Project description:The overall objective was to document transcriptomic changes in the guard cells of Arabidopsis thaliana under short (1x) - and long-term (3x) saline growth conditions. Guard cells of Arabidopsis responded also to the intensity of the salt management by the microarray datasets clearly clustering in (-) salt, 1x salt and 3x salt. Similarly, more GO terms were significantly enriched in differentially expressed guard cell genes of 1 x salt than 3x salt treated plants.
Project description:Mannitol is a putative osmoprotectant contributing to salt tolerance in several species. Arabidopsis plants transformed with the mannose-6-phosphate reductase (M6PR) gene from celery were dramatically more salt tolerant (at 100 mM NaCl) as exhibited by reduced salt injury, less inhibition of vegetative growth, and increased seed production relative to the wild type (WT). When treated with 200 mM NaCl, transformants produced no seeds, but did bolt, and exhibited less chlorosis/necrosis and greater survival and dry weights than the WT. Without salt there were no M6PR effects on growth or phenotype, but expression levels of 2272 genes were altered. Many fewer differences (1039) were observed between M6PR and WT plants in the presence of salt, suggesting that M6PR pre-conditioned the plants to stress. Previous work suggested that mannitol is an osmoprotectant, but mannitol levels are invariably quite low, perhaps inadequate for osmoprotectant effects. In this study, transcriptome analysis reveals that the M6PR transgene activated the downstream abscisic acid (ABA) pathway by up-regulation of ABA receptor genes (PYL4, PYL5, and PYL6) and down-regulation of protein phosphatase 2C genes (ABI1 and ABI2). In the M6PR transgenic lines there were also increases in transcripts related to redox and cell wall-strengthening pathways. These data indicate that mannitol-enhanced stress tolerance is due at least in part to increased expression of a variety of stress-inducible genes.
Project description:Arabidopsis thaliana is a glycophyte with a low salt tolerance, while Eutrema is a halophyte with a very high salt tolerance. To elucidate the transcriptional basis of this difference, we performed hydroponis culture experiments where we grew plants under control conditions (25 mM NaCl) or under salt stress (200 mM NaCl for both species, 500 mM for Eutrema). Salt concentration was increased for the stress treatments by increments of 50 mM per day (25 mM on the first day). Plants were grown at the final NaCl concentration for an additional week, when rosettes were harvested for RNA isolation.Expression patterns were compared between treatments and between species.
Project description:Mannitol is a sugar alcohol that serves as a compatible solute contributing to exceptional salt tolerance in several plant species. Arabidopsis plants transformed with the mannose-6-phosphate reductase (M6PR) gene from celery were dramatically more salt tolerant. Following treatment with 100mM NaCl, transgenic plants, relative to wild type (WT), were more successful in bolting, flowering, and production of viable seed, were less chlorotic/necrotic, and with less inhibition of growth (leaf number, rosette diameter, plant height, stalk number, and dry weight). When irrigated with 200 mM NaCl, both transformants and WT plants died without producing seeds, but M6PR transformants bolted and showed significantly less chlorosis and necrosis and had higher survival rates and dry weights than those of WT. Under normal growth conditions there were no negative effects of the M6PR transgene on overall growth (leaf number, rosette diameter, plant height, stalk number, and dry weight), or time to bolting/flowering or seed production compared to wild type (WT). Despite the lack of effects on phenotype in the absence of salt stress, genome wide expression analyses indicated that expression levels of more than 2000 genes were altered by presence of the M6PR transgene: however, there were many fewer differences observed between the M6PR and non-transgenic plants in the presence of salt stress (459), suggesting that M6PR pre-conditioned the plants for exposure to salinity. Gene categories most affected in the M6PR transgenic plants were involved in DNA binding, signal transduction, metabolism/energy, cell structure, membrane transport, defense response, and transcription. Notably, a large number of known stress genes were induced, including those related to cell walls, biotic stress, and ABA- and ethylene-responses. Our work and that in other labs has suggested that mannitol acts as an osmoprotectant, but mannitol levels are invariably quite low, and perhaps inadequate to explain its effects as an osmoprotectant. The gene expression data here indicate that stress tolerance of mannitol-producing Arabidopsis is also due, at least in part, to enhanced expression of a number of stress inducible genes related to both biotic and abiotic stress tolerance. Both M6PR transgenic and Col WT plants were grown in the growth chamber in the absence and presence of salt stress. Plants from 20 days after sowing (6 days after salt treatment) were used for RNA extraction and hybridization on Affymetrix microarrays. There were two biological replicates for each genotype and salt treatment combination.
Project description:Gene expression was compared between non-stress Arabidopsis plants (0 hr salt treatment) and salt treated plants (2 hrs and 10 hrs salt treatment).
Project description:Salt stress is one of the most severe environmental conditions which cause huge losses in crop production worldwide. We identified an essential regulator of salt stress RSA3 and used the Affymetrix whole-genome arrays to study the effect of rsa3-1 mutation on global gene expression under salt stress. A set of genes differentially expressed in rsa3-1 under salt stress are identified.