Aluminium-induced inhibition of root elongation in Arabidopsis is mediated by ethylene and auxin.
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.
State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing, P.R. China.
Pei
P
Sun
Qiu-Ying
QY
Tian
Jie
J
Chen
Wen-Hao
WH
Zhang
D000077410:Aluminum Chloride; D017607:Aluminum Compounds / Q000633:toxicity*; D017360:Arabidopsis / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D002712:Chlorides / Q000633:toxicity*; D005030:Ethylenes / Q000378:metabolism*; D007210:Indoleacetic Acids / Q000378:metabolism*; D018517:Plant Roots / Q000187:drug effects / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects
D017607:Aluminum Compounds; D029681:Arabidopsis Proteins; D002712:Chlorides; D005030:Ethylenes; D007210:Indoleacetic Acids; D000077410:Aluminum Chloride; C036216:ethylene