Transcriptomic responses to aluminum stress in roots of Arabidopsis thaliana.

To help characterize the cellular mechanisms underlying the toxicity of Al to plants, we present the first large-scale, transcriptomic analysis of root responses to Al, using a microarray representing approximately 93% of the predicted genes in the genome of Arabidopsis. More transcripts were responsive to Al (25 microM) during long (48 h, 1,114 genes), as compared to short (6 h, 401 genes) exposures, which contrasts with previous microarray analyses of plant responses to other types of abiotic stress. Exposure to Al triggered changes in the transcript levels for several genes related to oxidative stress pathway, membrane transporters, cell wall, energy, and polysaccharide metabolism. Interestingly, lack of abundance of transcripts encoding TCA cycle enzymes, except for malate dehydrogenase, suggested that synthesis of organic anions in response to Al may not be transcriptionally regulated. Al exposures induced differential abundance of transcripts for several ribosomal proteins, peptidases and protein phosphatases mostly after 48 h. We also detected increased abundance of transcripts for several membrane receptor kinases and non-membrane calcium response kinases, which could play a role in transmission of Al-stress signals. Among Al responsive transcription factors, the most predominant families identified were AP2/EREBP, MYB and bHLH. Further, we studied the kinetics of Al stress responses for class III peroxidases using Q-RT-PCR. Our results indicated that Al triggered dynamic changes in transcript abundance of various peroxidases within 1 h. The results of this screen contribute to the identification of candidate genes for the generation of Al-tolerant transgenic plants.