to a lack of representative mutants involved in multiple biological processes. Colorless Non-ripening (Cnr), a spontaneous epimutant isolated from a commercial population, was initially characterized for its role in fruit ripening regulation. Cnr fruits exhibit an immature phenotype with yellow skin, attributed to hypermethylation of the SQUAMOSA PROMOTER BINDING PROTEIN-LIKE-CNR (SlSPL-CNR) promoter, resulting in the repression of gene expression. In addition to DNA methylation, this process also involves histone modification and microRNA, integrating multiple epigenetic regulatory factors. Interestingly, knockout mutants of SlSPL-CNR display phenotypical distinctions from Cnr in fruit ripening, indicating complex genetic and epigenetic control over the non-ripening phenotype in Cnr fruits. Accumulating evidence suggests that Cnr epimutation is pleiotropic, participating in various biological processes such as Cd stress, Fe deficiency, vivipary, and cell death. Therefore, the Cnr epimutant serve as an excellent model for unveiling how epigenetic mechanisms are involved in diverse biological processes. This review paper focuses on recent research advances regarding the Cnr epimutant, delving into its complex genetic and epigenetic regulatory mechanisms, with the aim of enhancing our understanding and facilitating the development of high-quality, high-yield crops through epigenetic modification.

Iron biofortification in cereal crops: Recent progress and prospects

AbstractMicronutrient malnutrition is one of the major causes of human disorders in the developing world. Iron (Fe) is an important micronutrient due to its use in human metabolism such as immune system and energy production. Estimates indicate that above 30% of the global population is at risk of Fe deficiency, posing a particular threat to infants and pregnant women. Plants have adapted various strategies for uptake, transport, accumulation, and storage of Fe in tissues and organs which later can be consumed by humans. Biofortification refers to increase in micronutrient concentration in edible parts of plants and understanding the pathways for Fe accumulation in plants. Conventional plant breeding, transgenics, agronomic interventions, and microbe‐mediated biofortification are all potential methods to address Fe deficiency. This review article critically evaluates key aspects pertaining to Fe biofortification in cereal crops. It encompasses an in‐depth analysis of the holistic presence of Fe, its significance in both human and plant contexts, and the diverse strategies employed in Fe uptake, transport, accumulation, and storage in plant parts destined for human consumption. Additionally, the article explores the bioavailability of Fe and investigates strategies for biofortification, with a specific emphasis on both traditional methods and recent breakthroughs aimed at enhancing the Fe content in food crops. Keeping in view the significance of Fe for human life, appropriate biofortification strategies may serve better to eliminate hidden hunger rather than its artificial supplementation.

Estimation of calories intake, iron, zinc, and selenium among children of the underprivileged area in Sindh, Pakistan.

Malnutrition is one of the most serious community health issues in developing countries. This study estimated total energy intake, Iron (Fe), Zinc (Zn), Selenium (Se), Calcium (Ca), and Phosphate (PO4) levels among school-going children (aged 13-17 years) of the underprivileged area in Sindh, Pakistan. Children from Mithi City, District Tharparkar, were selected for this cross-sectional investigation. Students from various schools from both genders who fulfilled the selection criteria were selected. A questionnaire was filled, and five ml blood samples were taken to analyze blood parameters. Each participant's estimated nutrient intake (ENI) per day was assessed and matched to the recommended daily allowance (RDA) to determine their micro and macronutrient intake. A total of 300 school-going children [150(50%) boys (mean age 15± 0.8 years) and 150(50%) girls (mean age 14±1.3years)] were included in this study. Total calories (1449±949 Kcal vs. 1245±215 Kcal; p < .001), carbohydrates (138±27 gm vs. 126 ±25 gm; p < .001) protein (47±9.1 gm vs. 44±6 gm; p < .001) was significantly higher among boys compared to girls. In contrast, calcium (1094±105 mg vs. 1144±100; 0.004), phosphate 1050±125 vs. 1148±147; p<0.001), iron (9.2±1.7 mg vs. 10±1.3 mg; p<0.001), and Zinc (7.4±1.8 mg vs. 9.9±1.7 mg; p<0.001) intake was significantly higher among girls than boys. Gender-wise comparison of serum metals in school-going children showed that serum iron was significantly lower among girls than boys (100.86±25.65 μg/dl vs. 78.48±28.66 μg/dl; p<0.001), and no difference was found in serum Zn, Se, and Ca levels. Total proteins were also significantly lower among girls than boys (6.48±1.01g/dl vs. 4.87±1.4301g/dl; p<0.001). Serum iron, Ca, and total proteins were significantly lower among girls with normal ranges compared to boys with normal ranges. Total protein was significantly lower among girls below normal ranges than boys with normal ranges (p < .001). The correlation of carbohydrates, protein, and fat with some serum biochemical parameters in school-going children showed that serum Fe was significantly linked with proteins (r = 0.255; p < .0.05). Our findings showed a concurrent shortage of macro and micronutrients. The current study also revealed that total energy intake was lower than the RDA and significant Fe, Zn, and Se deficiencies. The findings highlight the importance of measures aimed at improving children's nutritional status.

Iron Chelation in Soil: Scalable Biotechnology for Accelerating Carbon Dioxide Removal by Enhanced Rock Weathering.

Enhanced rock weathering (EW) is an emerging atmospheric carbon dioxide removal (CDR) strategy being scaled up by the commercial sector. Here, we combine multiomics analyses of belowground microbiomes, laboratory-based dissolution studies, and incubation investigations of soils from field EW trials to build the case for manipulating iron chelators in soil to increase EW efficiency and lower costs. Microbial siderophores are high-affinity, highly selective iron (Fe) chelators that enhance the uptake of Fe from soil minerals into cells. Applying RNA-seq metatranscriptomics and shotgun metagenomics to soils and basalt grains from EW field trials revealed that microbial communities on basalt grains significantly upregulate siderophore biosynthesis gene expression relative to microbiomes of the surrounding soil. Separate in vitro laboratory incubation studies showed that micromolar solutions of siderophores and high-affinity synthetic chelator (ethylenediamine-N,N'-bis-2-hydroxyphenylacetic acid, EDDHA) accelerate EW to increase CDR rates. Building on these findings, we develop a potential biotechnology pathway for accelerating EW using the synthetic Fe-chelator EDDHA that is commonly used in agronomy to alleviate the Fe deficiency in high pH soils. Incubation of EW field trial soils with potassium-EDDHA solutions increased potential CDR rates by up to 2.5-fold by promoting the abiotic dissolution of basalt and upregulating microbial siderophore production to further accelerate weathering reactions. Moreover, EDDHA may alleviate potential Fe limitation of crops due to rising soil pH with EW over time. Initial cost-benefit analysis suggests potassium-EDDHA could lower EW-CDR costs by up to U.S. $77 t CO2 ha-1 to improve EW's competitiveness relative to other CDR strategies.

PbbHLH155 enhances iron deficiency tolerance in pear by directly activating PbFRO2 and PbbHLH38

Iron (Fe) deficiency is a general stress for many horticulture crops, causing leaf chlorosis and stunted growth. The basic–helix–loop–helix (bHLH) transcription factor (TF) was reported to function in Fe absorption; however, the regulatory mechanism of bHLH genes on iron absorption remains largely unclear in pear. In this study, we found that PbbHLH155 was significantly induced by Fe deficiency. Overexpression of PbbHLH155 in Arabidopsis thaliana and pear calli significantly increases resistance to Fe deficiency. The PbbHLH155-overexpressed Arabidopsis lines exhibited greener leaf color, higher Fe content, stronger Fe chelate reductase (FCR) and root acidification activity. The PbbHLH155 knockout pear calli showed lower Fe content and weaker FCR activity. Interestingly, PbbHLH155 inhibited the expressions of PbFRO2 and PbbHLH38, which were positive regulators in Fe-deficiency responses (FDR). Furthermore, yeast one-hybrid (Y1H) and Dual-Luciferase Reporter (DLR) assays revealed that PbbHLH155 directly binds to the promoters of PbFRO2 and PbbHLH38, thus activating their expression. Overall, our results showed that PbbHLH155 directly promote the expression of PbFRO2 and PbbHLH38 to activate FCR activity for iron absorption. This study provided valuable information for pear breeding.

The Effects of Exogenous Iron on the Photosynthetic Performance and Transcriptome of Rice under Salt–Alkali Stress

Saline-sodic stress induces iron deficiency in rice, reduces leaf photosynthetic performance, and inhibits yield enhancement. In this study, we investigated the effects of exogenous Fe on the photosynthetic performance and transcriptomics of two different tolerant rice cultivars CB9 (Changbai9: saline tolerant cultivar) and TH899 (Tonghe899: saline sensitive cultivar) with 4-week-old Fe-deficient rice seedlings under saline stress, Fe deficiency stress, and both co-stresses. The results showed that under saline and alkaline stress, spraying exogenous iron favored the growth of the two cultivars of rice, with a 32.68% and 39.82 increase in fresh weight, a 2.20-fold and 2.16-fold increase in pigment, respectively, and an 80.28% and 100.00% increase in net photosynthetic rate, respectively, as compared with the iron-deficiency treatment. Transcriptome analysis showed that we found a higher number of differentially expressed genes (7785 differentially expressed genes) in response to exogenous Fe spraying in the soda-salt sensitive variety TH899. The differentially expressed genes that are common to the two cultivars are primarily enriched in metabolic pathways, including plant hormone signal transduction (map04075) and phenylpropanoid biosynthesis (map00940). Specifically, among these genes, 14 are differentially expressed in the carotenoid biosynthetic metabolic pathway. The differentially expressed genes specific to the salinity-tolerant variety CB9 were mainly enriched in the metabolic pathways of glyoxylate and dicarboxylic acid methyl metabolism (map00630), and carbon fixation in photosynthetic organisms (map00710), among which 20 genes were significantly expressed in the pathway for carbon fixation in photosynthetic organisms (map00710). The research results offer specific theoretical support for enhancing the salt tolerance of rice.

Exploring glycine root uptake dynamics in phosphorus and iron deficient tomato plants during the initial stages of plant development

BackgroundPhosphorus (P) and iron (Fe) deficiencies are relevant plants nutritional disorders, prompting responses such as increased root exudation to aid nutrient uptake, albeit at an energy cost. Reacquiring and reusing exudates could represent an efficient energy and nitrogen saving strategy. Hence, we investigated the impact of plant development, Fe and P deficiencies on this process.Tomato seedlings were grown hydroponically for 3 weeks in Control, -Fe, and -P conditions and sampled twice a week. We used Isotope Ratio Mass-Spectrometry to measure δ13C in roots and shoots after a 2-h exposure to 13C-labeled glycine (0, 50, or 500 μmol L−1). Plant physiology was assessed with an InfraRed Gas Analyzer and ionome with an Inductively Coupled Plasma Mass-Spectrometry.ResultsGlycine uptake varied with concentration, suggesting an involvement of root transporters with different substrate affinities. The uptake decreased over time, with -Fe and -P showing significantly higher values as compared to the Control. This highlights its importance during germination and in nutrient-deficient plants. Translocation to shoots declined over time in -P and Control but increased in -Fe plants, suggesting a role of Gly in the Fe xylem transport.ConclusionsRoot exudates, i.e. glycine, acquisition and their subsequent shoot translocation depend on Fe and P deficiency. The present findings highlight the importance of this adaptation to nutrient deficiencies, that can potentially enhance plants fitness. A thorough comprehension of this trait holds potential significance for selecting cultivars that can better withstand abiotic stresses.

Carbon-based nanomaterials cause toxicity by oxidative stress to the liver and brain in Sprague–Dawley rats

Carbon-based nanomaterials have important research significance in various disciplines, such as composite materials, nanoelectronic devices, biosensors, biological imaging, and drug delivery. Recently, the human and ecological risks associated with carbon-based nanomaterials have received increasing attention. However, the biological safety of carbon based nanomaterials has not been systematically studied. In this study, we used different types of carbon materials, namely, graphene oxide (GO), single-walled carbon nanotubes (SWCNTs), and multiwalled carbon nanotubes (MWCNTs), as models to observe their distribution and oxidative damage in vivo. The results of Histopathological and ultrastructural examinations indicated that the liver and lungs were the main accumulation targets of these nanomaterials. SR-μ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\upmu$$\\end{document}-XRF analysis revealed that SWCNTs and MWCNTs might be present in the brain. This shows that the three types of carbon-based nanomaterials could cross the gas–blood barrier and eventually reach the liver tissue. In addition, SWCNTs and MWCNTs could cross the blood–brain barrier and accumulate in the cerebral cortex. The increase in ROS and MDA levels and the decrease in GSH, SOD, and CAT levels indicated that the three types of nanomaterials might cause oxidative stress in the liver. This suggests that direct instillation of these carbon-based nanomaterials into rats could induce ROS generation. In addition, iron (Fe) contaminants in these nanomaterials were a definite source of free radicals. However, these nanomaterials did not cause obvious damage to the rat brain tissue. The deposition of selenoprotein in the rat brain was found to be related to oxidative stress and Fe deficiency. This information may support the development of secure and reasonable applications of the studied carbon-based nanomaterials.

An iron-deficiency tolerant genotype of sorghum effectively localizes iron to the thylakoid membranes of the bundle sheath cells

ABSTRACT Although sorghum (Sorghum bicolor L.), a C4 grass plant, requires a higher iron (Fe) concentration in its leaves for sufficient growth compared to C3 grass plants, there are differences in Fe-deficiency tolerance among sorghum genotypes. C4 plant sorghum localizes Fe in bundle sheath (BS) cells as a major site for CO2 assimilation; however, the response of chloroplasts in BS cells to Fe deficiency remains unknown. We compared the allocation of Fe and proteins involved in the photosystems between Fe-deficiency-tolerant and Fe-deficiency-susceptible sorghum genotypes. The distribution patterns of the Fe-requiring core proteins of photosystems I and II were the same in both genotypes, whereas the tolerant genotype, line D100, allocated more Fe to the BS thylakoid membranes than the susceptible genotype, regardless of Fe nutritional status and leaf Fe content. These results suggest that the tolerant D100 sorghum line has mechanisms to supply sufficient Fe to the BS thylakoid membranes.

Exploring the Role of Debaryomyces hansenii as Biofertilizer in Iron-Deficient Environments to Enhance Plant Nutrition and Crop Production Sustainability.

The European "Green Deal" policies are shifting toward more sustainable and environmentally conscious agricultural practices, reducing the use of chemical fertilizer and pesticides. This implies exploring alternative strategies. One promising alternative to improve plant nutrition and reinforce plant defenses is the use of beneficial microorganisms in the rhizosphere, such as "Plant-growth-promoting rhizobacteria and fungi". Despite the great abundance of iron (Fe) in the Earth's crust, its poor solubility in calcareous soil makes Fe deficiency a major agricultural issue worldwide. Among plant promoting microorganisms, the yeast Debaryomyces hansenii has been very recently incorporated, for its ability to induce morphological and physiological key responses to Fe deficiency in plants, under hydroponic culture conditions. The present work takes it a step further and explores the potential of D. hansenii to improve plant nutrition and stimulate growth in cucumber plants grown in calcareous soil, where ferric chlorosis is common. Additionally, the study examines D. hansenii's ability to induce systemic resistance (ISR) through a comparative relative expression study by qRT-PCR of ethylene (ET) biosynthesis (ACO1), or ET signaling (EIN2 and EIN3), and salicylic acid (SA) biosynthesis (PAL)-related genes. The results mark a significant milestone since D. hansenii not only enhances nutrient uptake and stimulates plant growth and flower development but could also amplify induced systemic resistance (ISR). Although there is still much work ahead, these findings make D. hansenii a promising candidate to be used for sustainable and environmentally friendly integrated crop management.

Enhancing iron content and growth of cucumber seedlings with MgFe-LDHs under low-temperature stress.

The development of cost-effective and eco-friendly fertilizers is crucial for enhancing iron (Fe) uptake in crops and can help alleviate dietary Fe deficiencies, especially in populations with limited access to meat. This study focused on the application of MgFe-layered double hydroxide nanoparticles (MgFe-LDHs) as a potential solution. We successfully synthesized and characterized MgFe-LDHs and observed that 1-10mg/L MgFe-LDHs improved cucumber seed germination and water uptake. Notably, the application of 10mg/L MgFe-LDHs to roots significantly increased the seedling emergence rate and growth under low-temperature stress. The application of 10mg/L MgFe-LDHs during sowing increased the root length, lateral root number, root fresh weight, aboveground fresh weight, and hypocotyl length under low-temperature stress. A comprehensive analysis integrating plant physiology, nutrition, and transcriptomics suggested that MgFe-LDHs improve cold tolerance by upregulating SA to stimulate CsFAD3 expression, elevating GA3 levels for enhanced nitrogen metabolism and protein synthesis, and reducing levels of ABA and JA to support seedling emergence rate and growth, along with increasing the expression and activity of peroxidase genes. SEM and FTIR further confirmed the adsorption of MgFe-LDHs onto the root hairs in the mature zone of the root apex. Remarkably, MgFe-LDHs application led to a 46% increase (p < 0.05) in the Fe content within cucumber seedlings, a phenomenon not observed with comparable iron salt solutions, suggesting that the nanocrystalline nature of MgFe-LDHs enhances their absorption efficiency in plants. Additionally, MgFe-LDHs significantly increased the nitrogen (N) content of the seedlings by 12% (p < 0.05), promoting nitrogen fixation in the cucumber seedlings. These results pave the way for the development and use of LDH-based Fe fertilizers.

Apo-siderophores promote growth of iron-deficient Arabidopsis plants by mobilizing iron from roots to shoots and reducing oxidative stress in roots

Iron (Fe) is an essential micronutrient for most organisms that is, however, poorly bioavailable in the soil. Acquiring this element is therefore a major issue for both plants and microorganisms. Bacteria acquire Fe by secreting siderophores that chelate the ferric ion with a high affinity and that can contribute to Fe nutrition in plants, under certain conditions including stressful ones. Our previous work has shown that pyoverdine, a siderophore purified from a beneficial Pseudomonas sp., leads to plant growth stimulation when supplied in its Fe-free form (apo-pyoverdine/apopyo) to Arabidopsis thaliana plants grown hydroponically under Fe-deficient conditions. To better understand siderophore-mediated growth promotion, we studied the impact of an apo-siderophore with a different structure from pyoverdine, deferoxamine (DFO), on the same model. Here we show that growth stimulation is linked to the ability of siderophores to chelate Fe, as DFO also promotes growth after 3 to 6 days when provided at 25 µM to 4-week-old A. thaliana plants starved for Fe for 1 to 7 days. The extent to which the siderophore stimulates root and shoot growth depends on the amount of Fe stored in the roots prior to the addition of DFO, and likely involves the remobilization of Fe from the roots to the shoots. The promotion of root growth by DFO does not appear to depend on coumarin production or secretion, but is associated with an increase in the expression of genes of the HOMOLOG OF BEE2 INTERACTING WITH IBH1 (HBI1)-dependent brassinosteroid signaling pathway. DFO stimulates lateral root elongation concomitant with a significant decrease in hydrogen peroxide (H2O2) and oxidized glutathione levels and a decrease in stress-related gene expression in roots. In addition, DFO decreases the expression of the UPBEAT (UPB1) gene involved in H2O2-mediated root growth inhibition, and thus lifts the inhibition of the expression of its target genes, the class III peroxidases that stimulate root growth. Overall, this work indicates that growth promotion by apo-siderophores in an iron-poor environment is likely linked to their ability to induce a stronger response to Fe deficiency while decreasing oxidative stress in roots, thus stimulating Fe remobilization from root Fe pools to shoots and promoting secondary root growth.