Project description:To better understand the mechanisms involved in aluminum (Al) toxicity and tolerance in plants, microarray technology was used to evaluate changes in gene expression in Arabidopsis thaliana under Al stress. With the use of Affymetrix Arabidopsis ATH1 Genechip, a comparison of RNA expression profiles was made between control and Al-treated Arabidopsis seedlings. A total of 256 genes were identified as Al-responsive. Ninety-four genes were shown to be up-regulated and 162 were down-regulated; comprising 1.1% of the 24,000 Arabidopsis genes. Real-time RT-PCR was used to confirm the microarray data. RNAs associated with known protein functions were classified into categories. The analysis showed that a large number of transcription factors and several putative signaling components were up-regulated by aluminum. Chloroplast structural and photosynthetic genes were, in general, down-regulated. A number of previously identified Al-responsive genes showed similar expression pattern changes in this study. For example, GST, Auxin-regulated, Peroxidase, and Chitinase, were found to be up-regulated by Al-stress, whereas, genes such as Wali 3 and Wali 4, were down-regulated. We also identified several up-regulated genes involved in vacuolar signaling, sorting and docking. Three genes were also up-regulated by Al-stress, Ras GTP-binding protein, ABC-cassette binding, and the AtELP1 receptor genes, have previously been documented as responsive to drought and/or oxidative stress and may play important roles the detoxification of Al ions by transportation and storage into root vacuoles. Ultrastructural changes in the roots tips cells of Arabidopsis were evaluated using TEM and EDXMA with SEM. Results using combined TEM and SEM-EDXMA showed that Al accumulattion in the root tip of Arabidopsis was detectable. The coupling these techniques can be useful for measuring Al in situ in cellular and sub cellular section of plant roots. SUBMITTER_CITATION: Goodwin, S., Sutter, TR.: (2008) Microarray Analysis of Arabidopsis Genome Response to Aluminum Stress. Biologia Plantarum 52 (2): 191 - 196. Experiment Overall Design: 2 biological replications for a total of 4 Affymetrix GeneChips, control and Al-treated, total RNA was extracted from 100 pooled Arabidopsis seedlings for each GeneChip.

Project description:Gene expression profiling in soybean under aluminum stress: Transcriptome response to Al stress in roots of Al-tolerant genotype (PI 416937). Aluminum (Al) toxicity is a major constraint of crop production on acid soils. Many commercial soybean cultivars and advanced breeding lines have been evaluated for Al tolerance. Aluminum tolerance is quantitatively inherited trait in soybean making it difficult for genetic improvement. Understanding the molecular and genetic mechanisms of tolerance is crucial for developing efficient and effective programs aimed at improving Al tolerance trait The molecular mechanisms of Al tolerance is poorly understood in soybean. The objective of the research was to identify candidate aluminum tolerance genes in soybean Al-tolerant soybean genotype PI 416937 seedlings were exposed to zero or 10 µM Al in growth chamber under hydroponic conditions for four time span of 2, 12, 48 and 72 hrs in a randomized complete block design with three replications. Microarray analysis was made on mRNA isolated from 1 cm log tap root tips using Affymetrix soybean array with over 68,000 probe sets Glycine max L and wild soybean combined. Both novel and known genes were discovered in response to Al treatment. They include Al tolerance relevant proteins, families of transcription factors, zinc finger, bZIP, WRKY, MYB, ADR6, and NAC domain proteins were induced likely regulating Al tolerance downstream genes. Stress related proteins, cytochrome P450, glutathione-s transferase, glutaredoxin family and ascorbic acid biosynthesis protein were induced as signatures of cellular detoxification mechanisms. An ABC type multidrug resistance protein that could act as citrate transporter or Al exporter was up-regulated, a key Al tolerance mechanisms in several species. A cell wall loosening enzyme endoxylglucan hydrolases were also up-regulated probably reversing the wall rigidification caused by Al and promoting root growth under Al stress. Phytosulfokines growth factor involved in cell division and proliferation was up-regulated likely as a direct counter action to Al toxicity which inhibits root growth by limiting cell division and elongation. In conclusion, the Al tolerance candidate genes identified herein are potential targets for future genetic engineering and molecular breeding work on Al tolerance trait in soybean which in turn would contribute to gain in soybean productivity on acid soils.

Project description:Background Ionic aluminum (mainly Al3+) is rhizotoxic and can be present in acid soils at concentrations high enough to inhibit root growth. Many forest tree species grow naturally in acid soils and often tolerate high concentrations of Al. Previously, we have shown that aspen (Populus tremula) releases citrate and oxalate from roots in response to Al exposure. To obtain further insights into the root responses of aspen to Al, we investigated root gene expression at Al conditions that inhibit root growth. Results Treatment of the aspen roots with 500 µM Al induced a strong inhibition of root growth within 6 h of exposure time. The root growth subsequently recovered, reaching growth rates comparable to that of control plants. Changes in gene expression were determined after 6 h, 2 d, and 10 d of Al exposure. Replicated transcriptome analyses using the Affymetrix poplar genome array revealed a total of 175 significantly up-regulated and 69 down-regulated genes, of which 70% could be annotated based on Arabidopsis genome resources. Between 6 h and 2 d, the number of responsive genes strongly decreased from 202 to 26, and then the number of changes remained low. The responses after 6 h were characterized by genes involved in cell wall modification, ion transport, and oxidative stress. Two genes with prolonged induction were closely related to the Arabidopsis Al tolerance genes ALS3 (for Al sensitive 3) and MATE (for multidrug and toxin efflux protein, mediating citrate efflux). Patterns of expression in different plant organs and in response to Al indicated that the two aspen genes are homologs of the Arabidopsis ALS3 and MATE. Conclusion Exposure of aspen roots to Al results in a rapid inhibition of root growth and a large change in root gene expression. The subsequent root growth recovery and the concomitant reduction in the number of responsive genes presumably reflect the success of the roots in activating Al tolerance mechanisms. The aspen genes ALS3 and MATE may be important components of these mechanisms.

Project description:Gene expression profiling in soybean under aluminum stress: Transcriptome response to Al stress in roots of Al-tolerant genotype (PI 416937). Aluminum (Al) toxicity is a major constraint of crop production on acid soils. Many commercial soybean cultivars and advanced breeding lines have been evaluated for Al tolerance. Aluminum tolerance is quantitatively inherited trait in soybean making it difficult for genetic improvement. Understanding the molecular and genetic mechanisms of tolerance is crucial for developing efficient and effective programs aimed at improving Al tolerance trait The molecular mechanisms of Al tolerance is poorly understood in soybean. The objective of the research was to identify candidate aluminum tolerance genes in soybean Al-tolerant soybean genotype PI 416937 seedlings were exposed to zero or 10 µM Al in growth chamber under hydroponic conditions for four time span of 2, 12, 48 and 72 hrs in a randomized complete block design with three replications. Microarray analysis was made on mRNA isolated from 1 cm log tap root tips using Affymetrix soybean array with over 68,000 probe sets Glycine max L and wild soybean combined. Both novel and known genes were discovered in response to Al treatment. They include Al tolerance relevant proteins, families of transcription factors, zinc finger, bZIP, WRKY, MYB, ADR6, and NAC domain proteins were induced likely regulating Al tolerance downstream genes. Stress related proteins, cytochrome P450, glutathione-s transferase, glutaredoxin family and ascorbic acid biosynthesis protein were induced as signatures of cellular detoxification mechanisms. An ABC type multidrug resistance protein that could act as citrate transporter or Al exporter was up-regulated, a key Al tolerance mechanisms in several species. A cell wall loosening enzyme endoxylglucan hydrolases were also up-regulated probably reversing the wall rigidification caused by Al and promoting root growth under Al stress. Phytosulfokines growth factor involved in cell division and proliferation was up-regulated likely as a direct counter action to Al toxicity which inhibits root growth by limiting cell division and elongation. In conclusion, the Al tolerance candidate genes identified herein are potential targets for future genetic engineering and molecular breeding work on Al tolerance trait in soybean which in turn would contribute to gain in soybean productivity on acid soils. One genotype PI 416937 (p); four time points: (2, 12, 48, and 72 hrs), with replicates (2 or 3)

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Microarray Analysis of Arabidopsis Genome Response to Aluminum Stress

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