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Aluminium-induced inhibition of root elongation in Arabidopsis is mediated by ethylene and auxin.

Sun P, Tian QY, Chen J, Zhang WH - J. Exp. Bot. (2009)

Bottom Line: The Al(3+)-induced increase in DR5:GUS activity was reduced by AVG, while the Al(3+)-induced increase in EBS:GUS activity was not altered by NPA.Al(3+) and ACC increased transcripts of AUX1 and PIN2, and this effect was no longer observed in the presence of AVG and Co(2+).These findings indicate that Al(3+)-induced ethylene production is likely to act as a signal to alter auxin distribution in roots by disrupting AUX1- and PIN2-mediated auxin polar transport, leading to arrest of root elongation.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing, P.R. China.

ABSTRACT
Aluminium (Al) is phytotoxic when solubilized into Al(3+) in acidic soils. One of the earliest and distinct symptoms of Al(3+) toxicity is inhibition of root elongation. To decipher the mechanism by which Al(3+) inhibits root elongation, the role of ethylene and auxin in Al(3+)-induced inhibition of root elongation in Arabidopsis thaliana was investigated using the wild type and mutants defective in ethylene signalling (etr1-3 and ein2-1) and auxin polar transport (aux1-7 and pin2). Exposure of wild-type Arabidopsis to AlCl(3) led to a marked inhibition of root elongation, and elicited a rapid ethylene evolution and enhanced activity of the ethylene reporter EBS:GUS in root apices. Root elongation in etr1-3 and ein2-1 mutants was less inhibited by Al(3+) than that in wild-type plants. Ethylene synthesis inhibitors, Co(2+) and aminoethoxyvinylglycine (AVG), and an antagonist of ethylene perception (Ag(+)) abolished the Al(3+)-induced inhibition of root elongation. There was less inhibition of root elongation by Al(3+) in aux1-7 and pin2 mutants than in the wild type. The auxin polar transport inhibitor, naphthylphthalamic acid (NPA), substantially alleviated the Al(3+)-induced inhibition of root elongation. The Al(3+) and ethylene synthesis precursor aminocyclopropane carboxylic acid (ACC) increased auxin reporter DR5:GUS activity in roots. The Al(3+)-induced increase in DR5:GUS activity was reduced by AVG, while the Al(3+)-induced increase in EBS:GUS activity was not altered by NPA. Al(3+) and ACC increased transcripts of AUX1 and PIN2, and this effect was no longer observed in the presence of AVG and Co(2+). These findings indicate that Al(3+)-induced ethylene production is likely to act as a signal to alter auxin distribution in roots by disrupting AUX1- and PIN2-mediated auxin polar transport, leading to arrest of root elongation.

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Effect of AlCl3 on root elongation of Arabidopsis wild-type (Col-0) and auxin polar transport mutants, aux1-7 and pin2. (A) Seedlings of Col-0, aux1-7, and pin2 were exposed to 50 μM AlCl3 (pH 4.5) and root length was measured under a stereomicroscope after 24 h. (B) Effect of AlCl3 on root elongation of seedlings grown on agar medium containing varying concentrations of AlCl3 (pH 4.5) for 4 d. Data are expressed as relative root elongation relative to controls, and are presented as means ±SE of >8 roots. The root elongation rate in the absence of AlCl3 for Col-0, aux1-7, and pin2 was 5.41±0.13 mm d−1 (n=17), 7.14±0.47 mm d−1 (n=13), and 5.26±0.11 mm d−1 (n=10), respectively.
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fig3: Effect of AlCl3 on root elongation of Arabidopsis wild-type (Col-0) and auxin polar transport mutants, aux1-7 and pin2. (A) Seedlings of Col-0, aux1-7, and pin2 were exposed to 50 μM AlCl3 (pH 4.5) and root length was measured under a stereomicroscope after 24 h. (B) Effect of AlCl3 on root elongation of seedlings grown on agar medium containing varying concentrations of AlCl3 (pH 4.5) for 4 d. Data are expressed as relative root elongation relative to controls, and are presented as means ±SE of >8 roots. The root elongation rate in the absence of AlCl3 for Col-0, aux1-7, and pin2 was 5.41±0.13 mm d−1 (n=17), 7.14±0.47 mm d−1 (n=13), and 5.26±0.11 mm d−1 (n=10), respectively.

Mentions: In addition to ethylene, the role of auxin in Al-induced inhibition of root elongation was also examined using the auxin polar transport mutants aux1-7 and pin2. In contrast to wild-type plants, root elongation in both aux1-7 and pin2 was relatively insensitive to Al3+ when treated with 50 μM Al3+ hydroponically for 24 h (Fig. 3A). When both wild-type and mutant seedlings were grown in agar containing varying concentrations of AlCl3 for 4 d, root elongation of aux1-7 and pin2 was also less inhibited than that of the wild type (Fig. 3B). For instance, root elongation in wild-type plants was reduced by 38% when grown in agar containing 100 μM AlCl3 (pH 4.5), while root elongation in aux1-7 and pin2 was not affected when grown under the identical AlCl3 conditions (Fig. 3B). These results are indicative that AUX1 and PIN2 are involved in Al-induced inhibition of root elongation in Arabidopsis.


Aluminium-induced inhibition of root elongation in Arabidopsis is mediated by ethylene and auxin.

Sun P, Tian QY, Chen J, Zhang WH - J. Exp. Bot. (2009)

Effect of AlCl3 on root elongation of Arabidopsis wild-type (Col-0) and auxin polar transport mutants, aux1-7 and pin2. (A) Seedlings of Col-0, aux1-7, and pin2 were exposed to 50 μM AlCl3 (pH 4.5) and root length was measured under a stereomicroscope after 24 h. (B) Effect of AlCl3 on root elongation of seedlings grown on agar medium containing varying concentrations of AlCl3 (pH 4.5) for 4 d. Data are expressed as relative root elongation relative to controls, and are presented as means ±SE of >8 roots. The root elongation rate in the absence of AlCl3 for Col-0, aux1-7, and pin2 was 5.41±0.13 mm d−1 (n=17), 7.14±0.47 mm d−1 (n=13), and 5.26±0.11 mm d−1 (n=10), respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2803203&req=5

fig3: Effect of AlCl3 on root elongation of Arabidopsis wild-type (Col-0) and auxin polar transport mutants, aux1-7 and pin2. (A) Seedlings of Col-0, aux1-7, and pin2 were exposed to 50 μM AlCl3 (pH 4.5) and root length was measured under a stereomicroscope after 24 h. (B) Effect of AlCl3 on root elongation of seedlings grown on agar medium containing varying concentrations of AlCl3 (pH 4.5) for 4 d. Data are expressed as relative root elongation relative to controls, and are presented as means ±SE of >8 roots. The root elongation rate in the absence of AlCl3 for Col-0, aux1-7, and pin2 was 5.41±0.13 mm d−1 (n=17), 7.14±0.47 mm d−1 (n=13), and 5.26±0.11 mm d−1 (n=10), respectively.
Mentions: In addition to ethylene, the role of auxin in Al-induced inhibition of root elongation was also examined using the auxin polar transport mutants aux1-7 and pin2. In contrast to wild-type plants, root elongation in both aux1-7 and pin2 was relatively insensitive to Al3+ when treated with 50 μM Al3+ hydroponically for 24 h (Fig. 3A). When both wild-type and mutant seedlings were grown in agar containing varying concentrations of AlCl3 for 4 d, root elongation of aux1-7 and pin2 was also less inhibited than that of the wild type (Fig. 3B). For instance, root elongation in wild-type plants was reduced by 38% when grown in agar containing 100 μM AlCl3 (pH 4.5), while root elongation in aux1-7 and pin2 was not affected when grown under the identical AlCl3 conditions (Fig. 3B). These results are indicative that AUX1 and PIN2 are involved in Al-induced inhibition of root elongation in Arabidopsis.

Bottom Line: The Al(3+)-induced increase in DR5:GUS activity was reduced by AVG, while the Al(3+)-induced increase in EBS:GUS activity was not altered by NPA.Al(3+) and ACC increased transcripts of AUX1 and PIN2, and this effect was no longer observed in the presence of AVG and Co(2+).These findings indicate that Al(3+)-induced ethylene production is likely to act as a signal to alter auxin distribution in roots by disrupting AUX1- and PIN2-mediated auxin polar transport, leading to arrest of root elongation.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing, P.R. China.

ABSTRACT
Aluminium (Al) is phytotoxic when solubilized into Al(3+) in acidic soils. One of the earliest and distinct symptoms of Al(3+) toxicity is inhibition of root elongation. To decipher the mechanism by which Al(3+) inhibits root elongation, the role of ethylene and auxin in Al(3+)-induced inhibition of root elongation in Arabidopsis thaliana was investigated using the wild type and mutants defective in ethylene signalling (etr1-3 and ein2-1) and auxin polar transport (aux1-7 and pin2). Exposure of wild-type Arabidopsis to AlCl(3) led to a marked inhibition of root elongation, and elicited a rapid ethylene evolution and enhanced activity of the ethylene reporter EBS:GUS in root apices. Root elongation in etr1-3 and ein2-1 mutants was less inhibited by Al(3+) than that in wild-type plants. Ethylene synthesis inhibitors, Co(2+) and aminoethoxyvinylglycine (AVG), and an antagonist of ethylene perception (Ag(+)) abolished the Al(3+)-induced inhibition of root elongation. There was less inhibition of root elongation by Al(3+) in aux1-7 and pin2 mutants than in the wild type. The auxin polar transport inhibitor, naphthylphthalamic acid (NPA), substantially alleviated the Al(3+)-induced inhibition of root elongation. The Al(3+) and ethylene synthesis precursor aminocyclopropane carboxylic acid (ACC) increased auxin reporter DR5:GUS activity in roots. The Al(3+)-induced increase in DR5:GUS activity was reduced by AVG, while the Al(3+)-induced increase in EBS:GUS activity was not altered by NPA. Al(3+) and ACC increased transcripts of AUX1 and PIN2, and this effect was no longer observed in the presence of AVG and Co(2+). These findings indicate that Al(3+)-induced ethylene production is likely to act as a signal to alter auxin distribution in roots by disrupting AUX1- and PIN2-mediated auxin polar transport, leading to arrest of root elongation.

Show MeSH
Related in: MedlinePlus