skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


  • NSF Public Access
  • Search Results
  • OPT3 plays a central role in both copper and iron homeostasis and signaling due to its 2 ability to deliver copper as well as iron to the phloem in Arabidopsis
Title: OPT3 plays a central role in both copper and iron homeostasis and signaling due to its 2 ability to deliver copper as well as iron to the phloem in Arabidopsis
Copper and iron are micronutrients but are toxic when they accumulate in cells in excess. Crosstalk between copper and iron homeostasis in Arabidopsis thaliana has been documented and includes iron accumulation under copper deficiency and vice versa. However, molecular components of this crosstalk are not well understood. Iron concentration in the phloem has been suggested to act systemically, negatively regulating iron uptake to the root. Consistently, systemic iron signaling is disrupted in A. thaliana mutants lacking the phloem companion cell-localized iron transporter, AtOPT3, and opt3 mutants hyperaccumulate iron. Here, we report that in addition to iron, AtOPT3 transports copper and mediates copper loading to the phloem for delivery from sources to sinks. As a result of this function, the opt3-3 mutant accumulates less copper in the phloem, roots, developing leaves and embryos compared to wild type, is sensitive to copper deficiency, and mounts transcriptional copper deficiency response. Because copper deficiency has been shown to stimulate iron accumulation, we propose that reduced copper concentration in the phloem of the opt3-3 mutant and its constitutive copper deficiency contribute to iron overaccumulation in its tissues. Our data assign new transport capabilities to AtOPT3 and increase understanding of copper - iron interactions and signaling.  more » « less
Award ID(s):
1754966
PAR ID:
10285492
Author(s) / Creator(s):
Date Published:
Journal Name:
bioRxiv
ISSN:
2692-8205
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ; ; ; ; ; ; ; et al (, The Plant Cell)
    Abstract Copper (Cu) and iron (Fe) are essential micronutrients that are toxic when accumulating in excess in cells. Thus, their uptake by roots is tightly regulated. While plants sense and respond to local Cu availability, the systemic regulation of Cu uptake has not been documented in contrast to local and systemic control of Fe uptake. Fe abundance in the phloem has been suggested to act systemically, regulating the expression of Fe uptake genes in roots. Consistently, shoot-to-root Fe signaling is disrupted in Arabidopsis thaliana mutants lacking the phloem companion cell-localized Fe transporter, OLIGOPEPTIDE TRANSPORTER 3 (AtOPT3). We report that AtOPT3 also transports Cu in heterologous systems and contributes to its delivery from sources to sinks in planta. The opt3 mutant contained less Cu in the phloem, was sensitive to Cu deficiency and mounted a transcriptional Cu deficiency response in roots and young leaves. Feeding the opt3 mutant and Cu- or Fe-deficient wild-type seedlings with Cu or Fe via the phloem in leaves downregulated the expression of both Cu- and Fe-deficiency marker genes in roots. These data suggest the existence of shoot-to-root Cu signaling, highlight the complexity of Cu/Fe interactions, and the role of AtOPT3 in fine-tuning root transcriptional responses to the plant Cu and Fe needs. 
    more » « less
  2. ; ; (, Plants)
    NA (Ed.)
    In order to discover sRNA that might function during iron deficiency stress, RNA was prepared from phloem exudates of Arabidopsis thaliana, and used for RNA-seq. Bioanalyzer results indicate that abundant RNA from phloem is small in size—less than 200 nt. Moreover, typical rRNA bands were not observed. Sequencing of eight independent phloem RNA samples indicated that tRNA-derived fragments, specifically 5′ tRFs and 5′ tRNA halves, are highly abundant in phloem sap, comprising about 46% of all reads. In addition, a set of miRNAs that are present in phloem sap was defined, and several miRNAs and sRNAs were identified that are differentially expressed during iron deficiency. 
    more » « less
  3. ; ; ; ; ; ; ; (, Plant and Cell Physiology)
    Abstract Iron (Fe) uptake and translocation in plants are fine-tuned by complex mechanisms that are not yet fully understood. In Arabidopsis thaliana, local regulation of Fe homeostasis at the root level has been extensively studied and is better understood than the systemic shoot-to-root regulation. While the root system is solely a sink tissue that depends on photosynthates translocated from source tissues, the shoot system is a more complex tissue, where sink and source tissues occur synchronously. In this study, and to gain better insight into the Fe deficiency responses in leaves, we overexpressed Zinc/Iron-regulated transporter-like Protein (ZIP5), an Fe/Zn transporter, in phloem-loading cells (proSUC2::AtZIP5) and determined the timing of Fe deficiency responses in sink (young leaves and roots) and source tissues (leaves). Transgenic lines overexpressing ZIP5 in companion cells displayed increased sensitivity to Fe deficiency in root growth assays. Moreover, young leaves and roots (sink tissues) displayed either delayed or dampened transcriptional responses to Fe deficiency compared to wild-type (WT) plants. We also took advantage of the Arabidopsis mutant nas4x-1 to explore Fe transcriptional responses in the opposite scenario, where Fe is retained in the vasculature but in an unavailable and precipitated form. In contrast to proSUC2::AtZIP5 plants, nas4x-1 young leaves and roots displayed a robust and constitutive Fe deficiency response, while mature leaves showed a delayed and dampened Fe deficiency response compared to WT plants. Altogether, our data provide evidence suggesting that Fe sensing within leaves can also occur locally in a leaf-specific manner. 
    more » « less
  4. ; (, Frontiers in Plant Science)
    Long non-coding RNAs (lncRNAs) are RNA molecules with functions independent of any protein-coding potential. A whole transcriptome (RNA-seq) study of Arabidopsis shoots under iron sufficient and deficient conditions was carried out to determine the genes that are iron-regulated in the shoots. We identified two previously unannotated transcripts on chromosome 1 that are significantly iron-regulated. We have called this iron-regulated lncRNA, CAN OF SPINACH ( COS ). cos mutants have altered iron levels in leaves and seeds. Despite the low iron levels in the leaves, cos mutants have higher chlorophyll levels than WT plants. Moreover, cos mutants have abnormal development during iron deficiency. Roots of cos mutants are longer than those of WT plants, when grown on iron deficient medium. In addition, cos mutant plants accumulate singlet oxygen during iron deficiency. The mechanism through which COS affects iron deficiency responses is unclear, but small regions of sequence similarity to several genes involved in iron deficiency responses occur in COS , and small RNAs from these regions have been detected. We hypothesize that COS is required for normal adaptation to iron deficiency conditions. 
    more » « less
  5. ; ; ; (, bioRxiv)
    Abstract Strigolactones are plant hormones with roles in a wide range of signaling and developmental processes. A yellow-striped maize mutant, (interveinalyellow)ivy, was determined to have low iron in tissues under normal growth conditions. The gene underlying theivymutation was mapped and identified asZmCCD8, a key enzyme in the biosynthesis of strigolactones. Under iron-replete conditions, comparison of the transcriptomes of wild-type plants and maizeccd8mutants revealed suppression of several iron-regulated genes inccd8. These genes are normally up-regulated during iron deficiency and include the key iron-regulated transcription factorIRO2as well as genes involved in the biosynthesis of iron chelators and transporters. External supply of synthetic strigolactone toivymutants alleviated chlorosis and returned iron-regulated gene expression to wild-type levels. In iron limited conditions, iron-regulated gene expression inccd8mutants responded normally, indicating that strigolactones are not required for response to externally imposed iron deficiency. However, they are required for basal expression of iron-regulated genes when adequate iron is available, highlighting a distinction between iron homeostasis during normal growth, and the iron deficiency response triggered by the lack of external available iron. The connection between strigolactones and iron homeostasis is not limited to maize, as Arabidopsisccd8mutants also show strong chlorosis when grown on medium with moderate levels of iron. This previously unappreciated role may have implications for the use of strigolactones in agricultural contexts. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email