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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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Fe concentration of Arabidopsis seeds.Fe was determined in the wild-type (Col-0), the nramp3/nramp4 double mutant, the vector control (GL1), the vit1-1 mutant and in seeds from the double mutant expressing one of the three VTL genes under the control of the 35S promoter. Asterisks indicate significant differences from the wild-type (p<0.01).
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pone-0110468-g005: Fe concentration of Arabidopsis seeds.Fe was determined in the wild-type (Col-0), the nramp3/nramp4 double mutant, the vector control (GL1), the vit1-1 mutant and in seeds from the double mutant expressing one of the three VTL genes under the control of the 35S promoter. Asterisks indicate significant differences from the wild-type (p<0.01).

Mentions: The proposed function of NRAMP3 and NRAMP4 was to mobilize Fe from the vacuole of young seedlings [17]. We hypothesized that over-expression of the AtVTLs might have increased total seed Fe, and thereby increased the Fe supply to the germinating seedling. To test this, we analyzed the Fe concentration in nramp3/nramp4 seeds that over-expressed the AtVTL genes. The results of these analyses demonstrated that the AtVTL1, AtVTL2 or AtVTL5 over-expressing lines had between 40 and 60% increased Fe concentration compared to either the wild type or the nramp3/nramp4 double mutant (Fig. 5; p<0.01). These results supported the concept that an increased content of Fe in the seeds could have supplied the embryo with sufficient Fe even when efflux from the vacuole through the NRAMP transporters was compromised.


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

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

Fe concentration of Arabidopsis seeds.Fe was determined in the wild-type (Col-0), the nramp3/nramp4 double mutant, the vector control (GL1), the vit1-1 mutant and in seeds from the double mutant expressing one of the three VTL genes under the control of the 35S promoter. Asterisks indicate significant differences from the wild-type (p<0.01).
© Copyright Policy
Related In: Results  -  Collection

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

pone-0110468-g005: Fe concentration of Arabidopsis seeds.Fe was determined in the wild-type (Col-0), the nramp3/nramp4 double mutant, the vector control (GL1), the vit1-1 mutant and in seeds from the double mutant expressing one of the three VTL genes under the control of the 35S promoter. Asterisks indicate significant differences from the wild-type (p<0.01).
Mentions: The proposed function of NRAMP3 and NRAMP4 was to mobilize Fe from the vacuole of young seedlings [17]. We hypothesized that over-expression of the AtVTLs might have increased total seed Fe, and thereby increased the Fe supply to the germinating seedling. To test this, we analyzed the Fe concentration in nramp3/nramp4 seeds that over-expressed the AtVTL genes. The results of these analyses demonstrated that the AtVTL1, AtVTL2 or AtVTL5 over-expressing lines had between 40 and 60% increased Fe concentration compared to either the wild type or the nramp3/nramp4 double mutant (Fig. 5; p<0.01). These results supported the concept that an increased content of Fe in the seeds could have supplied the embryo with sufficient Fe even when efflux from the vacuole through the NRAMP transporters was compromised.

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