Search Results (9)

To unravel the mechanisms underpinning salt tolerance, different studies have attempted to determine the physiological and genetic variations behind the difference in salt tolerance between Arabidopsis thaliana and the salt-tolerant Thellungiella salsuginea (halophila). Most of these studies were limited to a specific duration of salt treatment and neglected the time response as a possible contributing factor to the higher salt tolerance exhibited by T. salsuginea. In this work, a comprehensive and detailed comparison of the response of the two species to high salinity was conducted at different times for up to ten days of salt treatment. T. salsuginea responded more rapidly and to a higher extent to adjust its metabolism and showed constitutive levels of anticipatory metabolism to salinity. T. salsuginea responded more rapidly in terms of maintaining light use efficiency, limiting the uptake of Na⁺, and increasing the accumulation of sugars and proline when exposed to salinity. T. salsuginea had much higher constitutive levels of metabolites, including malate, proline, and inositol, in comparison to A. thaliana. Interestingly, T. salsuginea showed a reduction in malate levels under salt treatment in contrast to A. thaliana. These results suggest that constitutive levels and the rapidity of the deployment of resistance mechanisms, together with metabolic plasticity, in response to salt stress are important adaptive traits for salt tolerance in plants. Full article

Salt cress (Eutrema salsugineum, aka Thellungiella salsuginea) is an extremophile and a close relative of Arabidopsis thaliana. To understand the mechanism of selection of complex traits under natural variation, we analyzed the physiological and proteomic differences between Shandong (SD) and Xinjiang (XJ) ecotypes. The SD ecotype has dark green leaves, short and flat leaves, and more conspicuous taproots, and the XJ ecotype had greater biomass and showed clear signs of senescence or leaf shedding with age. After 2-DE separation and ESI-MS/MS identification, between 25 and 28 differentially expressed protein spots were identified in shoots and roots, respectively. The proteins identified in shoots are mainly involved in cellular metabolic processes, stress responses, responses to abiotic stimuli, and aging responses, while those identified in roots are mainly involved in small-molecule metabolic processes, oxidation-reduction processes, and responses to abiotic stimuli. Our data revealed the evolutionary differences at the protein level between these two ecotypes. Namely, in the evolution of salt tolerance, the SD ecotype highly expressed some stress-related proteins to structurally adapt to the high salt environment in the Yellow River Delta, whereas the XJ ecotype utilizes the specialized energy metabolism to support this evolution of the short-lived xerophytes in the Xinjiang region. Full article

The increased demand in vegetable oil for food purposes and high-protein feed for livestock and poultry encourages producers to expand the production of various oil crops, while occupying rather cold agroclimatic zones. Improved cold and frost resistance of cultivated crops would significantly increase the yield and expand the range of rape cultivation in a number of cold climate regions. Nine transgenic lines of winter rape containing genes encoding proteins with a cold shock domain (CspA и EsCSDP3) were obtained as a result of Agrobacterium transformation. In total, 260 explants were involved in transformation of rape using pBI121-CSPA-plant, with a transformation efficiency of 2.3%; among 750 explants using the pBI-EsCSDP3 construction, the efficiency was 0.4%. As a result of the studies, it was shown that the expression of the new gene Escsdp3 from the plant of Eutrema salsugineum was able to increase the cold and frost resistance of plants as effectively as the cspa gene from E. coli, which is classically used for this purpose. The cold resistance analysis of T₁ transgenic plants generation revealed four cold resistant winter rape lines (three lines with the cspA-plant gene and one line with the Escsdp3 gene). The transfer of Escsdp3 and cspA-plant genes into winter rape plants led to a significant increase in frost resistance of plants. Two winter rapeseed lines were resistant to freezing (with the cspA-plant gene and with the Escsdp3 gene). Non-hardened transgenic plants remained viable after 24 h of exposure to negative temperatures up to −5 °C, and plants that passed through the hardening stage survived after freezing at −16 °C. Full article

Low-oxygen stress, mainly caused by soil flooding, is a serious abiotic stress affecting crop productivity worldwide. To understand the mechanisms of low-oxygen stress responses and adaptation of plants, we characterized and compared low-oxygen responses in six species with different accessions of the Brassicaceae family. Based on the growth and survival responses to submergence or low-oxygen condition, these accessions could be divided into three groups: (i) Highly tolerant species (Rorippa islandica and Arabis stelleri); (ii) moderately tolerant species (Arabidopsis thaliana [esk-1, Ler, Ws and Col-0 ecotype]); and (iii) intolerant species (Thlaspi arvense, Thellungiella salsuginea [Shandong and Yukon ecotype], and Thellungiella parvula). Gene expression profiling using Operon Arabidopsis microarray was carried out with RNA from roots of A. thaliana (Col-0), A. stelleri, R. islandica, and T. salsuginea (Shandong) treated with low-oxygen stress (0.1% O₂/99.9% N₂) for 0, 1, 3, 8, 24, and 72 h. We performed a comparative analysis of the gene expression profiles using the gene set enrichment analysis (GSEA) method. Our comparative analysis suggested that under low-oxygen stress each species distinctively reconfigures the energy metabolic pathways including sucrose–starch metabolism, glycolysis, fermentation and nitrogen metabolism, tricarboxylic acid flow, and fatty acid degradation via beta oxidation and glyoxylate cycle. In A. thaliana, a moderately tolerant species, the dynamical reconfiguration of energy metabolisms occurred in the early time points of low-oxygen treatment, but the energy reconfiguration in the late time points was not as dynamic as in the early time points. Highly tolerant A. stelleri appeared to have high photosynthesis capacity that could produce more O₂ and in turn additional ATP energy to cope with energy depletion caused by low-oxygen stress. R. islandica seemed to retain some ATP energy produced by anaerobic energy metabolism during a prolonged period of low-oxygen conditions. Intolerant T. salsuginea did not show significant changes in the expression of genes involved in anaerobic energy metabolisms. These results indicate that plants developed different energy metabolisms to cope with the energy crisis caused by low-oxygen stress. Full article

Plant cuticle lipids form outer protective layers to resist environmental stresses; however, the relationship between cuticle properties and cold tolerance is unclear. Here, the extremophyte Thellungiella salsuginea was stressed under cold conditions (4 °C) and the cuticle of rosette leaves was examined in terms of epicuticular wax crystal morphology, chemical composition, and cuticle-associated gene expression. The results show that cold induced formation of distinct lamellas within the cuticle ultrastructure. Cold stress caused 14.58% and 12.04% increases in the amount of total waxes and cutin monomer per unit of leaf area, respectively, probably associated with the increase in total fatty acids. The transcriptomic analysis was performed on rosette leaves of Thellungiella exposed to cold for 24 h. We analyzed the expression of 72 genes putatively involved in cuticle lipid metabolism, some of which were validated by qRT-PCR (quantitative reverse transcription PCR) after both 24 h and one week of cold exposure. Most cuticle-associated genes exhibited higher expression levels under cold conditions, and some key genes increased more dramatically over the one week than after just 24 h, which could be associated with increased amounts of some cuticle components. These results demonstrate that the cuticle provides some aspects of cold adaptation in T. salsuginea. Full article

Plant responses to abiotic stresses entail adaptive processes that integrate both physiological and developmental cues. However, the adaptive traits that are involved in the responses to a high soil salinity during reproductive growth are still poorly studied. To identify new clues, we studied the halophyte, Thellungiella salsuginea, and three Arabidopsis accessions, known as tolerant or salt-sensitive. We focused on the quantitative traits associated with the stem growth, sugar content, and anatomy of the plants subjected to the salt treatment, with and without a three-day acclimation, applied during the reproductive stage. The stem growth of Thellungiella salsuginea was not affected by the salt stress. By contrast, salt affected all of the Arabidopsis accessions, with a natural variation in the effect of the salt on growth, sugar content, and stem anatomy. In response to the high salinity, irregular xylem vessels were observed, independently of the accession’s tolerance to salt treatment, while the diameter of the largest xylem vessels was reduced in the tolerant accessions. The stem height, growth rate, hexoses-to-sucrose ratio, and phloem-to-xylem ratio also varied, in association with both the genotype and its tolerance to salt stress. Our findings indicate that several quantitative traits for salt tolerance are associated with the control of inflorescence growth and the adjustment of the phloem-to-xylem ratio. Full article

Aquaporins play important regulatory roles in the transport of water and small molecules in plants. In this study, a Thellungiella salsuginea TsPIP1;1 aquaporin was transformed into Kitaake rice, and three transgenic lines were evaluated by profiling the changes of the physiological metabolism, osmotic potential, and differentially expressed genes under salt stress. The TsPIP1;1 protein contains six transmembrane domains and is localized in the cytoplasm membrane. Overexpression of the TsPIP1;1 gene not only increased the accumulation of prolines, soluble sugars and chlorophyll, but also lowered the osmotic potential and malondialdehyde content in rice under salt stress, and alleviated the amount of salt damage done to rice organs by regulating the distribution of Na/K ions, thereby promoting photosynthetic rates. Transcriptome sequencing confirmed that the differentially expressed genes that are up-regulated in rice positively respond to salt stimulus, the photosynthetic metabolic process, and the accumulation profiles of small molecules and Na/K ions. The co-expressed Rubisco and LHCA4 genes in rice were remarkably up-regulated under salt stress. This data suggests that overexpression of the TsPIP1;1 gene is involved in the regulation of water transport, the accumulation of Na/K ions, and the translocation of photosynthetic metabolites, thus conferring enhanced salt tolerance to rice. Full article

Photosynthetic organisms are able to sense energy imbalances brought about by the overexcitation of photosystem II (PSII) through the redox state of the photosynthetic electron transport chain, estimated as the chlorophyll fluorescence parameter 1-q_L, also known as PSII excitation pressure. Plants employ a wide array of photoprotective processes that modulate photosynthesis to correct these energy imbalances. Low temperature and light are well established in their ability to modulate PSII excitation pressure. The acquisition of freezing tolerance requires growth and development a low temperature (cold acclimation) which predisposes the plant to photoinhibition. Thus, photosynthetic acclimation is essential for proper energy balancing during the cold acclimation process. Eutrema salsugineum (Thellungiella salsuginea) is an extremophile, a close relative of Arabidopsis thaliana, but possessing much higher constitutive levels of tolerance to abiotic stress. This comparative study aimed to characterize the photosynthetic properties of Arabidopsis (Columbia accession) and two accessions of Eutrema (Yukon and Shandong) isolated from contrasting geographical locations at cold acclimating and non-acclimating conditions. In addition, three different growth regimes were utilized that varied in temperature, photoperiod and irradiance which resulted in different levels of PSII excitation pressure. This study has shown that these accessions interact differentially to instantaneous (measuring) and long-term (acclimation) changes in PSII excitation pressure with regard to their photosynthetic behaviour. Eutrema accessions contained a higher amount of photosynthetic pigments, showed higher oxidation of P700 and possessed more resilient photoprotective mechanisms than that of Arabidopsis, perhaps through the prevention of PSI acceptor-limitation. Upon comparison of the two Eutrema accessions, Shandong demonstrated the greatest PSII operating efficiency (Φ_PSII) and P700 oxidizing capacity, while Yukon showed greater growth plasticity to irradiance. Both of these Eutrema accessions are able to photosynthetically acclimate but do so by different mechanisms. The Shandong accessions demonstrate a stable response, favouring energy partitioning to photochemistry while the Yukon accession shows a more rapid response with partitioning to other (non-photochemical) strategies. Full article

Glutathione peroxidases (GPX) catalyze the reduction of H₂O₂ or organic hydroperoxides to water or corresponding alcohols using reduced glutathione, which plays an essential role in ROS (reactive oxygen species) homeostasis and stress signaling. Thellungiella salsuginea (Eutrema salsugineum), a relative of Arabidopsis thaliana, displays an extremely high level of tolerance to salt, drought, cold and oxidative stresses. The enzymatic antioxidant systems may contribute to the stress tolerance of T. salsuginea. In the present study, we aimed at understanding the roles of the antioxidant enzymes in T. salsuginea by focusing on the GPX family. We identified the eight GPX genes in T. salsuginea, and the structure of the N-terminal domains indicated their putative chloroplastic, mitochondrial and cytoplasmic location. The exon-intron organization of these genes exhibited a conserved pattern among plant GPX genes. Multiple environmental stresses and hormone response related cis-acting elements were predicted in the promoters of TsGPX genes. The gene and protein expression profiles of TsGPXs in response to high level of salinity and osmotic stresses, in leaves and roots of T. salsuginea were investigated using real-time RT-PCR and western blotting analysis. Our result showed that different members of the GPX gene family were coordinately regulated under specific environmental stress conditions, and supported the important roles of TsGPXs in salt and drought stress response in T. salsuginea. Full article