Iron Deficiency In Plants Research Articles

UBC18 E2 conjugating enzyme depends on SINAT1 E3 ligase to destabilize the ESCRT component FREE1 in plant iron deficiency responses.

E2 ubiquitin-conjugating enzymes play a crucial role in the ubiquitination process by catalyzing ubiquitin transfer. Although the function of ubiquitin-protein ligases (E3s) in plants response to diverse abiotic stress by targeting specific substrates has been well studied, the involvement of E2s in environmental responses and their downstream targets are not well understood. In this study, we demonstrated that the E2 ubiquitin-conjugating enzyme 18 (UBC18) influences the stability of FREE1 to modulate iron deficiency stress. UBC18 affects the ubiquitination of FREE1 and promotes its degradation, and overexpression of UBC18 decreases plants' sensitivity to iron deficiency by reducing FREE1 level, whereas the ubc18 mutant exhibits sensitivity due to elevated FREE1 accumulation. This study also identified that lysine residues K227, K295, K315, and K540 are required for FREE1 ubiquitination and stability regulation. Mutating these lysine residues in FREE1 resulted in plants' sensitivity to iron starvation. Taken together, our findings shed light on the mechanism of UBC18 in responding to iron deficiency stress by modulating the abundance of FREE1, and further elucidate the role of ubiquitination sites in FREE1 stability regulation and the plant iron deficiency response.

Metabolism of Malus halliana Roots Provides Insights into Iron Deficiency Tolerance Mechanisms.

Iron (Fe) deficiency is one of the most common micronutrient imbalances limiting plant growth globally, especially in arid and saline alkali regions due to the decreased availability of Fe in alkaline soils. Malus halliana grows well in arid regions and is tolerant of Fe deficiency. Here, a physiological and metabolomic approach was used to analyze the short-term molecular response of M. halliana roots to Fe deficiency. On the one hand, physiological data show that the root activity first increased and then decreased with the prolongation of the stress time, but the change trend of root pH was just the opposite. The total Fe content decreased gradually, while the effective Fe decreased at 12 h and increased at 3 d. The activity of iron reductase (FCR) increased with the prolongation of stress. On the other hand, a total of 61, 73, and 45 metabolites were identified by GC-MS in three pairs: R12h (Fe deficiency 12 h) vs. R0h (Fe deficiency 0 h), R3d (Fe deficiency 3 d) vs. R0h, and R3d vs. R12h, respectively. Sucrose, as a source of energy, produces monosaccharides such as glucose by hydrolysis, while glucose accumulates significantly at the first (R12h vs. R0h) and third time points (R3d vs. R0h). Carbohydrates (digalacturonate, L-xylitol, ribitol, D-xylulose, glucose, and glycerol) are degraded into pyruvate through glycolysis and pentose phosphate, which participate in the TCA. Glutathione metabolism and the TCA cycle coordinate with each other, actively respond to Fe deficiency stress, and synthesize secondary metabolites at the same time. This study thoroughly examines the metabolite response to plant iron deficiency, highlighting the crucial roles of sugar metabolism, tricarboxylic acid cycle regulation, and glutathione metabolism in the short-term iron deficiency response of apples. It also lays the groundwork for future research on analyzing iron deficiency tolerance.

Enhancing Agricultural Productivity Through Iron Oxide Nanoparticle Priming: Opportunities, Challenges, and Surface Modification Strategies

The global food crisis is exacerbated by various challenges, including agricultural restrictions and environmental stresses, necessitating innovative approaches to enhance crop development and productivity. One promising technique is seed priming with iron oxide nanoparticles (FeNPs), which has shown significant potential in improving seed germination, crop growth, and stress resistance. This mini-review explores the synthesis, application, and physiological impacts of FeNPs in agriculture, emphasizing their role in addressing iron deficiency in plants and promoting robust plant development under challenging environmental conditions. Despite their benefits, the practical use of FeNPs faces critical challenges, notably nanoparticle agglomeration in biological media, which can diminish their effectiveness and lead to phytotoxicity. This review highlights advanced surface modification strategies, including the use of biocompatible polymers like chitosan and silica encapsulation, to enhance the colloidal stability, reduce agglomeration, and ensure the safe delivery of FeNPs. It discusses the mechanisms by which these modifications improve nanoparticle dispersion and interaction with plant systems, thereby optimizing their agronomic benefits. The review concludes with insights into the future directions of nanoparticle use in seed priming, particularly focusing on the implications of nanoparticle physicochemical properties on their agronomic efficacy and environmental safety.

Design, fabrication and evaluation of a robot for plant nutrient monitoring in greenhouse (case study: Iron nutrient in spinach)

The regulation of nutrients intake in plant life is a critical factor in preserving the quality of crops, enhancing yield rates, and minimizing the fertilizer consumption. Consequently, this research presents the design of an intelligent robot for real-time monitoring of plant nutrients within greenhouse environments. The robot’s ability to detect and address iron deficiency in spinach plants was evaluated. To achieve this, the robot, equipped with a camera, captured visible imaging from surface of spinach plants including both the control group and the group subjected to iron deficiency stress. Statistical analysis of the data was performed at the probability level of 5 %, and genetic algorithm (GA) was utilized to select the most suitable features (G, Area, Energy, Entropy, R and L), from 41 extracted image parameters, including color, morphological, and texture features. An artificial neural network (ANN) was then employed to detect iron deficiency in plants, resulting in an accuracy of 96 %. Subsequently, the Gaussian kernel function of support vector regression (SVR) algorithm was used to predict spinach iron content, yielding the highest determination coefficient (R2 = 0.94) and the lowest values of mean absolute percentage error (MAPE = 5.92), root mean square error (RMSE = 0.43) and standard regression error (SRE = 2.66). The designed robot detected iron-deficient plants with precision, sensitivity, specificity and accuracy of 86 %, 82 %, 84 % and 83 %, respectively. The robot then took the necessary control actions to supply the deficiency of this nutrient by foliar spraying of more than 89 % of the crop area.

Co-planting alters plant iron deficiency in heavy metals contaminated soil amended with sludge

Heavy metals (HMs)-induced iron (Fe) deficiency severely inhibits plant growth and thus hampers phytoremediation and revegetation in HMs-contaminated soil. We conducted a 12-month pot experiment to investigate the effects and mechanisms of co-planting on altering plant HM-induced Fe deficiency. The landscape tree Ilex rotunda was co-planted with Ficus microcarpa and Talipariti tiliaceum in sludge-amended soil. The responses of I. rotunda growth, elements uptake, and rhizosphere microbial community and metabolites were analyzed. The addition of sludge increased cadmium (Cd), zinc (Zn), and nickel (Ni) uptake and induced Fe deficiency-induced chlorosis in I. rotunda. This chlorosis was exacerbated when I. rotunda was co-planted with F. macrocarpa due to the increase in the abundance of sulfate reduction or Fe immobilization-associated bacteria and the relative level of isoprenyl alcohol and atropine in I. rotunda rhizosphere but the decrease in the contents of soil diethylenetriaminepentaacetic acid Fe (DTPA-Fe) (−16.19 %). Co-planting with T. tiliaceum or F. macrocarpa and T. tiliaceum decreased the contents of total or DTPA Zn/Cd/Ni in the soil while increased the contents of soil DTPA-Fe by 13.24 % or 11.34 % and the abundance of microbes which contributed to immobilizing HMs or activating Fe reduction, and then alleviated the chlorosis and the growth inhibition of I. rotunda. These results provide a new perspective on the phytoremediation and revegetation of HMs-contaminated soil.

Cross-Talk between Iron Deficiency Response and Defense Establishment in Plants

Plants are at risk of attack by various pathogenic organisms. During pathogenesis, microorganisms produce molecules with conserved structures that are recognized by plants that then initiate a defense response. Plants also experience iron deficiency. To address problems caused by iron deficiency, plants use two strategies focused on iron absorption from the rhizosphere. Strategy I is based on rhizosphere acidification and iron reduction, whereas Strategy II is based on iron chelation. Pathogenic defense and iron uptake are not isolated phenomena: the antimicrobial phenols are produced by the plant during defense, chelate and solubilize iron; therefore, the production and secretion of these molecules also increase in response to iron deficiency. In contrast, phytohormone jasmonic acid and salicylic acid that induce pathogen-resistant genes also modulate the expression of genes related to iron uptake. Iron deficiency also induces the expression of defense-related genes. Therefore, in the present review, we address the cross-talk that exists between the defense mechanisms of both Systemic Resistance and Systemic Acquired Resistance pathways and the response to iron deficiency in plants, with particular emphasis on the regulation genetic expression.

Using Deep Learning Model to Identify Iron Chlorosis in Plants

Iron deficiency in plants causes iron chlorosis which frequently occurs in soils that are alkaline (pH greater than 7.0) and that contain lime. This deficiency turns affected plant leaves to yellow, or with brown edges in advanced stages. The goal of this research is to use the deep learning model to identify a nutrient deficiency in plant leaves and perform soil analysis to identify the cause of the deficiency. Two pre-trained deep learning models, Single Shot Detector (SSD) MobileNet v2 and EfficientDet D0, are used to complete this task via transfer learning. This research also contrasts the architecture and performance of the models at each stage and freezes the models for future use. Classification accuracy ranged from 93% to 98% for the SSD Mobilenet v2 model. Although this model took less time to process, its accuracy level was lower. While the EfficientDet D0 model required more processing time, it provided very high classification accuracy for the photos, ranging from 87% to 98.4%. These findings lead to the conclusion that both models are useful for real-time classifications, however, the EfficientDet D0 model may perform significantly better.

Iron deficiency in plants: an update on homeostasis and its regulation by nitric oxide and phytohormones

Iron deficiency in plants: an update on homeostasis and its regulation by nitric oxide and phytohormones

Long-distance mobile mRNA CAX3 modulates iron uptake and zinc compartmentalization.

Iron deficiency in plants can lead to excessive absorption of zinc; however, important details of this mechanism have yet to be elucidated. Here, we report that MdCAX3 mRNA is transported from the leaf to the root, and that MdCAX3 is then activated by MdCXIP1. Suppression of MdCAX3 expression leads to an increase in the root apoplastic pH, which is associated with the iron deficiency response. Notably, overexpression of MdCAX3 does not affect the apoplastic pH in a MdCXIP1 loss-of-function Malus baccata (Mb) mutant that has a deletion in the MdCXIP1 promoter. This deletion in Mb weakens MdCXIP1 expression. Co-expression of MdCAX3 and MdCXIP1 in Mb causes a decrease in the root apoplastic pH. Furthermore, suppressing MdCAX3 in Malus significantly reduces zinc vacuole compartmentalization. We also show that MdCAX3 activated by MdCXIP1 is not only involved in iron uptake, but also in regulating zinc detoxification by compartmentalizing zinc in vacuoles to avoid iron starvation-induced zinc toxicity. Thus, mobile MdCAX3 mRNA is involved in the regulation of iron and zinc homeostasis in response to iron starvation.

Cobalt: An Essential Micronutrient for Plant Growth?

Cobalt is a transition metal located in the fourth row of the periodic table and is a neighbor of iron and nickel. It has been considered an essential element for prokaryotes, human beings, and other mammals, but its essentiality for plants remains obscure. In this article, we proposed that cobalt (Co) is a potentially essential micronutrient of plants. Co is essential for the growth of many lower plants, such as marine algal species including diatoms, chrysophytes, and dinoflagellates, as well as for higher plants in the family Fabaceae or Leguminosae. The essentiality to leguminous plants is attributed to its role in nitrogen (N) fixation by symbiotic microbes, primarily rhizobia. Co is an integral component of cobalamin or vitamin B12, which is required by several enzymes involved in N2 fixation. In addition to symbiosis, a group of N2 fixing bacteria known as diazotrophs is able to situate in plant tissue as endophytes or closely associated with roots of plants including economically important crops, such as barley, corn, rice, sugarcane, and wheat. Their action in N2 fixation provides crops with the macronutrient of N. Co is a component of several enzymes and proteins, participating in plant metabolism. Plants may exhibit Co deficiency if there is a severe limitation in Co supply. Conversely, Co is toxic to plants at higher concentrations. High levels of Co result in pale-colored leaves, discolored veins, and the loss of leaves and can also cause iron deficiency in plants. It is anticipated that with the advance of omics, Co as a constitute of enzymes and proteins and its specific role in plant metabolism will be exclusively revealed. The confirmation of Co as an essential micronutrient will enrich our understanding of plant mineral nutrition and improve our practice in crop production.

Autophagy Mediates the Degradation of Plant ESCRT Component FREE1 in Response to Iron Deficiency.

Multivesicular body (MVB)-mediated endosomal sorting and macroautophagy are the main pathways mediating the transport of cellular components to the vacuole and are essential for maintaining cellular homeostasis. The interplay of these two pathways remains poorly understood in plants. In this study, we show that FYVE DOMAIN PROTEIN REQUIRED FOR ENDOSOMAL SORTING 1 (FREE1), which was previously identified as a plant-specific component of the endosomal sorting complex required for transport (ESCRT), essential for MVB biogenesis and plant growth, can be transported to the vacuole for degradation in response to iron deficiency. The vacuolar transport of ubiquitinated FREE1 protein is mediated by the autophagy pathway. As a consequence, the autophagy deficient mutants, atg5-1 and atg7-2, accumulate more endogenous FREE1 protein and display hypersensitivity to iron deficiency. Furthermore, under iron-deficient growth condition autophagy related genes are upregulated to promote the autophagic degradation of FREE1, thereby possibly relieving the repressive effect of FREE1 on iron absorption. Collectively, our findings demonstrate a unique regulatory mode of protein turnover of the ESCRT machinery through the autophagy pathway to respond to iron deficiency in plants.

Evaluation of a Legume-Derived Protein Hydrolysate to Mitigate Iron Deficiency in Plants

Biostimulants play an important role in the development of management practices able to reach adequate productivity to meet the food demand of a growing world population, while following a sustainable agriculture model. This work aims to evaluate the effect of a protein hydrolysate derived from legume seeds by enzymatic hydrolysis on plant growth and also to verify its ability to mitigate Fe deficiency, a widespread problem significantly limiting plant growth and crop productivity. Experiments were performed with tomato (Solanum lycopersicum L.—cv. AKRAI F1) and cucumber (Cucumis sativus L.—cv. EKRON F1). The plants were grown hydroponically under adequate or limited Fe supply. Changes in shoot and root fresh weight, leaf relative chlorophyll content and the accumulation of macro- and microelements in shoots and roots were measured. Plant ability to cope with Fe deficiency was measured by evaluating the activity of root Fe3+-chelate reductase. Our results indicate that the foliar treatments with the protein hydrolysate did not significantly affect growth parameters when plants were grown in full nutrient solution. However, the biostimulant was able to improve the growth performance of Fe-deficient plants. Therefore, the protein hydrolysate can be a powerful tool to stimulate crop growth under Fe-deficient environments, leading to reduced fertilizer inputs with related environmental and economic benefits.

SINAT E3 ligases regulate the stability of the ESCRT component FREE1 in response to iron deficiency in plants.

The endosomal sorting complex required for transport (ESCRT) machinery is an ancient, evolutionarily conserved membrane remodeling complex that is essential for multivesicular body (MVB) biogenesis in eukaryotes. FYVE DOMAIN PROTEIN REQUIRED FOR ENDOSOMAL SORTING 1 (FREE1), which was previously identified as a plant-specific ESCRT component, modulates MVB-mediated endosomal sorting and autophagic degradation. Although the basic cellular functions of FREE1 as an ESCRT component have been described, the regulators that control FREE1 turnover remain unknown. Here, we analyzed how FREE1 homeostasis is mediated by the RING-finger E3 ubiquitin ligases, SINA of Arabidopsis thaliana (SINATs), in response to iron deficiency. Under iron-deficient growth conditions, SINAT1-4 were induced and ubiquitinated FREE1, thereby promoting its degradation and relieving the repressive effect of FREE1 on iron absorption. By contrast, SINAT5, another SINAT member that lacks ubiquitin ligase activity due to the absence of the RING domain, functions as a protector protein which stabilizes FREE1. Collectively, our findings uncover a hitherto unknown mechanism of homeostatic regulation of FREE1, and demonstrate a unique regulatory SINAT-FREE1 module that subtly regulates plant response to iron deficiency stress.

Fulvic acid increases iron bioavailability in aquaponic systems: Theoretical designs and practical considerations to prevent iron deficiency in plants

Plants grown in aquaponics frequently develop iron deficiency, which is generally corrected via supplementation with iron chelates. However, the solid waste excreted by fish contains considerable amounts iron, which are lost in the system by precipitation of insoluble iron oxides. Thus, the present study proposed the use of fulvic acid (FA), a humic substance with metal complexing capacity, to prevent iron precipitation and enhance its bioavailability in the aquaculture wastewater. An aquaponic solution was added with levels of fulvic acid (0, 69, 138, 345, and 690 mg L−1), and analyzed for dissolved iron after incubation and centrifugation. Visual MINTEQ was used to characterize and quantify the effect of fulvic acid levels on iron precipitation, species of possible solid forms, and concentration of dissolved bioavailable iron forms. Dissolved iron concentration increased with the inclusion of fulvic acid in the nutrient solution, and the highest iron concentration (22.4 μM) was obtained by treating the solution with 690 mg L−1 of fulvic acid. Visual MINTEQ simulations demonstrated that, in the absence of fulvic acid, iron precipitated in the form of αFe2O3, and the concentration of available iron increased with the inclusion of FA due to its complexing properties. Solution pH had no effect on iron availability with the absence of fulvic acid; in its presence, the effect of pH was only significant at values below 4.5. This study shows that fulvic acid seems to play an important role in transporting low-soluble iron from fish tanks to plant roots in aquaponic systems.

Putative cis-Regulatory Elements Predict Iron Deficiency Responses in Arabidopsis Roots.

Plant iron deficiency (-Fe) activates a complex regulatory network that coordinates root Fe uptake and distribution to sink tissues. In Arabidopsis (Arabidopsis thaliana), FER-LIKE FE DEFICIENCY-INDUCED TRANSCRIPTION FACTOR (FIT), a basic helix-loop-helix (bHLH) transcription factor (TF), regulates root Fe acquisition genes. Many other -Fe-induced genes are FIT independent, and instead regulated by other bHLH TFs and by yet unknown TFs. The cis-regulatory code, that is, the cis-regulatory elements (CREs) and their combinations that regulate plant -Fe-responses, remains largely elusive. Using Arabidopsis root transcriptome data and coexpression clustering, we identified over 100 putative CREs (pCREs) that predicted -Fe-induced gene expression in computational models. To assess pCRE properties and possible functions, we used large-scale in vitro TF binding data, positional bias, and evolutionary conservation. As one example, our approach uncovered pCREs resembling IDE1 (iron deficiency-responsive element 1), a known grass -Fe response CRE. Arabidopsis IDE1-likes were associated with FIT-dependent gene expression, more specifically with biosynthesis of Fe-chelating compounds. Thus, IDE1 seems to be conserved in grass and nongrass species. Our pCREs matched among others in vitro binding sites of B3, NAC, bZIP, and TCP TFs, which might be regulators of -Fe responses. Altogether, our findings provide a comprehensive source of cis-regulatory information for -Fe-responsive genes that advance our mechanistic understanding and inform future efforts in engineering plants with more efficient Fe uptake or transport systems.

Effects of Rahnella aquatilis JZ-GX1 on Treat Chlorosis Induced by Iron Deficiency in Cinnamomum camphora

With the increasing popularity of urban landscaping, there is a greater need to address iron deficiency and chlorosis in Cinnamomum camphora. Beneficial microorganisms can play an important role in improving plant iron nutrition. In this study, we evaluated the greening effect that results from inoculating C. camphora with Rahnella aquatilis JZ-GX1. We conducted in vitro experiments to determine the effectiveness of JZ-GX1 in reducing extracellular iron(III) ions in siderophores and producing organic acids under low-iron conditions. Potted, chlorotic C. camphora seedlings were inoculated, and parameters related to growth and iron nutritional status were measured. Inoculation by JZ-GX1 had a more pronounced greening effect on C. camphora than the traditional iron sulfate treatment for plant iron deficiency. Inoculated plants exhibited higher levels of active iron in the leaves, enhanced rhizosphere acidification capacity and ferric chelate reductase activity. Furthermore, the complete root system and chloroplast developmental structures were observed. Our results demonstrate the potential roles of R. aquatilis JZ-GX1 in promoting iron absorption in C. camphora.

Progress in bHLH transcription factors regulating the response to iron deficiency in plants

Iron is one of the essential mineral micronutrients for plants. Low concentrations of effective iron in soil can easily increase risk of plant iron deficiency. Several members of bHLH transcription factors family participate in the response to iron deficiency and play an important role in iron regulation of plants. In order to better understand the mechanism of iron deficiency response, an overview of the structure, classification, function and regulatory mechanism of bHLH transcription factors was given in this review as well as signaling pathway triggered by iron deficiency. It will provide theoretical basis and design strategies for cultivating iron deficiency tolerant or iron-rich crops using bHLH transcription factors.

Biosynthesis of redox-active metabolites in response to iron deficiency in plants.

Iron is an essential but poorly bioavailable nutrient due to its low solubility, especially in alkaline soils. Here, we describe the discovery of a novel redox-active catecholic metabolite, termed sideretin, which derives from the coumarin fraxetin, and is the primary molecule exuded by Arabidopsis thaliana roots in response to iron deficiency. We have identified two enzymes that complete the biosynthetic pathway of fraxetin and sideretin. Chemical characterization of fraxetin and sideretin, and biological assays with pathway mutants, suggest that these coumarins are critical for iron nutrition in A. thaliana. Further, we show that sideretin production occurs in eudicot species only distantly related to A. thaliana. Untargeted metabolomics of the root exudates of various eudicots revealed production of structurally diverse redox-active molecules in response to iron deficiency. Our results indicate that secretion of small-molecule reductants by roots may be a widespread and previously underappreciated component of reduction-based iron uptake.

Complementary Evaluation of Iron Deficiency Root Responses to Assess the Effectiveness of Different Iron Foliar Applications for Chlorosis Remediation.

Iron deficiency in plants is caused by a low availability of iron in the soil, and its main visual symptom is leaf yellowing due to a decrease in chlorophyll content, along with a reduction in plant growth and fruit quality. Foliar sprays with Fe compounds are an economic alternative to the treatment with expensive synthetic Fe-chelates applied to the soil, although the efficacy of foliar treatments is rather limited. Generally, plant response to Fe-foliar treatments is monitored by measuring chlorophyll content (or related parameters as SPAD index). However, different studies have shown that foliar Fe sprays cause a local regreening and that translocation of the applied Fe within the plant is quite low. In this context, the aim of this study was to assess the effects of foliar applications of different Fe compounds [FeSO4, Fe(III)-EDTA, and Fe(III)-heptagluconate] on Fe-deficient cucumber plants, by studying the main physiological plant root responses to Fe deficiency [root Fe(III) chelate reductase (FCR) activity; acidification of the nutrient solution; and expression of the Fe deficiency responsive genes encoding FCR, CsFRO1, Fe(II) root transporter CsIRT1, and two plasma membrane H+-ATPases, CsHA1 and CsHA2], along with SPAD index, plant growth and Fe content. The results showed that the overall assessment of Fe-deficiency root responses improved the evaluation of the efficacy of the Fe-foliar treatments compared to just monitoring SPAD indexes. Thus, FCR activity and expression of Fe-deficiency response genes, especially CsFRO1 and CsHA1, preceded the trend of SPAD index and acted as indicators of whether the plant was sensing or not metabolically active Fe due to the treatments. Principal component analysis of the data also provided a graphical tool to evaluate the evolution of plant responses to foliar Fe treatments with time.

The Understanding of the Plant Iron Deficiency Responses in Strategy I Plants and the Role of Ethylene in This Process by Omic Approaches.

Iron (Fe) is an essential plant micronutrient but is toxic in excess. Fe deficiency chlorosis is a major constraint for plant growth and causes severe losses of crop yields and quality. Under Fe deficiency conditions, plants have developed sophisticated mechanisms to keep cellular Fe homeostasis via various physiological, morphological, metabolic, and gene expression changes to facilitate the availability of Fe. Ethylene has been found to be involved in the Fe deficiency responses of plants through pharmacological studies or by the use of ethylene mutants. However, how ethylene is involved in the regulations of Fe starvation responses remains not fully understood. Over the past decade, omics approaches, mainly focusing on the RNA and protein levels, have been used extensively to investigate global gene expression changes under Fe-limiting conditions, and thousands of genes have been found to be regulated by Fe status. Similarly, proteome profiles have uncovered several hallmark processes that help plants adapt to Fe shortage. To find out how ethylene participates in the Fe deficiency response and explore putatively novel regulators for further investigation, this review emphasizes the integration of those genes and proteins, derived from omics approaches, regulated both by Fe deficiency, and ethylene into a systemic network by gene co-expression analysis.