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Acquisition of aluminium tolerance by modification of a single gene in barley.

Fujii M, Yokosho K, Yamaji N, Saisho D, Yamane M, Takahashi H, Sato K, Nakazono M, Ma JF - Nat Commun (2012)

Bottom Line: We find that the primary function of this protein is to release citrate from the root pericycle cells to the xylem to facilitate the translocation of iron from roots to shoots.The altered HvAACT1 has an important role in detoxifying aluminium by secreting citrate to the rhizosphere.Thus, the insertion of a 1-kb sequence in the HvAACT1 upstream enables barley to adapt to acidic soils.

View Article: PubMed Central - PubMed

Affiliation: Institute of Plant Science and Resources, Okayama University, Kurashiki 710-0046, Japan.

ABSTRACT
Originating from the Fertile Crescent in the Middle East, barley has now been cultivated widely on different soil types including acid soils, where aluminium toxicity is a major limiting factor. Here we show that the adaptation of barley to acid soils is achieved by the modification of a single gene (HvAACT1) encoding a citrate transporter. We find that the primary function of this protein is to release citrate from the root pericycle cells to the xylem to facilitate the translocation of iron from roots to shoots. However, a 1-kb insertion in the upstream of the HvAACT1 coding region occurring only in the Al-tolerant accessions, enhances its expression and alters the location of expression to the root tips. The altered HvAACT1 has an important role in detoxifying aluminium by secreting citrate to the rhizosphere. Thus, the insertion of a 1-kb sequence in the HvAACT1 upstream enables barley to adapt to acidic soils.

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Complementation test for iron translocation in rice.(a) Rescue of leaf chlorosis by the introduction of Morex HvAACT1. (b,c) SPAD value of the youngest expanded leaf of transgenic rice carrying Morex-type HvAACT1 promoter grown in a nutrient solution containing 0.2 (b) or 10 (c) μM FeSO4. Data are shown as means±s.d. (n=4–6). (d,e) Concentration of citrate (d) and iron (e) in the xylem sap of different rice lines. (f,g) Concentration of iron in the shoots (f) and roots (g). Data are shown as means±s.d. (n=3–5). Statistical comparison was performed by one-way ANOVA followed by Dunnett's multiple comparison test. *P<0.05. All data were compared with osfrdl1. (h) Rescue of iron precipitation in the roots by the introduction of Morex HvAACT1. Scale bars in a and h indicate 10 mm and 100 μm, respectively.
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f5: Complementation test for iron translocation in rice.(a) Rescue of leaf chlorosis by the introduction of Morex HvAACT1. (b,c) SPAD value of the youngest expanded leaf of transgenic rice carrying Morex-type HvAACT1 promoter grown in a nutrient solution containing 0.2 (b) or 10 (c) μM FeSO4. Data are shown as means±s.d. (n=4–6). (d,e) Concentration of citrate (d) and iron (e) in the xylem sap of different rice lines. (f,g) Concentration of iron in the shoots (f) and roots (g). Data are shown as means±s.d. (n=3–5). Statistical comparison was performed by one-way ANOVA followed by Dunnett's multiple comparison test. *P<0.05. All data were compared with osfrdl1. (h) Rescue of iron precipitation in the roots by the introduction of Morex HvAACT1. Scale bars in a and h indicate 10 mm and 100 μm, respectively.

Mentions: The similar expression level of HvAACT1 in the central cylinder tissues of the mature root zone of both cultivars suggests that HvAACT1 has other functions (Fig. 3g). HvAACT1 is a homologue of OsFRDL1 in rice and AtFRD3 in Arabidopsis2122, which are localized in the pericycle cells and involved in the translocation of iron from the roots to the shoots by transporting citrate into the xylem. To test whether HvAACT1 is also involved in iron translocation, we introduced the Morex-type HvAACT1 into the rice mutant osfrdl1 defective in the translocation of iron21. When the mutant was grown at a low Fe concentration (0.2 μM), the new leaves of osfrdl1 mutant showed chlorosis typical of Fe deficiency (Fig. 5a), whereas the transgenic lines carrying HvAACT1 rescued the phenotype of the mutant. The SPAD (indicator of chlorophyll content) value of the youngest expanded leaf was lower in the osfrdl1 mutant than the wild-type rice; this was restored to the wild-type level by the transformation with HvAACT1 (Fig. 5b). In the presence of high Fe (10 μM), all lines showed similar SPAD values (Fig. 5c).


Acquisition of aluminium tolerance by modification of a single gene in barley.

Fujii M, Yokosho K, Yamaji N, Saisho D, Yamane M, Takahashi H, Sato K, Nakazono M, Ma JF - Nat Commun (2012)

Complementation test for iron translocation in rice.(a) Rescue of leaf chlorosis by the introduction of Morex HvAACT1. (b,c) SPAD value of the youngest expanded leaf of transgenic rice carrying Morex-type HvAACT1 promoter grown in a nutrient solution containing 0.2 (b) or 10 (c) μM FeSO4. Data are shown as means±s.d. (n=4–6). (d,e) Concentration of citrate (d) and iron (e) in the xylem sap of different rice lines. (f,g) Concentration of iron in the shoots (f) and roots (g). Data are shown as means±s.d. (n=3–5). Statistical comparison was performed by one-way ANOVA followed by Dunnett's multiple comparison test. *P<0.05. All data were compared with osfrdl1. (h) Rescue of iron precipitation in the roots by the introduction of Morex HvAACT1. Scale bars in a and h indicate 10 mm and 100 μm, respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3316887&req=5

f5: Complementation test for iron translocation in rice.(a) Rescue of leaf chlorosis by the introduction of Morex HvAACT1. (b,c) SPAD value of the youngest expanded leaf of transgenic rice carrying Morex-type HvAACT1 promoter grown in a nutrient solution containing 0.2 (b) or 10 (c) μM FeSO4. Data are shown as means±s.d. (n=4–6). (d,e) Concentration of citrate (d) and iron (e) in the xylem sap of different rice lines. (f,g) Concentration of iron in the shoots (f) and roots (g). Data are shown as means±s.d. (n=3–5). Statistical comparison was performed by one-way ANOVA followed by Dunnett's multiple comparison test. *P<0.05. All data were compared with osfrdl1. (h) Rescue of iron precipitation in the roots by the introduction of Morex HvAACT1. Scale bars in a and h indicate 10 mm and 100 μm, respectively.
Mentions: The similar expression level of HvAACT1 in the central cylinder tissues of the mature root zone of both cultivars suggests that HvAACT1 has other functions (Fig. 3g). HvAACT1 is a homologue of OsFRDL1 in rice and AtFRD3 in Arabidopsis2122, which are localized in the pericycle cells and involved in the translocation of iron from the roots to the shoots by transporting citrate into the xylem. To test whether HvAACT1 is also involved in iron translocation, we introduced the Morex-type HvAACT1 into the rice mutant osfrdl1 defective in the translocation of iron21. When the mutant was grown at a low Fe concentration (0.2 μM), the new leaves of osfrdl1 mutant showed chlorosis typical of Fe deficiency (Fig. 5a), whereas the transgenic lines carrying HvAACT1 rescued the phenotype of the mutant. The SPAD (indicator of chlorophyll content) value of the youngest expanded leaf was lower in the osfrdl1 mutant than the wild-type rice; this was restored to the wild-type level by the transformation with HvAACT1 (Fig. 5b). In the presence of high Fe (10 μM), all lines showed similar SPAD values (Fig. 5c).

Bottom Line: We find that the primary function of this protein is to release citrate from the root pericycle cells to the xylem to facilitate the translocation of iron from roots to shoots.The altered HvAACT1 has an important role in detoxifying aluminium by secreting citrate to the rhizosphere.Thus, the insertion of a 1-kb sequence in the HvAACT1 upstream enables barley to adapt to acidic soils.

View Article: PubMed Central - PubMed

Affiliation: Institute of Plant Science and Resources, Okayama University, Kurashiki 710-0046, Japan.

ABSTRACT
Originating from the Fertile Crescent in the Middle East, barley has now been cultivated widely on different soil types including acid soils, where aluminium toxicity is a major limiting factor. Here we show that the adaptation of barley to acid soils is achieved by the modification of a single gene (HvAACT1) encoding a citrate transporter. We find that the primary function of this protein is to release citrate from the root pericycle cells to the xylem to facilitate the translocation of iron from roots to shoots. However, a 1-kb insertion in the upstream of the HvAACT1 coding region occurring only in the Al-tolerant accessions, enhances its expression and alters the location of expression to the root tips. The altered HvAACT1 has an important role in detoxifying aluminium by secreting citrate to the rhizosphere. Thus, the insertion of a 1-kb sequence in the HvAACT1 upstream enables barley to adapt to acidic soils.

Show MeSH
Related in: MedlinePlus