Fe Deficiency Research Articles

Silencing of FRO1 gene affects iron homeostasis and nutrient balance in tomato plants

AbstractBackgroundIron chlorosis is an abiotic stress of worldwide importance affecting several agronomic crops. It is important to understand how plants maintain nutrient homeostasis under Fe deficiency and recovery.AimsWe used the virus‐induced gene silencing (VIGS) method to elucidate the role of the FRO1 gene in tomato plants and identify the impact on regulation of the root ferric‐chelate reductase (FCR) activity and nutritional homeostasis.MethodsTomato plantlets cv. “Cherry” were transferred into half‐strength Hoagland's nutrient solution containing 0.5 µM of Fe (Fe0.5). In phase I, two treatments were established: control (Fe0.5) plants and VIGS‐0.5 plants corresponding to plants with the FRO1 gene silenced. In phase II, plants from Fe0.5 and VIGS‐0.5 were transferred to new nutrient solution and then grown for a further 14 days under 0 and 10 µM of Fe (as 0.5 µM would not be enough for the larger plants during phase II). Therefore, four treatments were imposed: Fe0, Fe10, VIGS‐0, and VIGS‐10.ResultsVIGS‐0.5 plants had significantly lower chlorophyll (Chl) and root FCR activity compared to the respective non‐silenced plants and retained more Cu and Zn in the roots at the expense of stems (Cu) or young leaves (Zn). Iron concentration in roots and stems decreased in FRO1 gene‐silenced plants, compared to control plants, but the allocation to different organs was similar in both treatments.ConclusionsThere was a partial recovery of leaf Chl in the VIGS‐10 plants and a higher concentration of Fe in all organs. In contrast, the allocation of Cu to roots decreased in the VIGS‐10 plants.

Entomopathogenic Fungus-Related Priming Defense Mechanisms in Cucurbits Impact Spodoptera littoralis (Boisduval) Fitness.

Entomopathogenic fungi (EPF) exhibit direct and indirect mechanisms to increase plant resistance against biotic and abiotic stresses. Plant responses to these stresses are interconnected by common regulators such as ethylene (ET), which is involved in both iron (Fe) deficiency and induced systemic resistance responses. In this work, the roots of cucurbit seedlings were primed with Metarhizium brunneum (EAMa 01/58-Su strain), and relative expression levels of 18 genes related to ethylene (ET), jasmonic acid (JA), and salicylic acid (SA) synthesis, as well as pathogen-related (PR) protein genes, were studied by reverse transcription-quantitative PCR (qRT-PCR). Effects of priming on Spodoptera littoralis were studied by feeding larvae for 15 days with primed and control plants. Genes showed upregulation in studied species; however, the highest relative expression was observed in roots and shoots of plants with Fe deficiency, demonstrating the complexity and the overlapping degree of the regulatory network. EIN2 and EIN3 should be highlighted; both are key genes of the ET transduction pathway that enhanced their expression levels up to eight and four times, respectively, in shoots of primed cucumber. Also, JA and SA synthesis and PR genes showed significant upregulation during the observation period (e.g., the JA gene LOX1 increased 506 times). Survival and fitness of S. littoralis were affected with significant effects on mortality of larvae fed on primed plants versus controls, length of the larval stage, pupal weight, and the percentage of abnormal pupae. These results highlight the role of the EAMa 01/58-Su strain in the induction of resistance, which could be translated into direct benefits for plant development. IMPORTANCE Entomopathogenic fungi are multipurpose microorganisms with direct and indirect effects on insect pests. Also, EPF provide multiple benefits to plants by solubilizing minerals and facilitating nutrient acquisition. A very interesting and novel effect of these fungi is the enhancement of plant defense systems by inducing systematic and acquired resistance. However, little is known about this function. This study sheds light on the molecular mechanisms involved in cucurbits plants' defense activation after being primed by the EPF M. brunneum. Furthermore, the subsequent effects on the fitness of the lepidopteran pest S. littoralis are shown. In this regard, a significant upregulation was recorded for the genes that regulate JA, SA, and ET pathways. This increased expression of defense genes caused lethal and sublethal effects on S. littoralis. This could be considered an added value for the implementation of EPF in integrated pest management programs.

Predicting iron deficiency and oxidative stress in Glycine max through Fourier transform infrared spectroscopy in a time-course experiment

AimsThe excessive use of fertilizers is a problem in current agricultural systems, and sustainable farming practices, including precision agriculture, demand the use of new technologies to manage plant stress at an early stage. To sustainably manage iron (Fe) fertilization in agricultural fields, it is urgent to develop early detection methods for Fe deficiency, and linked oxidative stress, in plant leaves. Herein, the potential of using Fourier Transform Infrared (FTIR) spectroscopy for Fe deficiency and oxidative stress detection in soybean plants was evaluated.MethodsAfter a period of two weeks of hydroponic growth under optimum conditions, soybean plants were grown under Fe-sufficient (Fe+) and Fe-deficient (Fe–) hydroponic conditions for four weeks. Sampling occurred every week, infrared (IR) spectra were acquired and biological parameters (total chlorophyll, anthocyanins and carotenoids concentration, and ABTS and DPPH free radical scavenging ability), mineral concentrations, and the Fe-related genes’ expression - FRO2- and IRT1-like - were evaluated.ResultsTwo weeks after imposing Fe deficiency, plants displayed decreased antioxidant activity, and increased expression levels of FRO2- and IRT1-like genes. Regarding the PLS models developed to estimate the biological parameters and mineral concentrations, satisfactory calibration models were globally obtained with R2C from 0.93 to 0.99. FTIR spectroscopy was also able to discriminate between Fe + and Fe– plants from an early stage of stress induction with 96.3% of correct assignments.ConclusionHigh reproducibility was observed among the different spectra of each sample and FTIR spectroscopy may be an early, non-invasive, cheap, and environmentally friendly technique for IDC management.

BRUTUS-LIKE (BTSL) E3 ligase-mediated fine-tuning of Fe regulation negatively affects Zn tolerance of Arabidopsis.

The mineral micronutrients zinc (Zn) and iron (Fe) are essential for plant growth and human nutrition, but interactions between the homeostatic networks of these two elements are not fully understood. Here we show that loss of function of BTSL1 and BTSL2, which encode partially redundant E3 ubiquitin ligases that negatively regulate Fe uptake, confers tolerance to Zn excess in Arabidopsis thaliana. Double btsl1 btsl2 mutant seedlings grown on high Zn medium accumulated similar amounts of Zn in roots and shoots to the wild type, but suppressed the accumulation of excess Fe in roots. RNA-sequencing analysis showed that roots of mutant seedlings had relatively higher expression of genes involved in Fe uptake (IRT1, FRO2, and NAS) and in Zn storage (MTP3 and ZIF1). Surprisingly, mutant shoots did not show the transcriptional Fe deficiency response which is normally induced by Zn excess. Split-root experiments suggested that within roots the BTSL proteins act locally and downstream of systemic Fe deficiency signals. Together, our data show that constitutive low-level induction of the Fe deficiency response protects btsl1 btsl2 mutants from Zn toxicity. We propose that BTSL protein function is disadvantageous in situations of external Zn and Fe imbalances, and formulate a general model for Zn-Fe interactions in plants.

MxMPK6-2-mediated phosphorylation enhances the responseof apple rootstocks to Fe deficiency by activating PM H+ -ATPase MxHA2.

Iron (Fe) deficiency significantly affects the growth and development, fruit yield and quality of apples. Apple roots respond to Fe deficiency stress by promoting H+ secretion, which acidifies the soil. In this study, the plasma membrane (PM) H+ -ATPase MxHA2 promoted H+ secretion and root acidification of apple rootstocks under Fe deficiency stress. H+ -ATPase MxHA2 is upregulated in Fe-efficient apple rootstock of Malus xiaojinensis at the transcription level. Fe deficiency also induced kinase MxMPK6-2, a positive regulator in Fe absorption that can interact with MxHA2. However, the mechanism involving these two factors under Fe deficiency stress is unclear. MxMPK6-2 overexpression in apple roots positively regulated PM H+ -ATPase activity, thus enhancing root acidification under Fe deficiency stress. Moreover, co-expression of MxMPK6-2 and MxHA2 in apple rootstocks further enhanced PM H+ -ATPase activity under Fe deficiency. MxMPK6-2 phosphorylated MxHA2 at the Ser909 site of C terminus, Thr320 and Thr412 sites of the Central loop region. Phosphorylation at the Ser909 and Thr320 promoted PM H+ -ATPase activity, while phosphorylation at Thr412 inhibited PM H+ -ATPase activity. MxMPK6-2 also phosphorylated the Fe deficiency-induced transcription factor MxbHLH104 at the Ser169 site, which then could bind to the promoter of MxHA2, thus enhancing MxHA2 upregulation. In conclusion, the MAP kinase MxMPK6-2-mediated phosphorylation directly and indirectly regulates PM H+ -ATPase MxHA2 activity at the protein post-translation and transcription levels, thus synergistically enhancing root acidification under Fe deficiency stress.

Production of iron-peptide complexes from spent yeast for nutraceutical industry

Iron (Fe) deficiencies are a major health condition concern and over the years many solutions in the form of Fe supplementation have been investigated. Organic Fe-complexes are the most promising for Fe deficiencies remediation. The aim of present study was to value peptide rich waste streams from β-glucan and mannan production from spent yeast (Gpep and Mpep, respectively) as Fe-peptide complexes for Fe supplementation. These waste streams were first subjected to ultrafiltration treatment before assessing the capacity of these fractions to complex Fe was evaluated, without, and with nitrogen. Results have shown that Gpep> 1 kDa was the best fraction with a optimal pH of 6.0 and a time of 30 min. The resulting Fe-peptide complex was characterized using powder XDR, fluorescence, FTIR, SEM and Mastersizer Laser Diffraction. Results have shown that Gpep and Mpep waste streams have potential application as Fe supplementation in the form of Fe peptide complexes.

Effect of Phosphorus, Iron, Zinc, and Their Combined Deficiencies on Photosynthetic Characteristics of Rice (Oryza sativa L.) Seedlings

Combined elemental deficiencies are more complex and insidious physiological metabolic responses than single elemental stresses. To determine the effects of phosphorus (P), iron (Fe), zinc (Zn), and their deficient combinations on photosynthetic characteristics of rice seedlings, we investigated their effects on dry weight, chlorophyll (Chl) content, rapid photosynthetic carbon assimilation CO2 responses, and Chl fluorescence in four-week-old rice (CB9 and BJ1 cultivars) seedlings. The results showed that the dry matter, maximum carboxylation efficiency (Vc,max), and maximum electron transfer efficiency (Jmax) of seedlings were all reduced to different degrees under the element deficiency treatments. JIP-test analysis showed that the decrease in the concentration of active PSII reaction centers (RC/ABS) under -Zn treatment was the main reason for the inhibition of performance index PIABS. The -P treatment reduced RC/ABS and inhibited electron transfer (ψEo). Primary photochemical reactions (φPo) of -P-Zn treated seedlings were also inhibited compared to the -P treatment. The -Fe and -Fe-Zn treatments inhibited photosynthesis most severely, which not only reduced RC/ABS but also severely inhibited φPo and ψEo. Notably, the -P-Fe and -P-Fe-Zn treatments of the CB9 improved the RC/ABS, alleviating the limitation of Fe deficiency. These results help enhance the understanding of the complex relationship between nutrient balance and photosynthesis, especially for P, Fe, Zn, and their combined deficiency.

#5517 IN CHRONIC KIDNEY DISEASE, IRON DEFICIENCY-INDUCED ANEMIA IS ASSOCIATED WITH HIGHER LEVELS OF FGF23 THAT ARE NOT REDUCED BY IRON ADMINISTRATION

Abstract Background and Aims Iron (Fe) deficiency significantly contributes to anemia in chronic kidney disease (CKD). High FGF23 levels, commonly found in CKD, are related to adverse outcomes in patients. In the normal setting, an association between Fe deficiency and FGF23 has been observed. However, it is unknown whether Fe deficiency-induced anemia might contribute to the excessive FGF23 levels in CKD. Thus, this study was intended to evaluate the interplay between Fe deficiency, CKD, and FGF23. Method Male Wistar rats with normal renal function received either standard (40 ppm Fe) or Fe-deficient (4 ppm Fe) diets for 6 weeks to induce anemia. Then, several normal and all the anemic rats were switched to an adenine-enriched (0.6%) diet to induce renal damage. Groups of anemic-uremic animals were treated with oral (ferric citrate, FC and ferrous sulfate, FS) or intravenous (ferric carboxymaltose, FCx) Fe at a dose of 9 mg/kg for 5 weeks. Hematological and mineral metabolism parameters were determined at sacrifice. All experimental protocols were approved by the Ethics Committee for Animal Research of the University of Córdoba. Results Plasma and serum biochemistries are shown in Table 1. CKD per se was associated with derangements in hematological parameters. The presence of Fe deficiency-induced anemia further decreased these parameters, being statistically significant in the case of serum Fe (P = 0.003). Iron therapy improved hematocrit, hemoglobin, and Fe levels, although statistical significance for all of them was only reached when FC was administered (P = 0.012, P = 0.038, and P = 0.002, respectively). As expected, CKD rats exhibited disturbances in mineral metabolism. Interestingly, uremic and anemic rats showed higher intact (P = 0.039) and c-terminal (P = 0.048) FGF23 levels when compared with CKD group. Despite normalization of serum Fe, intact FGF23 further increased following administration of FS (P = 0.022), and same trend was observed with all the compounds. However, cFGF23 levels remained unchanged in all the Fe-treated groups. Conclusion The presence of Fe-induced anemia in an experimental model of CKD is associated with further increases in the levels of both intact and c-terminal FGF23. Thus, other factors distinct than serum Fe might influence FGF23 levels. Our results support the need for investigating the precise mechanisms underlying the relationship between Fe and FGF23 to optimize the clinical management of anemia, particularly in the context of renal dysfunction.

Calcium-dependent protein kinases CPK21 and CPK23 phosphorylate and activate the iron-regulated transporter IRT1 to regulate iron deficiency in Arabidopsis.

Iron (Fe) is an essential micronutrient for all organisms. Fe availability in the soil is usually much lower than that required for plant growth, and Fe deficiencies seriously restrict crop growth and yield. Calcium (Ca2+) is a second messenger in all eukaryotes; however, it remains largely unknown how Ca2+ regulates Fe deficiency. In this study, mutations in CPK21 and CPK23, which are two highly homologous calcium-dependent protein kinases, conferredimpaired growth and rootdevelopment under Fe-deficient conditions, whereas constitutively active CPK21 and CPK23 enhanced plant tolerance to Fe-deficient conditions. Furthermore, we found that CPK21 and CPK23 interacted with and phosphorylated the Fe transporter IRON-REGULATED TRANSPORTER1 (IRT1) at the Ser149 residue. Biochemical analyses and complementation of Fe transport in yeast and plants indicated that IRT1 Ser149 is critical for IRT1 transport activity. Taken together, these findings suggest that the CPK21/23-IRT1 signaling pathway is critical for Fe homeostasis in plants and provides targets for improving Fe-deficient environments and breeding crops resistant to Fe-deficient conditions.

Rho of plant GTPase MxROP1 regulates the responses to Fe deficiency by targeting Zinc Ribbon 3 in apple rootstocks

The Rho-related GTPase of plants (ROPs) is a multifunctional molecular switch that can regulate plant growth, development, and responses to the environment. However, how the ROPs regulate the response to Fe deficiency has not been thoroughly clarified. In this study, we found that Fe deficiency induced MxROP1 in apple (Malus xiaojinensis) at both the transcriptional and translational levels. The overexpression of MxROP1, MxROP1DN (inactive form), and MxROP1CA (active form) in apple roots increased the activity of ferric chelate reductase and the ability to acidify the rhizosphere, and the lines that overexpressed MxROP1DN exhibited the strongest reaction to enhanced Fe uptake. Yeast two-hybrid library screening indicated that MxROP1 interacted with MxZR3.1, a DNL zinc finger protein that negatively regulates the responses to Fe deficiency. We identified their interaction in vitro and in vivo in more detail using pull-down and bimolecular fluorescence complementation assays, respectively, and MxROP1DN-MxZR3.1 interacted the most strongly. Furthermore, MxROP1 negatively affected the stability of MxZR3.1 protein in vitro as shown by a cell semi-degradation assay, and the application of MG132 inhibited the degradation of MxZR3.1-HIS proteins. This indicated that MxROP1 caused the degradation of MxZR3.1 protein through the 26 S proteasome pathway. Similar results were found in OE-MxROP1+OE-MxZR3.1 transgenic apple calli compared with those in the OE-MxZR3.1 calli. We also demonstrated that MxZR3.1 interacted with MxbHLH39, a known positive transcription factor and core component of Fe deficiency, and MxROP1 affected the interaction of MxZR3.1-MxbHLH39 as shown in a competitive binding assay. Τhis clarified one MxROP1-MxZR3.1-MxbHLH39 pathway that maintains Fe homeostasis in M. xiaojinensis.

Influence of iron seed priming on seed germination, growth and iron content in rice seedlings

The area under direct-seeded aerobic rice (DSR) is increasing in Indo-gangetic plains due to labor and water scarcity. However, iron (Fe) deficiency is a severe problem in DSR under coarse-textured soils, resulting in poor germination, interveinal chlorosis, and poor seedling establishment. Fe seed priming is a better option to ensure higher seed germination and optimum supply of Fe at initial growth stages. Hence, the experiment was conducted with seven seed priming treatments i.e. Control (hydropriming), 0.5% Fe through ferrous sulfate (FeSO4 7H2O), 1.0% Fe through FeSO4 7H2O, 0.25% Fe through ethylene diamine tetra acetic acid chelated iron (Fe-EDTA), 0.5% Fe through Fe-EDTA, 0.025% Fe through iron oxide nanoparticle (FeO NPs) and 0.05% Fe through FeO NPs. The Fe seed priming showed a significant increase in Fe content of paddy seeds over the hydropriming treatment. Among different treatments, FeSO4.7H2O (1.0% Fe) showed highest germination percentage (91.3%), root length (8.4%) and shoot length (9.4%) followed by FeSO4.7H2O (0.5% Fe) which was significantly higher over the control. But, the treatment involving Fe-EDTA (0.5% Fe) showed adverse effects on germination and seedling growth. Ferrous (Fe2+) iron and total Fe content in rice seedlings showed similar trends to total Fe content in primed seeds treated with different Fe sources. Thus, Fe seed priming of rice with FeSO4.7H2O (1.0%Fe) for 12 h was effective for higher germination percentage, greater iron content at initial growth stages and ameliorated the Fe deficiency in direct seeded aerobic rice.

Iron toxicity downregulates root-proton efflux and decreases zinc accumulation in cassava

Iron (Fe) plays a pivotal role in biogeochemical cycling in the soil-plant-human continuum; however, much research has focused on Fe deficiency with limited knowledge about Fe toxicity impacts on micronutrient (e.g., zinc: Zn) accumulation in cassava, an important staple tuber food in the Tropics. A sand-hydroponic-hybrid technique was undertaken for 60 days to investigate the effects of variable Fe concentrations (0.1–500 μmol Fe L−1) on the root-proton and root-organic acid release, rhizosphere Fe solubility, and levels of cassava nutrient accumulation. The results showed that high Fe concentrations (50–500 μmol Fe L−1) significantly decreased the root (0.34–0.51 g dry weight) biomass compared to the control (0.82–0.83 g dry weight). The Fe concentrations significantly regulated the net proton release from the roots by upregulating (25–45 μmol L−1 h−1 g−1 fresh weight root) and downregulating (1.8–7.1 μmol L−1 h−1 g−1 fresh weight root) the net proton efflux at low (1.0 μmol Fe L−1) and high Fe concentrations (500 μmol Fe L−1), respectively. Succinic acid was the sole organic acid observed and only in the Fe-sensitive cultivar. The water-extractable Fe in the rhizosphere sand (average 3.37 mg kg−1) was lower than in the bulk sand (average 5.31 mg kg−1), indicating that net proton efflux controlled rhizosphere Fe solubility. The high Fe concentrations significantly decreased Zn accumulation (20–29 mg Zn kg−1) but increased phosphorus (P) accumulation (2.7–3.4 g P kg−1) in the roots compared to the control (48–59 mg Zn kg−1 and 2.0–2.3 g P kg−1, respectively), implying that Fe toxicity could be responsible for the undernourished Zn content in the tuber. This study suggested the importance of alleviating Fe toxicity in soil-plant systems to mitigate cassava root Zn deficiency, which is relevant to human Zn malnutrition in countries consuming cassava as the main staple diet.

Silicon mitigates iron deficiency in two energy cane cultivars by modulating physiological and nutritional mechanisms.

Alkaline soils with iron (Fe) deficiency are found in many regions of the world, and the use of silicon (Si) can mitigate the damages caused by such deficiency. The aim of this study was to evaluate the effect of Si in mitigating a moderate deficiency of Fe in two energy cane cultivars. Two experiments were performed, one with the VX2 cultivar and the other with the VX3 cultivar of energy cane, which were cultivated in pots with sand and a nutrient solution. In both experiments, treatments followed a factorial scheme 2x2, designed based on the sufficiency and deficiency of Fe, being combined with the absence or presence of Si (2.5 mmol L-1), disposed in a randomized blocks design with six replicates. In the condition of Fe sufficiency, plants were cultivated in a solution containing 368 µmol L-1 of Fe, while plants cultivated under deficiency were initially submitted to cultivation with a 54 µmol L-1 concentration of Fe for 30 days, and later, with Fe complete omission for 60 days. The supply of Si was carried out by applying 15 fertirrigations with Si (via root and leaf) during the initial stage of seedling development, and after transplanting, the nutrient solution was added daily (via root). Both cultivars of energy cane were sensitive to Fe deficiency in the absence of Si, impairing its growth by causing stress and pigment degradation, thus reducing the photosynthesis efficiency. The supply of Si mitigated the damages caused by Fe deficiency in both cultivars, by increasing Fe accumulation in new and intermediate leaves, stem, and roots in the VX2 cultivar, and in new, intermediate, and old leaves and stem in the VX3 cultivar, which in turn reduced stress and favored both the nutritional and photosynthesis efficiency, while increasing the dry matter production. Si by modulating physiological and nutritional mechanisms, mitigates Fe deficiency in two energy cane cultivars. It was concluded that Si can be used as a strategy to improve growth and nutrition of energy cane in environments that are susceptible to Fe deficiency.

Evidence That PbrSAUR72 Contributes to Iron Deficiency Tolerance in Pears by Facilitating Iron Absorption.

Iron is an essential trace element for plants; however, low bioactive Fe in soil continuously places plants in an Fe-deficient environment, triggering oxidative damage. To cope with this, plants make a series of alterations to increase Fe acquisition; however, this regulatory network needs further investigation. In this study, we found notably decreased indoleacetic acid (IAA) content in chlorotic pear (Pyrus bretschneideri Rehd.) leaves caused by Fe deficiency. Furthermore, IAA treatment slightly induced regreening by increasing chlorophyll synthesis and Fe2+ accumulation. At that point, we identified PbrSAUR72 as a key negative effector output of auxin signaling and established its close relationship to Fe deficiency. Furthermore, the transient PbrSAUR72 overexpression could form regreening spots with increased IAA and Fe2+ content in chlorotic pear leaves, whereas its transient silencing does the opposite in normal pear leaves. In addition, cytoplasm-localized PbrSAUR72 exhibits root expression preferences and displays high homology to AtSAUR40/72. This promotes salt tolerance in plants, indicating a putative role for PbrSAUR72 in abiotic stress responses. Indeed, transgenic plants of Solanum lycopersicum and Arabidopsis thaliana overexpressing PbrSAUR72 displayed less sensitivity to Fe deficiency, accompanied by substantially elevated expression of Fe-induced genes, such as FER/FIT, HA, and bHLH39/100. These result in higher ferric chelate reductase and root pH acidification activities, thereby hastening Fe absorption in transgenic plants under an Fe-deficient condition. Moreover, the ectopic overexpression of PbrSAUR72 inhibited reactive oxygen species production in response to Fe deficiency. These findings contribute to a new understanding of PbrSAURs and its involvement in Fe deficiency, providing new insights for the further study of the regulatory mechanisms underlying the Fe deficiency response.

Cadmium, arsenic, and mineral nutrients in rice and potential risks for human health in South China.

Rice (Oryza sativa L.) is one of the most important staple food crops worldwide. For people fed on rice, toxic elements cadmium (Cd) and arsenic (As) and mineral nutrients in rice are pivotal to evaluate potential risks of harmful element intake and malnutrition. We collected rice samples of 208 cultivars (83 inbred and 125 hybrid) from fields in South China and determined Cd, As, As species, and mineral elements in brown rice. Chemical analysis shows that the average content of Cd and As in brown rice were 0.26 ± 0.32 and 0.21 ± 0.08mg·kg-1, respectively. Inorganic As (iAs) was the dominative As species in rice. Rice Cd and iAs in 35.1% and 52.4% of the 208 cultivars exceeded rice Cd and iAs limits, respectively. Significant variations of rice subspecies and regions were found for Cd, As, and mineral nutrients in rice (P < 0.05). Inbred rice had lower As uptake and more balanced mineral nutrition than hybrid species. Significant correlation was observed between Cd, As versus mineral elements like Ca, Zn, B, and Mo (P < 0.05). Health risk assessment indicates that high risks of non-carcinogenic and carcinogenic of Cd and iAs, and malnutrition, in particular Ca, protein and Fe deficiencies, might be caused by rice consumption in South China.

Effects of Citric Acid and Humic-like Substances on Yield, Enzyme Activities, and Expression of Genes Involved in Iron Uptake in Tomato Plants

Iron (Fe) deficiency is a common abiotic stress on plants growing in calcareous soils where low organic matter content, high carbonate–bicarbonate concentration, and high pH precipitate Fe in unavailable forms. Enzymatic activity is a mechanism for plants to access soil nutrients; enzymes such as H+-ATPase, phosphoenolpyruvate carboxylase (PEPC), and the intracellular enzyme ferric reduction oxidase (FRO) are involved in Fe absorption. The effects of the application of citric acid (CA) and humic-like substances (HLS) on the yield, H+-ATPase, PEPC, and FRO enzyme activity, and expression of LeHA1, LePEPC1, and LeFRO1 genes in tomato plants grown under calcareous soil were studied. CA and HLS improved the SPAD units and increased the number of harvested fruits and yield per plant. Temporary alterations in enzyme activity, which reduced PEPC and FRO activity in roots, were documented. In leaf tissue, CA resulted in lower expression of LeHA1 and LePEPC1 and the induction of LeFRO1 expression, whereas HLS application resulted in higher expression of LePEPC1 and LeFRO1. In roots, LeHA1 expression increased with HLS, whereas LePEPC1 and LeFRO1 showed lower expression with CA and HLS, respectively. The application of CA and HLS through a nutrient solution in combination with Fe-chelate can improve Fe nutrition in tomato plants potted in calcareous soil by inducing temporal alterations in PEPC and FRO enzyme activity and LeFRO1 and LeHA1 gene expression.

Barley Cultivar Sarab 1 Has a Characteristic Region on the Thylakoid Membrane That Protects Photosystem I under Iron-Deficient Conditions.

The barley cultivar Sarab 1 (SRB1) can continue photosynthesis despite its low Fe acquisition potential via roots and dramatically reduced amounts of photosystem I (PSI) reaction-center proteins under Fe-deficient conditions. We compared the characteristics of photosynthetic electron transfer (ET), thylakoid ultrastructure, and Fe and protein distribution on thylakoid membranes among barley cultivars. The Fe-deficient SRB1 had a large proportion of functional PSI proteins by avoiding P700 over-reduction. An analysis of the thylakoid ultrastructure clarified that SRB1 had a larger proportion of non-appressed thylakoid membranes than those in another Fe-tolerant cultivar, Ehimehadaka-1 (EHM1). Separating thylakoids by differential centrifugation further revealed that the Fe-deficient SRB1 had increased amounts of low/light-density thylakoids with increased Fe and light-harvesting complex II (LHCII) than did EHM1. LHCII with uncommon localization probably prevents excessive ET from PSII leading to elevated NPQ and lower PSI photodamage in SRB1 than in EHM1, as supported by increased Y(NPQ) and Y(ND) in the Fe-deficient SRB1. Unlike this strategy, EHM1 may preferentially supply Fe cofactors to PSI, thereby exploiting more surplus reaction center proteins than SRB1 under Fe-deficient conditions. In summary, SRB1 and EHM1 support PSI through different mechanisms during Fe deficiency, suggesting that barley species have multiple strategies for acclimating photosynthetic apparatus to Fe deficiency.

Soybean Root Transcriptomics: Insights into Sucrose Signaling at the Crossroads of Nutrient Deficiency and Biotic Stress Responses.

Soybean (Glycine max) is an important agricultural crop, but nutrient deficiencies frequently limit soybean production. While research has advanced our understanding of plant responses to long-term nutrient deficiencies, less is known about the signaling pathways and immediate responses to certain nutrient deficiencies, such as Pi and Fe deficiencies. Recent studies have shown that sucrose acts as a long-distance signal that is sent in increased concentrations from the shoot to the root in response to various nutrient deficiencies. Here, we mimicked nutrient deficiency-induced sucrose signaling by adding sucrose directly to the roots. To unravel transcriptomic responses to sucrose acting as a signal, we performed Illumina RNA-sequencing of soybean roots treated with sucrose for 20 min and 40 min, compared to non-sucrose-treated controls. We obtained a total of 260 million paired-end reads, mapping to 61,675 soybean genes, some of which are novel (not yet annotated) transcripts. Of these, 358 genes were upregulated after 20 min, and 2416 were upregulated after 40 min of sucrose exposure. GO (gene ontology) analysis revealed a high proportion of sucrose-induced genes involved in signal transduction, particularly hormone, ROS (reactive oxygen species), and calcium signaling, in addition to regulation of transcription. In addition, GO enrichment analysis indicates that sucrose triggers crosstalk between biotic and abiotic stress responses.

Cross talk between Cu excess and Fe deficiency in the roots of rice

Copper (Cu) and iron (Fe) share similar characteristics and participate as coenzymes in several physiological processes. Both Cu excess and Fe deficiency result in chlorosis, however, the crosstalk between the two is not clear in rice. In this study, we performed transcriptome analysis for Cu excess and Fe deficiency in rice. Some WRKY family members (such as WRKY26) and some bHLH family members (such as late flowering) were selected as novel potential transcription factors involved in the regulation of Cu detoxification and Fe utilization, respectively. These genes were induced under corresponding stress conditions. Many Fe uptake-related genes were induced by Cu excess, while Cu detoxification-related genes were not induced by Fe deficiency. Meanwhile, some genes, such as metallothionein 3a, gibberellin 3beta-dioxygenase 2 and WRKY11, were induced by Cu excess but repressed by Fe deficiency. Concisely, our results highlight the crosstalk between Cu excess and Fe deficiency in rice. Cu excess caused Fe deficiency response, while Fe deficiency did not lead to Cu toxicity response. Metallothionein 3a might be responsible for Cu toxicity-induced chlorosis in rice. The crosstalk between Cu excess and Fe deficiency might be regulated by gibberellic acid.

Zinc-Sulphate and Zn-EDTA Enhances Zn and Other Nutrients and Yield and Quality of Table-Purpose Peanut Cultivars

ABSTRACT Zinc (Zn) and iron (Fe) deficiencies in humans are major problems worldwide, which necessitate their increase in food crops. Peanut (Arachis hypogaea L.), which is a good nutritional source of Zn and Fe, is used as a table-purpose food item worldwide, but is mostly grown under poor-fertility soils, resulting in low Zn concentrations in the edible seed. In a 2-year field study, the influence of zinc sulfate and Zn-EDTA, at 2 kg Zn ha−1, was studied in 20 confectionery peanut cultivars where both of these Zn sources increased yield attributes, 100-seed weight, and Zn, P, and K concentrations in seed. The respective mean concentrations of Zn, P, and K in the seed were 43 mg kg−1 and 0.61% and 0.75% in control which increased to 50 mg kg−1 and 0.62% and 0.76%, with the application of zinc sulfate and 46 mg kg−1 and 0.63% and 0.82%, respectively, with the application of Zn-EDTA. The cultivars TG 37A, GG 7, HNG 69, ICGV 00348, CSMG 884, and BAU 13 showed high protein (25% and above), Zn (>50 mg kg−1), Fe (>75 mg kg−1), P (>0.60%), and K (>0.75%) with the application of zinc sulfate and hence are being recommended for cultivation and their use as food to ameliorate micronutrient malnutrition.