Project description:Understanding the genetic basis of plants’ response to environmental stresses such as drought and salinity is vital for improving the future crop productivity and for deciphering the evolutionary mechanisms of adaptation and speciation. Here, we screened for genes and functional groups that are potentially involved in drought tolerance in tomato by comparing genome-wide transcriptome profiles of drought-sensitive S. lycopersicum and drought-tolerant S. pimpinellifolium populations under control and water deficit conditions. We also compared the transcriptome profiles from this study and a previous salt treatment study to investigate expression similarities and differences in gene expression patterns between water and salt stress responses, which are physiologically and biochemically similar. Stress-induced genes such as dehydration responsive element binding (DREB) protein, ABA-response element binding factor (AREB)-like protein, heat shock proteins, and chaperones were commonly up-regulated in S. lycopersicum and S. pimpinellifolium. Genes such as WRKY transcription factors and 1-aminocyclopropane-1-carboxylate (ACC) synthase exhibited striking differences in both the baseline expression under the control condition as well as expression changes in response to water deficit, suggesting that the two species have accumulated heritable differences in gene expression patterns. At the genome scale, there was a tendency that down-regulated genes in S. lycopersicum are more neutral or even up-regulated in S. pimpinellifolium, suggesting that S. pimpinellifolium may be able to maintain cellular activities during prolonged droughts. In comparison of water and salt stress responses, known stress-induced genes such as DREB protein, AREB-like protein, and nine-cis-epoxycarotenoid dioxygenase (NCED) were commonly up-regulated in response to these stresses. However, we also found fundamental differences between these stress responses in terms of genome-wide expression patterns, partly attributable to the difference in how these stresses were applied during the experiments.

Project description:Understanding the genetic basis of plants’ response to environmental stresses such as drought and salinity is vital for improving the future crop productivity and for deciphering the evolutionary mechanisms of adaptation and speciation. Here, we screened for genes and functional groups that are potentially involved in drought tolerance in tomato by comparing genome-wide transcriptome profiles of drought-sensitive S. lycopersicum and drought-tolerant S. pimpinellifolium populations under control and water deficit conditions. We also compared the transcriptome profiles from this study and a previous salt treatment study to investigate expression similarities and differences in gene expression patterns between water and salt stress responses, which are physiologically and biochemically similar. Stress-induced genes such as dehydration responsive element binding (DREB) protein, ABA-response element binding factor (AREB)-like protein, heat shock proteins, and chaperones were commonly up-regulated in S. lycopersicum and S. pimpinellifolium. Genes such as WRKY transcription factors and 1-aminocyclopropane-1-carboxylate (ACC) synthase exhibited striking differences in both the baseline expression under the control condition as well as expression changes in response to water deficit, suggesting that the two species have accumulated heritable differences in gene expression patterns. At the genome scale, there was a tendency that down-regulated genes in S. lycopersicum are more neutral or even up-regulated in S. pimpinellifolium, suggesting that S. pimpinellifolium may be able to maintain cellular activities during prolonged droughts. In comparison of water and salt stress responses, known stress-induced genes such as DREB protein, AREB-like protein, and nine-cis-epoxycarotenoid dioxygenase (NCED) were commonly up-regulated in response to these stresses. However, we also found fundamental differences between these stress responses in terms of genome-wide expression patterns, partly attributable to the difference in how these stresses were applied during the experiments. We compared Affymetrix microarray transcriptome profiles of root tissues from three natural populations each of S. lycopersicum and S. pimpinellifolium (3-4 individuals in each population as biological replicates under control (well-watered) and water deficit treatments.

Project description:Drought is an inevitable stress almost all terrestrial plants face in their life cycles. Desert dwelling plants show extreme adaptations to drought but their genomes are largely unexplored compared to drought sensitive model plants generally studied to understand plant drought tolerance. Haloxylon ammodendron is a pioneer species extremely tolerant to drought and capable of colonizing desert sand dunes. Seedling establishment is the most critical development stage in the survival of H. ammodendron. H. ammodendron seedlings are able to withstand high light, and low temperature stresses characteristic of temperate desert environments in addition to drought. We have investigated the genome-wide transcript responses under induced drought stress during early seedling establishment to identify prevailing basal and induced gene clusters that likely contribute to survival and stress adapted growth in H. ammodendron. We find staggering support for drought response transcript accumulation together with other transcripts that may transform the cellular expression space into a preadapted state for salt, light, osmotic, and temperature stress tolerance. While transcript accumulation is excessive for genes associated with abiotic stress tolerance under an induced drought treatment, H. ammodendron seems to enhance biotic stress tolerance simultaneously by down-regulation of several genes that would be found at an up-regulated state during pathogen entry in susceptible plants. We detected enriched basal level transcript allocation that suggests preadaptation to abiotic stresses as well as pathogen defense in H. ammodendron when compared to other Amaranthaceae family transcriptomes under stress neutral conditions. Amaranthaceae is one of the most enriched plant families for extremophytes. We found transcripts that are generally maintained at low levels and some induced only under abiotic stress in Arabidopsis thaliana to be highly expressed under basal conditions in the Amaranthaceae transcriptomes including H. ammodendron. These could be novel candidates to expand or initiate discovery of new stress adaptive gene networks and mechanisms naturally selected in extremophytes that allow survival under environmental stresses.

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Molecular responses of amaranth species to abiotic stresses

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