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Vacuolar-Iron-Transporter1-Like proteins mediate iron homeostasis in Arabidopsis.

Gollhofer J, Timofeev R, Lan P, Schmidt W, Buckhout TJ - PLoS ONE (2014)

Bottom Line: Isolated vacuoles from yeast expressing either of the VTL genes in the Δccc1 background had a three- to four-fold increase in Fe concentration compared to vacuoles isolated from the untransformed mutant.Seedling root growth of the Arabidopsis nramp3/nramp4 and vit1-1 mutants was decreased compared to the wild type when seedlings were grown under Fe deficiency.We conclude that the VTL proteins catalyze Fe transport into vacuoles and thus contribute to the regulation of Fe homeostasis in planta.

View Article: PubMed Central - PubMed

Affiliation: Institute of Biology, Humboldt University Berlin, Berlin, Germany.

ABSTRACT
Iron deficiency is a nutritional problem in plants and reduces crop productivity, quality and yield. With the goal of improving the iron (Fe) storage properties of plants, we have investigated the function of three Arabidopsis proteins with homology to Vacuolar Iron Transporter1 (AtVIT1). Heterologous expression of Vacuolar Iron Transporter-Like1 (AtVTL1; At1g21140), AtVTL2 (At1g76800) or AtVTL5 (At3g25190) in the yeast vacuolar Fe transport mutant, Δccc1, restored growth in the presence of 4 mM Fe. Isolated vacuoles from yeast expressing either of the VTL genes in the Δccc1 background had a three- to four-fold increase in Fe concentration compared to vacuoles isolated from the untransformed mutant. Transiently expressed GFP-tagged AtVTL1 was localized exclusively and AtVTL2 was localized primarily to the vacuolar membrane of onion epidermis cells. Seedling root growth of the Arabidopsis nramp3/nramp4 and vit1-1 mutants was decreased compared to the wild type when seedlings were grown under Fe deficiency. When expressed under the 35S promoter in the nramp3/nramp4 or vit1-1 backgrounds, AtVTL1, AtVTL2 or AtVTL5 restored root growth in both mutants. The seed Fe concentration in the nramp3/nramp4 mutant overexpressing AtVTL1, AtVTL2 or AtVTL5 was between 50 and 60% higher than in non-transformed double mutants or wild-type plants. We conclude that the VTL proteins catalyze Fe transport into vacuoles and thus contribute to the regulation of Fe homeostasis in planta.

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Complementation of the vit1-1 mutant by over-expression of AtVTL1, AtVTL2 or AtVTL5.The three VTL genes were over-expressed under the control of the 35S promoter in the vit1-1 background. Root length was determined after 13 days of growth on agarose Petri plates as described in the Materials and Methods ion ES medium without added Fe and in the presence of the Fe2+ chelator, Ferrozine. Asterisks indicate significant differences from the wild-type (p<0.001). Shown are results from 2 independent transformants.
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pone-0110468-g006: Complementation of the vit1-1 mutant by over-expression of AtVTL1, AtVTL2 or AtVTL5.The three VTL genes were over-expressed under the control of the 35S promoter in the vit1-1 background. Root length was determined after 13 days of growth on agarose Petri plates as described in the Materials and Methods ion ES medium without added Fe and in the presence of the Fe2+ chelator, Ferrozine. Asterisks indicate significant differences from the wild-type (p<0.001). Shown are results from 2 independent transformants.

Mentions: As mentioned above, the CCC1-like protein, AtVIT1, is localized on the vacuolar membrane and functions in the transport of Fe into the parenchyma cell of the provascular strands in developing embryos. The vit1-1 mutant showed misdistribution of Fe; although, vit1-1 mutant seeds had unchanged Fe content compared to the wild type (Fig. 5) [16]. vit1-1 had a severely chlorotic phenotype when grown on alkaline soil [16]. In addition, we observed that vit1-1 displayed a short-root phenotype similar to the nramp3/nramp4 mutant when grown on Fe-deficient media in the presence of the Fe2+ chelator Ferrozine (Fig. 6 and Fig. S6). Over-expression of AtVTL1, AtVTL2 or AtVTL5 restored root growth to greater than the wild-type length (p>0.001), thus complementing the vit1-1 mutation.


Vacuolar-Iron-Transporter1-Like proteins mediate iron homeostasis in Arabidopsis.

Gollhofer J, Timofeev R, Lan P, Schmidt W, Buckhout TJ - PLoS ONE (2014)

Complementation of the vit1-1 mutant by over-expression of AtVTL1, AtVTL2 or AtVTL5.The three VTL genes were over-expressed under the control of the 35S promoter in the vit1-1 background. Root length was determined after 13 days of growth on agarose Petri plates as described in the Materials and Methods ion ES medium without added Fe and in the presence of the Fe2+ chelator, Ferrozine. Asterisks indicate significant differences from the wild-type (p<0.001). Shown are results from 2 independent transformants.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4215979&req=5

pone-0110468-g006: Complementation of the vit1-1 mutant by over-expression of AtVTL1, AtVTL2 or AtVTL5.The three VTL genes were over-expressed under the control of the 35S promoter in the vit1-1 background. Root length was determined after 13 days of growth on agarose Petri plates as described in the Materials and Methods ion ES medium without added Fe and in the presence of the Fe2+ chelator, Ferrozine. Asterisks indicate significant differences from the wild-type (p<0.001). Shown are results from 2 independent transformants.
Mentions: As mentioned above, the CCC1-like protein, AtVIT1, is localized on the vacuolar membrane and functions in the transport of Fe into the parenchyma cell of the provascular strands in developing embryos. The vit1-1 mutant showed misdistribution of Fe; although, vit1-1 mutant seeds had unchanged Fe content compared to the wild type (Fig. 5) [16]. vit1-1 had a severely chlorotic phenotype when grown on alkaline soil [16]. In addition, we observed that vit1-1 displayed a short-root phenotype similar to the nramp3/nramp4 mutant when grown on Fe-deficient media in the presence of the Fe2+ chelator Ferrozine (Fig. 6 and Fig. S6). Over-expression of AtVTL1, AtVTL2 or AtVTL5 restored root growth to greater than the wild-type length (p>0.001), thus complementing the vit1-1 mutation.

Bottom Line: Isolated vacuoles from yeast expressing either of the VTL genes in the Δccc1 background had a three- to four-fold increase in Fe concentration compared to vacuoles isolated from the untransformed mutant.Seedling root growth of the Arabidopsis nramp3/nramp4 and vit1-1 mutants was decreased compared to the wild type when seedlings were grown under Fe deficiency.We conclude that the VTL proteins catalyze Fe transport into vacuoles and thus contribute to the regulation of Fe homeostasis in planta.

View Article: PubMed Central - PubMed

Affiliation: Institute of Biology, Humboldt University Berlin, Berlin, Germany.

ABSTRACT
Iron deficiency is a nutritional problem in plants and reduces crop productivity, quality and yield. With the goal of improving the iron (Fe) storage properties of plants, we have investigated the function of three Arabidopsis proteins with homology to Vacuolar Iron Transporter1 (AtVIT1). Heterologous expression of Vacuolar Iron Transporter-Like1 (AtVTL1; At1g21140), AtVTL2 (At1g76800) or AtVTL5 (At3g25190) in the yeast vacuolar Fe transport mutant, Δccc1, restored growth in the presence of 4 mM Fe. Isolated vacuoles from yeast expressing either of the VTL genes in the Δccc1 background had a three- to four-fold increase in Fe concentration compared to vacuoles isolated from the untransformed mutant. Transiently expressed GFP-tagged AtVTL1 was localized exclusively and AtVTL2 was localized primarily to the vacuolar membrane of onion epidermis cells. Seedling root growth of the Arabidopsis nramp3/nramp4 and vit1-1 mutants was decreased compared to the wild type when seedlings were grown under Fe deficiency. When expressed under the 35S promoter in the nramp3/nramp4 or vit1-1 backgrounds, AtVTL1, AtVTL2 or AtVTL5 restored root growth in both mutants. The seed Fe concentration in the nramp3/nramp4 mutant overexpressing AtVTL1, AtVTL2 or AtVTL5 was between 50 and 60% higher than in non-transformed double mutants or wild-type plants. We conclude that the VTL proteins catalyze Fe transport into vacuoles and thus contribute to the regulation of Fe homeostasis in planta.

Show MeSH
Related in: MedlinePlus