| Aluminum (Al) stress is a major limitation to crop productivity on acidic soils. To help understand the cellular mechanisms underlying the toxicity and resistance of plants to Al, this thesis involved a large-scale, transcriptomic and proteomic analysis of roots of Arabidopsis thaliana and reports on comparative analysis of transcriptome and proteome of Al stress responses. Using a microarray representing ∼93% of the predicted genes in Arabidopsis, a relatively small proportion (3%) of transcripts were detected as Al-responsive. More changes in the transcriptome were detected after long-term (48 h; 1,114 genes), than short-term (6 h; 401 genes) with relatively little overlap of transcripts detected for each time point. These results suggest that Al toxicity is progressive over time and poses some unique challenges to plants. Further, using two dimensional differential in gel electrophoresis (DiGE), 12 (6 h) and 17 (48 h) proteins were found differentially abundant after Al exposure. Most of the identified proteins were involved in primary metabolism and oxidative stress. Cytosolic-malate dehydrogenase (cyt-MDH) was one of the novel Al-responsive protein identified in this study. Transcript abundance of cyt-MDH correlated well with protein abundance, suggesting that cyt-MDH is regulated in part at transcriptional level. Furthermore, homozygous mdh-1 and mdh-2 mutants were more resistant to Al as compared to WT suggesting that regulation of cyt-MDH could play a role in Al resistance. In general, comparative analysis of proteomics data and transcriptomics data showed a poor correlation for both 6 h (r2 = 0.155) and 48 h (r2 = 0.083).;The potential role of five class III peroxidases (PER2, PER27, PER34, PER42, PER69) in resistance of roots to Al was explored using quantitative reverse transcriptase PCR and a reverse genetics approach. A diverse range of patterns of transcript abundance was detected using QRT-PCR in response to Al. Furthermore, per2, per21, and per69 mutants showed greater increases in root lengths as compared to WT after Al stress suggesting that regulation of PER might play a role in Al resistance. These results contribute to the identification of candidate genes for the generation of Al-resistant transgenic plants. |
