Differential activation of genes related to aluminium tolerance in two contrasting rice cultivars.
Rice (Oryza sativa) is a highly Al-tolerant crop. Among other mechanisms, a higher expression of STAR1/STAR2 (sensitive to Al rhizotoxicity1/2) genes and of Nrat1 (NRAMP Aluminium Transporter 1), and ALS1 (Aluminium sensitive 1) can at least in part be responsible for the inducible Al tolerance in this species. Here we analysed the responses to Al in two contrasting rice varieties. All analysed toxicity/tolerance markers (root elongation, Evans blue, morin and haematoxylin staining) indicated higher Al-tolerance in variety Nipponbare, than in variety Modan. Nipponbare accumulated much less Al in the roots than Modan. Aluminium supply caused stronger expression of STAR1 in Nipponbare than in Modan. A distinctively higher increase of Al-induced abscisic acid (ABA) accumulation was found in the roots of Nipponbare than in Modan. Highest ABA levels were observed in Nipponbare after 48 h exposure to Al. This ABA peak was coincident in time with the highest expression level of STAR1. It is proposed that ABA may be required for cell wall remodulation facilitated by the enhanced UDP-glucose transport to the walls through STAR1/STAR2. Contrastingly, in the roots of Modan the expression of both Nrat1 coding for a plasma membrane Al-transporter and of ALS1 coding for a tonoplast-localized Al transporter was considerably enhanced. Moreover, Modan had a higher Al-induced expression of ASR1 a gene that has been proposed to code for a reactive oxygen scavenging protein. In conclusion, the Al-exclusion strategy of Nipponbare, at least in part mediated by STAR1 and probably regulated by ABA, provided better protection against Al toxicity than the accumulation and internal detoxification strategy of Modan mediated by Nrat1, ALS1 and ARS1.
Plant Physiology Laboratory, Bioscience Faculty, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain.
Maite
M
Roselló
Plant Physiology Laboratory, Bioscience Faculty, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain. Electronic address: Charlotte.poschenrieder@uab.es.
Charlotte
C
Poschenrieder
Plant Physiology Laboratory, Bioscience Faculty, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain.
Benet
B
Gunsé
Plant Physiology Laboratory, Bioscience Faculty, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain.
Juan
J
Barceló
Plant Physiology Laboratory, Bioscience Faculty, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain.
Mercè
M
Llugany
D000535:Aluminum / Q000633:toxicity*; D004351:Drug Resistance / Q000235:genetics*; D018506:Gene Expression Regulation, Plant; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D008667:Metalloproteins / Q000235:genetics / Q000378:metabolism; D012275:Oryza / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D018517:Plant Roots / Q000187:drug effects / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
D026901:Membrane Transport Proteins; D008667:Metalloproteins; D010940:Plant Proteins; D014157:Transcription Factors; D000535:Aluminum
ALS1; Abscisic acid; Aluminium; Nrat1; Oryza sativa; STAR1