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Source publication
We present data supporting a general role for FERRIC REDICTASE DEFECTIVE3 (FRD3), an efflux transporter of the efficient iron chelator citrate, in maintaining iron homeostasis throughout plant development. In addition to its well-known expression in root, we show that FRD3 is strongly expressed in Arabidopsis thaliana seed and flower. Consistently,...
Contexts in source publication
Context 1
... from water-irrigated frd3-7 plants showed chlorotic flower buds that fail to open at stages 12 to 13 ( Figure 5, compare D with E). As in rosette leaves of other frd3 alleles (Delhaize, 1996;Rogers and Guerinot, 2002;Lahner et al., 2003), metal content in the inflorescence of the frd3-7 mutant showed an increase in Mn and Co, as well as a decrease in iron (Table 1). When frd3-7 plants were supplemented with iron, inflorescences regreened and flowers opened ( Figure 5F). ...
Context 2
... the FRD3 gene being expressed in the sporophytic and the gametophytic tissues of the anther, we have demon- strated that the frd3 mutation acts gametophytically to affect pollen development. Indeed, heterozygous FRD3/frd3-7 plants harboring phenotypically wild-type inflorescence and anthers display ;50% of aborted pollen grains ( Figure 8F, Table 1). ...
Citations
... Zhang et al., 2019;Bashir et al., 2021). However, excessive Fe may induce toxic effects on plants because free Fe ions can be oxidatively toxic to cells where Fe is always bound to target metalloproteins or cells chelated with organic or mineral ligands (Morrissey & Guerinot, 2009;Roschzttardtz et al., 2011;Kobayashi et al., 2019), such as citrate (Rellan-Alvarez et al., 2010) and nicotianamine (NA; Schuler & Bauer, 2011); therefore, the uptake and transport of Fe throughout a plant must be precisely regulated . ...
Nicotianamine (NA) plays a crucial role in transporting metal ions, including iron (Fe), in plants; therefore, NICOTIANAMINE SYNTHASE (NAS) genes, which control NA synthesis, are tightly regulated at the transcriptional level. However, the transcriptional regulatory mechanisms of NAS genes require further investigations.
In this study, we determined the role of bZIP44 in mediating plant response to Fe deficiency stress by conducting transformation experiments and assays.
bZIP44 positively regulated the response of Arabidopsis to Fe deficiency stress by interacting with MYB10 and MYB72 to enhance their abilities to bind at NAS2 and NAS4 promoters, thereby increasing NAS2 and NAS4 transcriptional levels and promote NA synthesis.
In summary, the transcription activities of bZIP44, MYB10, and MYB72 were induced in response to Fe deficiency stress, which enhanced the interaction between bZIP44 and MYB10 or MYB72 proteins, synergistically activated the transcriptional activity of NAS2 and NAS4, promoted NA synthesis, and improved Fe transport, thereby enhancing plant tolerance to Fe deficiency stress.
... Delhaize (1996) previously reported reduced growth for the mutant genotype man1, subsequently renamed frd3-3 (Rogers and Guerinot, 2002). The FRD3 gene regulates metal (especially iron) transport from the roots to the shoot of the plant and impacts whole plant development by regulating iron transport in the xylem through citrate chelation (Durrett et al., 2007;Roschzttardtz et al., 2011). ...
Premise
Plants grown at high densities show increased tolerance to heavy metals for reasons that are not clear. A potential explanation is the release of citrate by plant roots, which binds metals and prevents uptake. Thus, pooled exudates at high plant densities might increase tolerance. We tested this exclusion facilitation hypothesis using mutants of Arabidopsis thaliana defective in citrate exudation.
Methods
Wild type Arabidopsis and two allelic mutants for the Ferric Reductase Defective 3 ( FRD3 ) gene were grown at four densities and watered with copper sulfate at four concentrations. Plants were harvested before bolting and dried. Shoot biomass was measured, and shoot material and soil were digested in nitric acid. Copper contents were determined by atomic absorption.
Results
In the highest‐copper treatment, density‐dependent reduction in toxicity was observed in the wild type but not in FRD3 mutants. For both mutants, copper concentrations per gram biomass were up to seven times higher than for wild type plants, depending on density and copper treatment. In all genotypes, total copper accumulation was greater at higher plant densities. Plant size variation increased with density and copper treatment because of heterogeneous distribution of copper throughout the soil.
Conclusions
These results support the hypothesis that citrate exudation is responsible for density‐dependent reductions in toxicity of metals. Density‐dependent copper uptake and growth in contaminated soils underscores the importance of density in ecotoxicological testing. In soils with a heterogeneous distribution of contaminants, competition for nontoxic soil regions may drive size hierarchies and determine competitive outcomes.
... As a result of their chelation property, cellular OA secretion is a common adaptation to a range of mineral deficiencies and aluminium toxicity in plants (Gherardi & Rengel, 2004;Hoffland et al., 1989;Jones, 1998;Mart ınez-Cuenca et al., 2013;Wang et al., 2007). This secretion can occur either at the root-soil interface, in the xylem or the apoplast via membrane-localized OA transporters (Carvalhais et al., 2011;Durrett et al., 2007;Roschzttardtz et al., 2011). OA transporters of the multidrug and toxic compound extrusion (MATE) and Al-activated malate transporter (ALMT) families are known to assist the uptake and homeostasis of minerals. ...
... MATE family members usually transport citrate (Pereira & Ryan, 2019). For instance, Arabidopsis (Arabidopsis thaliana) FERRIC REDUCTASE DEFECTIVE 3 (FRD3) is involved in citrate efflux, which is required for Fe translocation through xylem and apoplastic spaces (Durrett et al., 2007;Rogers & Guerinot, 2002;Roschzttardtz et al., 2011). Similar functions were observed for citrate transporters of other species, like FERRIC REDUCTASE DEFECTIVE LIKE 1 (OsFRDL1) in rice and ScFRDL1 in rye (Yokosho et al., 2009(Yokosho et al., , 2010. ...
... Plant citrate transporters are expressed in various tissues for different functions. For instance, in Arabidopsis, FRD3 is highly expressed in root, seed and flowering tissues (Rogers & Guerinot, 2002;Roschzttardtz et al., 2011) while rice FRDL1 is expressed in root pericycle cells for citrate loading in the xylem (Yokosho et al., 2009;Yokosho, Yamaji, & Ma, 2016). Other MATE family transporters such as OsFRDL4, OsFRDL2, ScFRDL2 and HvAACT1 are expressed in root epidermal cells for citrate exudation under aluminium toxicity (Yokosho et al., 2010;Yokosho et al., 2011;Yokosho et al., 2016b;Zhou et al., 2013). ...
The plant citrate transporters, functional in mineral nutrient uptake and homeostasis, usually belong to the
multidrug and toxic compound extrusion transporter family. We identified and functionally characterized a
rice (Oryza sativa) citrate transporter, OsCT1, which differs from known plant citrate transporters and is
structurally close to rice silicon transporters. Domain analysis depicted that OsCT1 carries a bacterial
citrate-metal transporter domain, CitMHS. OsCT1 showed citrate efflux activity when expressed in Xenopus
laevis oocytes and is localized to the cell plasma membrane. It is highly expressed in the shoot and reproductive
tissues of rice, and its promoter activity was visible in cells surrounding the vasculature. The OsCT1
knockout (KO) lines showed a reduced citrate content in the shoots and the root exudates, whereas overexpression
(OE) line showed higher citrate exudation from their roots. Further, the KO and OE lines showed
variations in the manganese (Mn) distribution leading to changes in their agronomical traits. Under deficient
conditions (Mn-sufficient conditions followed by 8 days of 0 lM MnCl2 � 4H2O treatment), the supply of manganese
towards the newer leaf was found to be obstructed in the KO line. There were no significant differences
in phosphorus (P) distribution; however, P uptake was reduced in the KO and increased in OE lines at
the vegetative stage. Further, experiments in Xenopus oocytes revealed that OsCT1 could efflux citrate with
Mn. In this way, we provide insights into a mechanism of citrate-metal transport in plants and its role in
mineral homeostasis, which remains conserved with their bacterial counterparts.
... Briefly, the pollen grains were placed on the slides with forceps, and the anthers were extruded and exposed to 1% (v/v) I 2 -KI solution for 5 min at room temperature for full staining. The stained pollens were then observed and photographed under the bright-field illumination of the microscope (Roschzttardtz et al., 2011;Yokosho et al., 2016). There are three types of pollen viability: fertile with full stain (black), fertile with partial stain (brown), and sterile (yellow or transparent). ...
... We found that the pollen viability and grain fertility were reduced in the knockdown lines compared to WT in a paddy field ( Fig. 6B and G), suggesting that OsNRAMP7 is vital for pollen maturation and seed development. Fe is an essential trace element for pollen development (Roschzttardtz et al., 2011;Huang and Suen, 2021), due to Fe homeostasis in reproductive tissues is vital to support Fe-dependent protein function in these tissues (Huang and Suen, 2021). The reproductive tissues receiving Fe from the soil or some source tissues like mature leaf blade. ...
Iron (Fe) is an essential micronutrient for plant growth and human health. Plants have evolved an efficient transport system for absorbing and redistributing Fe from the soil to other organs; however, the molecular mechanisms underlying Fe loading into grains are poorly understood. Our study shows that OsNRAMP7, a member of the natural resistance-associated macrophage protein (NRAMP) family, is a rice Fe transporter that localizes to the Golgi and trans-Golgi network (TGN). OsNRAMP7 was highly expressed in leaf blade, node I, pollen, and vascular tissues of almost tissues at the rice flowering stage. OsNRAMP7 knockdown by RNA interference (RNAi) increased Fe accumulation in the flag leaf blade, but decreased the Fe concentration in node I and rice grains. In addition, the knockdown of OsNRAMP7 also reduced grain fertility, pollen viability, and grain Fe concentration in the paddy fields; OsNRAMP7 overexpression significantly promoted Fe accumulation in the grains. Thus, our results suggest that OsNRAMP7 is required for the distribution and accumulation of Fe in rice grains and its overexpression could be a novel strategy for Fe biofortification in staple food crops.
... As the plant enters the reproductive stage, nodules senesce (Puppo et al., 2005;Van de Velde et al., 2006). Considering the prevalent low metal bioavailability in soils (Chen & Barak, 1982;Alloway, 2008), the large amounts used in nodules (Johnston et al., 2001), and the importance of transition metals for seed production and germination (Sancenon et al., 2004;Kim et al., 2006;Roschzttardtz et al., 2011), a large portion of the nodule metal content should be recycled. It is estimated that around half of the nodule iron is relocalized to the seeds when nodules senesce (Burton et al., 1998), and a similar recovery of other limiting transition elements can be expected. ...
Symbiotic nitrogen fixation carried out by the interaction between legumes and rhizobia is the main source of nitrogen in natural ecosystems and in sustainable agriculture. For the symbiosis to be viable, nutrient exchange between the partners is essential. Transition metals are among the nutrients delivered to the nitrogen‐fixing bacteria within the legume root nodule cells. These elements are used as cofactors for many of the enzymes controlling nodule development and function, including nitrogenase, the only known enzyme able to convert N2 into NH3. In this review, we discuss the current knowledge on how iron, zinc, copper, and molybdenum reach the nodules, how they are delivered to nodule cells, and how they are transferred to nitrogen‐fixing bacteria within.
... For the translocation of Fe-citrate complex in apoplast, FRD3 and OsFRDL1 genes play a role that is essential for floral tissue development in Arabidopsis (Roschzttardtz et al., 2011) and rice plant (Yokosho et al., 2016a,b). ...
... Mutations in the FRD3 gene provoked the interruption of Fe transport between tapetum and pollen cells, abortion of developing pollen grains and ultimately the sterility of the frd3 mutant flowers. 4 The last illustration of the metal requirements was related to the fecundation of the ovule by the pollen grain. When pollen grains reach the female part of flowers (stigma) they germinate and develop a pollen tube that will grow from the stigma down to the ovary to reach the ovule and deliver the male nuclei. ...
The acquisition and storage of essential metals (Fe, Cu, Zn, Mn…) is considered to be crucial for the quality of pollen grains. It is therefore strategic to develop analytical approaches...
... Once absorbed into the root epidermal cells, Fe is radially transported to the vasculature via the symplastic pathway and then extruded from the parenchyma cells inside the stele into the xylem vessels in the form of Fe(II), possibly via the ferroportin (FPN)-like protein FPN1 (Morrissey et al., 2009). In addition, efflux of citrate into the xylem via the multidrug and toxin efflux family member FRD3 plays a crucial role in the xylem transport of Fe (Rogers and Guerinot, 2002;Green and Rogers, 2004;Durrett et al., 2007;Roschzttardtz et al., 2011). Iron is transported in the xylem vessels to the above-ground organs in the form of Fe(III)-citrate or Fe(III)-citrate-malate complexes (Durrett et al., 2007;Flis et al., 2016;von Wiré n et al., 1999), implying an oxidation step of Fe(II) to Fe(III) (Gayomba et al., 2015). ...
... The phenotypes of lpr1 lpr2 mutant are to a certain extent similar to those of the frd3 mutant defective in the export of citrate to the xylem, including chlorosis, constitutive expression of Fe deficiency responses, overaccumulation of Fe and other divalent transition metals, and deposition of Fe in the xylem vessels (Rogers and Guerinot, 2002;Green and Rogers, 2004;Durrett et al., 2007;Roschzttardtz et al., 2011), although the chlorosis phenotype of lpr1 lpr2 is less severe than those of frd3 under normal Fe supply. The similarities point to the importance of maintaining Fe as Fe(III)-citrate/malate during xylem translocation. ...
Iron (Fe) deficiency is common in agricultural crops and affects millions of people worldwide. Translocation of Fe in the xylem is a key step for Fe distribution in plants. The mechanism controlling this process remains largely unknown. Here, we report that two Arabidopsis ferroxidases, LPR1 and LPR2, play a crucial and redundant role in controlling Fe translocation in the xylem. LPR1 and LPR2 are mainly localized in the cell walls of xylem vessels and the surrounding cells in roots, leaves and stems. Knockout of both LPR1 and LPR2 increased the proportion of Fe(II) in the xylem sap, and caused Fe deposition along the vascular bundles especially in the petioles and main veins of leaves, which was alleviated by blocking blue light. The double mutant displayed constitutive expression of Fe-deficiency response genes and overaccumulation of Fe in the roots and mature leaves under Fe-sufficient supply, but Fe-deficiency chlorosis in the new leaves and inflorescences under low Fe supply. The double mutant showed lower Fe concentrations in the xylem and phloem saps and impaired ⁵⁷Fe translocation along the xylem. In vitro assays showed that Fe(III)-citrate, the main form of Fe in xylem sap, is easily photoreduced to Fe(II)-citrate, which is unstable and prone to adsorption by cell walls. Taken together, these results indicate that LPR1 and LPR2 are required to oxidize Fe(II) and maintain Fe(III)-citrate stability and mobility during xylem translocation against photoreduction. This study not only uncovers an essential physiological role of LPR1 and LPR2 but also reveals a new mechanism by which plants maintain Fe mobility during long-distance translocation in the xylem.
... Inside the plant system, Fe is only mobilized with the help of chelators (nicotianamine, deoxymugineic acid, and citrate), secreted by the nicotianamine efflux transporters (Nozoye et al., 2011). Although citrate along with the ferric reductase defective 3 (FRD3) enzyme family predominantly transports Fe in the xylem for most of the plant genera (Roschzttardtz et al., 2011), OsFRDL1 knockout mutant of rice, however, does not reduce the Fe concentration in xylem fluid. However, the concentration of Fe 2+ in the xylem sap is higher and the concentration of Fe 3+ is lower in mutant plants than normal (Yokosho et al., 2009). ...
... Moreover, the mechanism of xylem unloading and subsequent phloem loading lacks well documentation. However, recent reports highlighted the involvement of OsIRT1, OsIRT2, and OsNRAMP1 in phloem loading via transporters of YSL family (Aoyama et al., 2009;Kobayashi et al., 2014) and direct xylem loading by Fe-citrate complex via an unidentified transport system (Roschzttardtz et al., 2011). ...
Rice is the third largest crop produced worldwide, the majority of which is flood irrigated and accounts for about one-third of the global irrigated area. Relative to other crops, rice requires a large amount of scarce water input. Research has shown that irrigated rice water use can be substantially reduced by decreasing the period of permanent flooding through water saving irrigation techniques. For regions where irrigation water can be controlled, increased labour demand, weed and pest infestation and risk of water stress are major inhibiting factors for widescale adoption of water saving rice. Automation of irrigation has the potential to resolve some of these issues. Automated irrigation has long been commercially practised in pressurized systems and proven to save significant labor; however, it has not been adopted in gravity surface irrigation systems.
The purpose of this chapter is to review the current status of automated gravity surface irrigation in rice, identify potential technical adoption-limiting factors of the few previously developed systems and outline additional functionality required of an automated irrigation system for water savings in commercial scale rice systems during both ponded and non-ponded periods. To harness the full economic, social and environmental benefits that automation could provide, research is required to determine the most appropriate parameters to schedule irrigation during non-ponded periods and regionally and varietal specific thresholds. Resolution of the research and technical gaps outlined in this chapter could enable widescale adoption of irrigation practice that significantly reduce irrigation water input whilst simultaneously reducing paddy GHG emissions.
... Sensing of iron deficiency in the root vasculature leads to a series of physiological responses in the root epidermis that result in iron uptake from the rhizosphere. After uptake into epidermal cells, iron is likely bound to the nonproteinogenic amino acid, nicotianamine (NA) (Hell and Stephan, 2003), and transported through the epidermis, cortex, and endodermis to the pericycle and other living vascular cells before being effluxed into the xylem and chelated to citrate for long distance transport from the root to the shoot (Roschzttardtz et al., 2011). The outer layer of the vasculature, the pericycle, is the most transcriptionally active group of cells in the root under iron starvation (Dinneny et al., 2008) and it is particularly enriched in transcription factors that are responsive to iron deficiency (Long et al., 2010). ...
Plants must tightly regulate iron (Fe) sensing, acquisition, transport, mobilization, and storage to ensure sufficient levels of this essential micronutrient. POPEYE (PYE) is an iron responsive transcription factor that positively regulates the iron deficiency response, while also repressing genes essential for maintaining iron homeostasis. However, little is known about how PYE plays such contradictory roles. Under iron-deficient conditions pPYE:GFP accumulates in the root pericycle while pPYE:PYE-GFP is localized to the nucleus in all Arabidopsis (Arabidopsis thaliana) root cells, suggesting that PYE may have cell-specific dynamics and functions. Using scanning fluorescence correlation spectroscopy (scanning FCS) and cell-specific promoters, we found that PYE-GFP moves between different cells and that the tendency for movement corresponds with transcript abundance. While localization to the cortex, endodermis, and vasculature is required to manage changes in iron availability, vasculature and endodermis localization of PYE-GFP protein exacerbated pye-1 defects and elicited a host of transcriptional changes that are detrimental to iron mobilization. Our findings indicate that PYE acts as a positive regulator of iron deficiency response by regulating iron bioavailability differentially across cells, which may trigger iron uptake from the surrounding rhizosphere and impact root energy metabolism.
