Dynamic interactions between SPX proteins, the ubiquitination machinery, and signalling molecules for stress adaptation at a whole-plant level.

The plant macronutrient phosphorus is a scarce resource and plant-available phosphate is limiting in most soil types. Generally, a gene regulatory module called the phosphate starvation response (PSR) enables efficient phosphate acquisition by roots and translocation to other organs. Plants growing on moderate to nutrient-rich soils need to co-ordinate availability of different nutrients and repress the highly efficient PSR to adjust phosphate acquisition to the availability of other macro- and micronutrients, and in particular nitrogen. PSR repression is mediated by a small family of single SYG1/Pho81/XPR1 (SPX) domain proteins. The SPX domain binds higher order inositol pyrophosphates that signal cellular phosphorus status and modulate SPX protein interaction with PHOSPHATE STARVATION RESPONSE1 (PHR1), the central transcriptional regulator of PSR. Sequestration by SPX repressors restricts PHR1 access to PSR gene promoters. Here we focus on SPX4 that primarily acts in shoots and sequesters many transcription factors other than PHR1 in the cytosol to control processes beyond the classical PSR, such as nitrate, auxin, and jasmonic acid signalling. Unlike SPX1 and SPX2, SPX4 is subject to proteasomal degradation not only by singular E3 ligases, but also by SCF-CRL complexes. Emerging models for these different layers of control and their consequences for plant acclimation to the environment will be discussed.

OPEN leaf: an open-source cloud-based phenotyping system for tracking dynamic changes at leaf-specific resolution in Arabidopsis.

The first draft of the Arabidopsis genome was released more than 20 years ago and despite intensive molecular research, more than 30% of Arabidopsis genes remained uncharacterized or without an assigned function. This is in part due to gene redundancy within gene families or the essential nature of genes, where their deletion results in lethality (i.e., the dark genome). High-throughput plant phenotyping (HTPP) offers an automated and unbiased approach to characterize subtle or transient phenotypes resulting from gene redundancy or inducible gene silencing; however, access to commercial HTPP platforms remains limited. Here we describe the design and implementation of OPEN leaf, an open-source phenotyping system with cloud connectivity and remote bilateral communication to facilitate data collection, sharing and processing. OPEN leaf, coupled with our SMART imaging processing pipeline was able to consistently document and quantify dynamic changes at the whole rosette level and leaf-specific resolution when plants experienced changes in nutrient availability. Our data also demonstrate that VIS sensors remain underutilized and can be used in high-throughput screens to identify and characterize previously unidentified phenotypes in a leaf-specific time-dependent manner. Moreover, the modular and open-source design of OPEN leaf allows seamless integration of additional sensors based on users and experimental needs.

Optimizing nutrient solution for vegetative growth of Dendrobium Tubtim Siam and Phalaenopsis Taisuco Swan through plant tissue nutrient balance estimation.

BACKGROUND: Orchids are grown without soil in many regions of the world, but there is a lack of studies to define the balanced and adequate nutrient solution for their cultivation, mainly in the vegetative growth phase. Therefore, this paper aims to evaluate the optimal concentration of the nutrient solution based on the proposal by Hoagland and Arnon (1950) in the vegetative growth phase capable of increasing the nutrient contents, growth, and dry matter production of Dendrobium Tubtim Siam and Phalaenopsis Taisuco Swan. In addition, this paper aims to estimate a new nutrient solution from the optimal nutrient contents in the dry matter of these orchid species to be used in the vegetative growth phase. RESULTS: Nutrient contents, growth, and dry matter production increased as the nutrient solution concentration increased up to an average concentration of 62 and 77% for D. Tubtim Siam and P. Taisuco Swan, respectively. We found that the Hoagland and Arnon solution presented a group of nutrients with concentrations above the requirement for P. Taisuco Swan (nitrogen, phosphor, calcium, and sulfur) and D. Tubtim Siam (phosphor, calcium, magnesium, and sulfur), while other nutrients in the solution did not meet the nutritional demand of these orchid species, inducing nutritional imbalance in the vegetative growth phase. CONCLUSION: We conclude that using a balanced nutrient solution created specifically for each orchid species in vegetative growth might favor their sustainable cultivation by optimizing the use of nutrients in the growing medium.

Transcriptional and metabolic profiling of sulfur starvation response in two monocots.

BACKGROUND: Sulfur (S) is a mineral nutrient essential for plant growth and development, which is incorporated into diverse molecules fundamental for primary and secondary metabolism, plant defense, signaling, and maintaining cellular homeostasis. Although, S starvation response is well documented in the dicot model Arabidopsis thaliana, it is not clear if the same transcriptional networks control the response also in the monocots. RESULTS: We performed series of physiological, expression, and metabolite analyses in two model monocot species, one representing the C3 plants, Oryza sativa cv. kitaake, and second representing the C4 plants, Setaria viridis. Our comprehensive transcriptomic analysis revealed twice as many differentially expressed genes (DEGs) in S. viridis than in O. sativa under S-deficiency, consistent with a greater loss of sulfur and S-containing metabolites under these conditions. Surprisingly, most of the DEGs and enriched gene ontology terms were species-specific, with an intersect of only 58 common DEGs. The transcriptional networks were different in roots and shoots of both species, in particular no genes were down-regulated by S-deficiency in the roots of both species. CONCLUSIONS: Our analysis shows that S-deficiency seems to have different physiological consequences in the two monocot species and their nutrient homeostasis might be under distinct control mechanisms.

Rhizosphere priming promotes plant nitrogen acquisition by microbial necromass recycling.

Nitrogen availability in the rhizosphere relies on root-microorganism interactions, where root exudates trigger soil organic matter (SOM) decomposition through the rhizosphere priming effect (RPE). Though microbial necromass contribute significantly to organically bound soil nitrogen (N), the role of RPEs in regulating necromass recycling and plant nitrogen acquisition has received limited attention. We used 15N natural abundance as a proxy for necromass-N since necromass is enriched in 15N compared to other soil-N forms. We combined studies using the same experimental design for continuous 13CO2 labelling of various plant species and the same soil type, but considering top- and subsoil. RPE were quantified as difference in SOM-decomposition between planted and unplanted soils. Results showed higher plant N uptake as RPEs increased. The positive relationship between 15N-enrichment of shoots and roots and RPEs indicated an enhanced necromass-N turnover by RPE. Moreover, our data revealed that RPEs were saturated with increasing carbon (C) input via rhizodeposition in topsoil. In subsoil, RPEs increased linearly within a small range of C input indicating a strong effect of root-released C on decomposition rates in deeper soil horizons. Overall, this study confirmed the functional importance of rhizosphere C input for plant N acquisition through enhanced necromass turnover by RPEs.

Plant-soil synchrony in nutrient cycles: Learning from ecosystems to design sustainable agrosystems.

Redesigning agrosystems to include more ecological regulations can help feed a growing human population, preserve soils for future productivity, limit dependency on synthetic fertilizers, and reduce agriculture contribution to global changes such as eutrophication and warming. However, guidelines for redesigning cropping systems from natural systems to make them more sustainable remain limited. Synthetizing the knowledge on biogeochemical cycles in natural ecosystems, we outline four ecological systems that synchronize the supply of soluble nutrients by soil biota with the fluctuating nutrient demand of plants. This synchrony limits deficiencies and excesses of soluble nutrients, which usually penalize both production and regulating services of agrosystems such as nutrient retention and soil carbon storage. In the ecological systems outlined, synchrony emerges from plant-soil and plant-plant interactions, eco-physiological processes, soil physicochemical processes, and the dynamics of various nutrient reservoirs, including soil organic matter, soil minerals, atmosphere, and a common market. We discuss the relative importance of these ecological systems in regulating nutrient cycles depending on the pedoclimatic context and on the functional diversity of plants and microbes. We offer ideas about how these systems could be stimulated within agrosystems to improve their sustainability. A review of the latest advances in agronomy shows that some of the practices suggested to promote synchrony (e.g., reduced tillage, rotation with perennial plant cover, crop diversification) have already been tested and shown to be effective in reducing nutrient losses, fertilizer use, and N2 O emissions and/or improving biomass production and soil carbon storage. Our framework also highlights new management strategies and defines the conditions for the success of these nature-based practices allowing for site-specific modifications. This new synthetized knowledge should help practitioners to improve the long-term productivity of agrosystems while reducing the negative impact of agriculture on the environment and the climate.

New insights into the role of the root system of epiphytic bromeliads: comparison of root and leaf trichome functions in acquisition of water and nutrients.

BACKGROUND: In epiphytic bromeliads, the roots used to be considered poorly functional organs in the processes of absorption and metabolization of water and nutrients, while the leaves always acted as protagonists in both functions. More recent discoveries have been changing this old view of the root system. SCOPE: In this review, we will address the old thoughts of the scientific community regarding the function performed by the roots of epiphytic bromeliads (mere holdfast structures with low physiological activity) and the importance of a reduced or lack of root system for the emergence of epiphytism. We will present indirect and direct evidence that contradicts this older hypothesis. Furthermore, the importance of the root absorptive function mainly for juvenile tankless epiphytic bromeliads and the characteristics of the root absorption process of adult epiphytic tank bromeliads will be thoroughly discussed in physiological aspects. Finally, some factors (species, substrate, environmental conditions) that influence the absorptive capability of the roots of epiphytic tank bromeliads will also be considered in this review, highlighting the importance that the absorptive role of the roots have for the plasticity of bromeliads that live on trees, which is an environment characterized by the intermittent availability of water and nutrients. CONCLUSIONS: The roots of tank-forming epiphytic bromeliads play important roles in the absorption and metabolization of nutrients and water. The importance of roots stands out mainly for juvenile tankless bromeliads since the root is the main absorptive organ. In larger plants with tank, although the leaves become the protagonists in the resource acquisition process, the roots complement the absorptive function of the leaf trichomes, resulting in a better growth of the bromeliad. The physiological and biochemical properties of the processes of absorption and distribution of resources in the tissues seem to differ between absorption by trichomes and roots.

Arbuscular mycorrhizal symbiosis with Rhizophagus irregularis DAOM197198 modifies the root transcriptome of walnut trees.

Walnut trees are cultivated and exploited worldwide for commercial timber and nut production. They are heterografted plants, with the rootstock selected to grow in different soil types and conditions and to provide the best anchorage, vigor, and resistance or tolerance to soil borne pests and diseases. However, no individual rootstock is tolerant of all factors that impact walnut production. In Europe, Juglans regia is mainly used as a rootstock. Like most terrestrial plants, walnut trees form arbuscular mycorrhizal symbioses, improving water and nutrient uptake and providing additional ecosystem services. Effects of arbuscular mycorrhizal symbiosis on root gene regulation, however, has never been assessed. We analyzed the response of one rootstock of J. regia to colonization by the arbuscular mycorrhizal fungus Rhizophagus irregularis DAOM197198. Plant growth as well as the nitrogen and phosphorus concentrations in roots and shoots were significantly increased in mycorrhizal plants versus non-colonized plants. In addition, we have shown that 1,549 genes were differentially expressed, with 832 and 717 genes up- and down-regulated, respectively. The analysis also revealed that some rootstock genes involved in plant nutrition through the mycorrhizal pathway, are regulated similarly as in other mycorrhizal woody species: Vitis vinifera and Populus trichocarpa. In addition, an enrichment analysis performed on GO and KEGG pathways revealed some regulation specific to J. regia (i.e., the juglone pathway). This analysis reinforces the role of arbuscular mycorrhizal symbiosis on root gene regulation and on the need to finely study the effects of diverse arbuscular mycorrhizal fungi on root gene regulation, but also of the scion on the functioning of an arbuscular mycorrhizal fungus in heterografted plants such as walnut tree.

Divergent colonization traits, convergent benefits: different species of arbuscular mycorrhizal fungi alleviate Meloidogyne incognita damage in tomato.

Arbuscular mycorrhizal fungi (AMF) can increase plant tolerance and/or resistance to pests such as the root-knot nematode Meloidogyne incognita. However, the ameliorative effects may depend on AMF species. The aim of this work was therefore to evaluate whether four AMF species differentially affect plant performance in response to M. incognita infection. Tomato plants grown in greenhouse conditions were inoculated with four different AMF isolates (Claroideoglomus claroideum, Funneliformis mosseae, Gigaspora margarita, and Rhizophagus intraradices) and infected with 100 second stage juveniles of M. incognita at two different times: simultaneously or 2 weeks after the inoculation with AMF. After 60 days, the number of galls, egg masses, and reproduction factor of the nematodes were assessed along with plant biomass, phosphorus (P), and nitrogen concentrations in roots and shoots and root colonization by AMF. Only the simultaneous nematode inoculation without AMF caused a large reduction in plant shoot biomass, while all AMF species were able to ameliorate this effect and improve plant P uptake. The AMF isolates responded differently to the interaction with nematodes, either increasing the frequency of vesicles (C. claroideum) or reducing the number of arbuscules (F. mosseae and Gi. margarita). AMF inoculation did not decrease galls; however, it reduced the number of egg masses per gall in nematode simultaneous inoculation, except for C. claroideum. This work shows the importance of biotic stress alleviation associated with an improvement in P uptake and mediated by four different AMF species, irrespective of their fungal root colonization levels and specific interactions with the parasite.

Occurrence of Arbuscular Mycorrhizal Herbs Decreases Selectively in Communities Dominated by Invasive Tree Acer negundo.

We tested whether one of the consequences predicted for alien plant invasion by the mutualism disruption hypothesis was true in the case of the ash-leaved maple Acer negundo L. The study aimed to determine whether the occurrences of mycorrhizal and nonmycorrhizal herbs varied similarly or differently in communities with varying degrees of A. negundo dominance. The analysis included the results of 78 vegetation descriptions carried out in Belarusian Polesia, the Middle Volga region, and the Middle Urals. Communities with or without A. negundo dominance were described in each region. The mycorrhizal status of plant species was determined using the FungalRoot Database. Species that are more likely to form arbuscular mycorrhiza were found to occur less frequently in A. negundo thickets. On the contrary, a higher probability of the nonmycorrhizal status was associated with a lower frequency of detection in A. negundo thickets. Therefore, the occurrence of arbuscular mycorrhizal herbs was found to selectively decrease in communities dominated by A. negundo.

Localization and circulation: vesicle trafficking in regulating plant nutrient homeostasis.

Nutrient homeostasis is essential for plant growth and reproduction. Plants, therefore, have evolved tightly regulated mechanisms for the uptake, translocation, distribution, and storage of mineral nutrients. Considering that inorganic nutrient transport relies on membrane-based transporters and channels, vesicle trafficking, one of the fundamental cell biological processes, has become a hotspot of plant nutrition studies. In this review, we summarize recent advances in the study of how vesicle trafficking regulates nutrient homeostasis to contribute to the adaptation of plants to heterogeneous environments. We also discuss new perspectives on future studies, which may inspire researchers to investigate new approaches to improve the human diet and health by changing the nutrient quality of crops.

Sculpting the soil microbiota.

Soil is a living ecosystem, the health of which depends on fine interactions among its abiotic and biotic components. These form a delicate equilibrium maintained through a multilayer network that absorbs certain perturbations and guarantees soil functioning. Deciphering the principles governing the interactions within soils is of critical importance for their management and conservation. Here, we focus on soil microbiota and discuss the complexity of interactions that impact the composition and function of soil microbiota and their interaction with plants. We discuss how physical aspects of soils influence microbiota composition and how microbiota-plant interactions support plant growth and responses to nutrient deficiencies. We predict that understanding the principles determining the configuration and functioning of soil microbiota will contribute to the design of microbiota-based strategies to preserve natural resources and develop more environmentally friendly agricultural practices.

Unique features of regulation of sulfate assimilation in monocots.

Sulfate assimilation is an essential pathway of plant primary metabolism, regulated by the demand for reduced sulfur (S). The S-containing tripeptide glutathione (GSH) is the key signal for such regulation in Arabidopsis, but little is known about the conservation of these regulatory mechanisms beyond this model species. Using two model monocot species, C3 rice (Oryza sativa) and C4Setaria viridis, and feeding of cysteine or GSH, we aimed to find out how conserved are the regulatory mechanisms described for Arabidopsis in these species. We showed that while in principle the regulation is similar, there are many species-specific differences. For example, thiols supplied by the roots are translocated to the shoots in rice but remain in the roots of Setaria. Cysteine and GSH concentrations are highly correlated in Setaria, but not in rice. In both rice and Setaria, GSH seems to be the signal for demand-driven regulation of sulfate assimilation. Unexpectedly, we observed cysteine oxidation to sulfate in both species, a reaction that does not occur in Arabidopsis. This reaction is dependent on sulfite oxidase, but the enzyme(s) releasing sulfite from cysteine still need to be identified. Altogether our data reveal a number of unique features in the regulation of S metabolism in the monocot species and indicate the need for using multiple taxonomically distinct models to better understand the control of nutrient homeostasis, which is important for generating low-input crop varieties.

Sulfur oxidizing bacteria in agro ecosystem and its role in plant productivity-a review.

Sulfur (S) deficiency is becoming more common in agro-ecosystems worldwide due to factors such as agronomic practices, high biomass production, reduced sulfur emissions, and the use of non-sulfur fertilizers. This review explores the natural occurrence and commercial exploitation of sulfur pools in nature, the mineralization and immobilization of sulfur, the physiological role of sulfur in plants, and its deficiency symptoms. Additionally, the organic and inorganic forms of sulfur in soil, their transformations, and the process of microbiological oxidation of sulfur are discussed. The review also addresses the diversity of sulfur-oxidizing bacteria (SOB) and the various biochemical mechanisms involved in their role in plant productivity and soil reclamation. The measurement of S oxidation rate in soil and the variables that influence the process are also examined. Typically, the rate of oxidation of added elemental S is around 40%-51%, which is available for plant uptake. These characteristics of SOB demonstrate their potential as bioinoculants for increasing plant growth, indicating their use as biofertilizers for sustainable crop production in agro-ecosystems.

How to Increase the Nutritional Quality of Stinging Nettle Through Controlled Plant Nutrition§.

Research background: As food production faces major challenges, modern agricultural practices are increasingly focused on conserving resources, reducing negative environmental impacts and sustainably producing food with a high content of health-promoting phytochemicals. During production, many factors can affect the quality and chemical composition of a final food product. Proper selection of cultivating conditions, especially a balanced nutrition, can significantly increase nutritional value and result in foods with strong biological and functional properties. Stinging nettle is a rich source of minerals, vitamins, pigments, phenols and other bioactive compounds and can be consumed as a green leafy vegetable with beneficial effects on human health. Therefore, the aim of this study is to determine the nutritional quality and antioxidant capacity of stinging nettle leaves under the influence of different nutrient solution (NS) treatments and three harvest cycles. Experimental approach: The experiment was conducted in a floating hydroponic system in which treatments with different nutrient solutions were applied and three harvest cycles were carried out. After each harvest, the following treatments were applied: treatment 1 - depletion of nutrient solution by adding water, treatment 2 - supplementation of nutrient solution by adding initial nutrient solution and treatment 3 - correction of nutrient solution by adding nutrients. Among the bioactive compounds, minerals, ascorbic acid, phenols and photosynthetic pigments content, as well as antioxidant capacity were analysed spectrophotometrically, while individual phenols were determined by liquid chromatography. Results and conclusions: Different nutrition solution treatments and the number of harvest cycles had a significant effect on the content of the analysed bioactive compounds. The highest mass fraction (on fresh mass basis) of total phenols expressed as gallic acid equivalents (377.04 mg/100 g), total flavonoids expressed as catechol equivalents (279.54 mg/100 g), ascorbic acid (112.37 mg/100 g) and pigments (total chlorophylls 1.84, and total carotenoids 0.36 mg/g) as well as the highest antioxidant capacity expressed as Trolox equivalents (35.47 µmol/g) were recorded in the samples supplemented with nutrient solution (treatment NS2) and analysed after the third harvest. Novelty and scientific contribution: This is the first time that stinging nettle leaves have been produced in a floating hydroponic system by controlled plant nutrition. We have set this type of nutritional manipulation with multiple harvest cycles as an innovative technique for the production of novel food with improved nutritional value that can be consumed as green leafy vegetables.

Arabidopsis Glucan Synthase-Like1 (GSL1) Is Required for Tolerance to Low-Calcium Conditions and Exhibits a Function Comparable to GSL10.

Crops that exhibit symptoms of calcium (Ca) deficiency constitute a major agricultural problem. Molecular breeding of resistant cultivars is a promising method for overcoming this problem. However, the involved genes must first be identified. Here, we show that the glucan synthase-like (GSL) 1 gene is essential for low-Ca tolerance in Arabidopsis thaliana. GSL1 is homologous to GSL10, which we previously showed was essential for low-Ca tolerance. Under low-Ca conditions, gsl1 mutants exhibit reduced growth and the onset of necrosis in new leaves. These symptoms are typical of Ca-deficient crops. A grafting experiment suggested that the shoot genotype, but not the root genotype, was important for the suppression of shoot necrosis. The ectopic accumulation of callose under low-Ca conditions was significantly reduced in gsl1 mutants compared with wild-type plants. Because the corresponding single-mutant phenotypes are similar, we investigated the interaction between GSL1 and GSL10 by testing the gsl1 gsl10 double mutant for sensitivity to low-Ca conditions. The double mutant exhibited a more severe phenotype than did the single mutants, indicating that the effects of GSL1 and GSL10 on low-Ca tolerance are additive. Because GSL genes are highly conserved within the plant kingdom, the GSL loci may be useful for breeding low-Ca tolerant crops.

Regulatory long non-coding RNAs in root growth and development.

As sessile organisms, plants have evolved sophisticated mechanisms of gene regulation to cope with changing environments. Among them, long non-coding RNAs (lncRNAs) are a class of RNAs regulating gene expression at both transcriptional and post-transcriptional levels. They are highly responsive to environmental cues or developmental processes and are generally involved in fine-tuning plant responses to these signals. Roots, in addition to anchoring the plant to the soil, allow it to absorb the major part of its mineral nutrients and water. Furthermore, roots directly sense environmental constraints such as mineral nutrient availability and abiotic or biotic stresses and dynamically adapt their growth and architecture. Here, we review the role of lncRNAs in the control of root growth and development. In particular, we highlight their action in fine-tuning primary root growth and the development of root lateral organs, such as lateral roots and symbiotic nodules. Lastly, we report their involvement in plant response to stresses and the regulation of nutrient assimilation and homeostasis, two processes leading to the modification of root architecture. LncRNAs could become interesting targets in plant breeding programs to subtly acclimate crops to coming environmental changes.

The fine-tuning of mycorrhizal pathway in sorghum depends on both nitrogen-phosphorus availability and the identity of the fungal partner.

Sorghum is an important worldwide source of food, feed and fibres. Like most plants, it forms mutualistic symbioses with arbuscular mycorrhizal fungi (AMF), but the nutritional basis of mycorrhiza-responsiveness is largely unknown. Here, we investigated the transcriptional and physiological responses of sorghum to two different AMF species, Rhizophagus irregularis and Funneliformis mosseae, under 16 different conditions of nitrogen (N) and phosphorus (P) supply. Our experiment reveals fine-scale differences between two AMF species in the nutritional interactions with sorghum plants. Physiological and gene expression patterns (ammonium transporters: AMT; phosphate transporters: PHT) indicate the existence of generalist or specialist mycorrhizal pathway. While R. irregularis switched on the mycorrhizal pathway independently of the plant nutritional status, F. mosseae influenced the mycorrhizal pathway depending on the N-to-P plant ratio and soil supply. The differences between both AMF species suggest some AMT and PHT as ideal candidates to develop markers for improving efficiency of nutrient acquisition in sorghum under P and N limitation, and for the selection of plant genotypes.

New aspects of the photodegradation of iron(III) citrate: spectroscopic studies and plant-related factors.

Iron (Fe) is an essential cofactor for all livings. Although Fe membrane transport mechanisms often utilize FeII, uncoordinated or deliberated ferrous ions can initiate Fenton reactions. FeIII citrate complexes are among the most important complexed forms of FeIII especially in plants that, indeed, can undergo photoreduction. Since leaves as photosynthetic organs of higher plants are generally exposed to illumination in daytime, photoreaction of ferric species may have biological relevance in iron metabolism, the relevance of which is poorly understood. In present work FeIII citrate transformation during the photodegradation in solution and after foliar application on leaves was studied by Mössbauer analysis directly. To obtain irradiation time dependence of the speciation of iron in solutions, four model solutions of different pH values (1.5, 3.3, 5.5, and 7.0) with Fe to citrate molar ratio 1:1.1 were exposed to light. Highly acidic conditions led to a complete reduction of Fe together with the formation of FeII citrate and hexaaqua complexes in equal concentration. At higher pH, the only product of the photodegradation was FeII citrate, which was later reoxidized and polymerized, resulting in the formation of polynuclear stable ferric compound. To test biological relevance, leaves of cabbage were treated with FeIII citrate solution. X-ray fluorescence imaging indicated the accumulation of Fe in the treated leaf parts. Mössbauer analysis revealed the presence of several ferric species incorporated into the biological structure. The Fe speciation observed should be considered in biological systems where FeIII citrate has a ubiquitous role in Fe acquisition and homeostasis.

Mutagenesis analysis of GMN motif in Arabidopsis thaliana Mg2+ transporter MRS2-1.

Magnesium is an important nutrient for plants, but much is still unknown about plant Mg2+ transporters. Combining with the structural prediction of AlphaFold2, we used mutagenesis and 28Mg uptake assay to study the highly conserved "GMN" motif of Arabidopsis thaliana MRS2-1 (AtMRS2-1) transporter. We demonstrated that the glycine and methionine in GMN motif are essential for AtMRS2-1 to transport Mg2+.