Oligonucleotide microarrays corresponding to over 16,000 genes were used to analyze changes in transcript accumulation in root tips of the Al-sensitive Medicago truncatula cultivar Jemalong genotype A17 in response to Al treatment. Out of 2,782 genes with significant changes in transcript accumulation, 324 genes were up-regulated and 267 genes were down-regulated at least twofold by Al. Up-regulated genes were enriched in transcripts involved in cell-wall modification and abiotic and biotic stress responses while down-regulated genes were enriched in transcripts involved in primary metabolism, secondary metabolism, protein synthesis and processing, and the cell cycle. Known markers of Al-induced gene expression including genes associated with oxidative stress and cell wall stiffening were differentially regulated in this study. Transcript profiling identified novel genes associated with processes involved in Al toxicity including cell wall modification, cell cycle arrest and ethylene production. Novel genes potentially associated with Al resistance and tolerance in M. truncatula including organic acid transporters, cell wall loosening enzymes, Ca2+ homeostasis maintaining genes, and Al-binding were also identified. In addition, expression analysis of nine genes in the mature regions of the root revealed that Al-induced gene expression in these regions may play a role in Al tolerance. Finally, interfering RNA-induced silencing of two Al-induced genes, pectin acetylesterase and annexin, in A17 hairy roots slightly increased the sensitivity of A17 to Al suggesting that these genes may play a role in Al resistance.
Bibliographical noteFunding Information:
Acknowledgments This work was supported by the National Science Foundation Plant Genome Project (award no. 0110206) and USDA-ARS. We thank Dr. Susan C. Miyasaka (University of Hawaii) for providing us with the media composition for Al-plate assays, Dr. David Galbraith (University of Arizona) for printing of microarrays, Dr. Dasharath P. Lohar (University of Minnesota) for microarray slide scanning and Dr. Judy Schnurr for assistance with RNA blots. We acknowledge support from the University of Minnesota Super Computing Institute for data analysis. This paper is a joint contribution from the Plant Science Research Unit, USDA, Agricultural Research
Copyright 2009 Elsevier B.V., All rights reserved.
- Aluminum toxicity
- Barrel medic
- Organic acid
- RNA interference