Overexpression of GhGSTF9 Enhances Salt Stress Tolerance in Transgenic Arabidopsis.

Soil salinization is a major abiotic stress factor that negatively impacts plant growth, development, and crop yield, severely limiting agricultural production and economic development. Cotton, a key cash crop, is commonly cultivated as a pioneer crop in regions with saline-alkali soil due to its relatively strong tolerance to salt. This characteristic renders it a valuable subject for investigating the molecular mechanisms underlying plant salt tolerance and for identifying genes that confer salt tolerance. In this study, focus was placed on examining a salt-tolerant variety, E991, and a salt-sensitive variety, ZM24. A combined analysis of transcriptomic data from these cotton varieties led to the identification of potential salt stress-responsive genes within the glutathione S-transferase (GST) family. These versatile enzyme proteins, prevalent in animals, plants, and microorganisms, were demonstrated to be involved in various abiotic stress responses. Our findings indicate that suppressing GhGSTF9 in cotton led to a notably salt-sensitive phenotype, whereas heterologous overexpression in Arabidopsis plants decreases the accumulation of reactive oxygen species under salt stress, thereby enhancing salt stress tolerance. This suggests that GhGSTF9 serves as a positive regulator in cotton's response to salt stress. These results offer new target genes for developing salt-tolerant cotton varieties.

Comparative assessment of metabolic, ionic and molecular responsiveness of four facultative halophytes to habitat salinization in the southwest of Jeddah Governorate, Saudi Arabia.

This study explores the influence of salinity on some physiological and biochemical pathways of four facultative halophytes (Abutilon pannosum, Indigofera oblongifolia, Senna italica, and Tetraena coccinea) along the southwest coast of Jeddah Governorate. Through a comparative analysis of these plants in both saline and non-saline environments, the study investigates chlorophyll levels, ion concentrations within the plants, the correlation with the SOS1 gene, and the impact of salinity on metabolic compounds. The overarching goal is to gain insights into the adaptive mechanisms of these specific plants to salt stress, providing valuable information for addressing global agricultural challenges associated with salinity. Throughout the study, metabolic, ionic, and molecular responses of these plants were scrutinized in both environments. The findings revealed elevated levels of Na+, K+, Ca2+, and Mg2+ in saline habitats, except for Na+ in I. oblongifolia. Despite increased concentrations of Chl b, variations were noted in Chl a and carotenoids in plants exposed to salt. Osmoregulatory patterns in A. pannosum and I. oblongifolia exhibited reversible changes, including heightened protein and proline levels in A. pannosum and decreased levels in I. oblongifolia, accompanied by alterations in amino acids and soluble carbohydrates. Senna italica displayed higher levels of osmolytes, excluding proline, compared to salinized environments, while T. coccinea exhibited lower levels of amino acids. The accumulation of Na+ emerged as the primary mechanism for ionic homeostasis in these plants, with non-significant decreases observed in K+, Mg2+, and Ca2+. Notably, an overexpression of the SOS1 gene (plasma membrane Na+/H+ antiporter) was observed as a response to maintaining ionic balance. Understanding these halophytes will be critical in addressing salinity challenges and enhancing crop tolerance to salinity.

Assessment of halophyte plant phenotypic responses under heavy metals pollution. Implications for monitoring and phytoremediation.

While phytoremediation is a highly valued practice to address local pollution problems, the use of early biomarkers of stress is useful for monitoring environments since they allow us to take measures before deleterious effects are irreversible. In this framework the goals are: to evaluate the pattern of leaf shape variation of Limonium brasiliense plants related to a metal soil gradient in the San Antonio salt marsh; to assess whether seeds from sites with different pollution levels show the same pattern of leaf shape variations under optimal growing conditions; and to compare the growth, the Pb accumulation pattern, and the leaf shape variation pattern of plants germinated from seeds originated in sites with different pollution levels in response to an experimental Pb rise. The results obtained from leaves collected in the field showed that the leaf shape changed depending on the soil metal levels. Plants germinated from seeds collected at the different sites expressed all the variation in leaf shape independently of the origin site, and the mean shape of each site was close to the consensus. Instead, when looking for the leaf shape components that maximize the differences between the sites from a growth experiment exposed to an increase in Pb in the irrigation solution, the pattern of variation found in the field disappeared. That is, only plants from the polluted site did not show variations in leaf shape in response to Pb additions. Finally, Pb accumulation in the roots was highest in plants germinated from seeds from the site where the soil pollution is greater. That suggests that seeds of L. brasiliense from polluted sites are better to use in phytoremediation practices, specifically to stabilize Pb in its roots whilst plants from the non-polluted site are better to detect pollutant soils using the leaf shape as an early biomarker.

Assessment of cadmium and lead tolerance potential of quinoa (Chenopodium quinoa Willd) and its implications for phytoremediation and human health.

Soil contamination with Cd and Pb is a worldwide problem which not only degrades the environment but also poses a serious threat for human and animal health. Phytoremediation of these contaminated soils using halophytic plants like quinoa presents an opportunity to clean the soils and use them for crop production. The current experiment was performed to evaluate the Cd and Pb tolerance potential of quinoa and subsequently its implications for human health. Three weeks old quinoa seedlings were exposed to Cd (30, 60 and 90 mg kg-1) and Pb (50, 100 and 150 mg kg-1) levels along with a control. The results revealed that plant height decreased at highest levels of soil Cd and Pb. Shoot, root and seed dry weight decreased with increasing levels of soil Cd and Pb. Tissue Cd and Pb concentrations increased with increasing levels of Cd and Pb in soil, the highest Cd was found in roots while the lowest in seeds. The highest Pb concentration was found in shoots at low Pb level, while in roots at high level of Pb. Increasing levels of Cd and Pb stimulated the activities of measured antioxidant enzymes and decreased membrane stability index. The health risk assessments of Cd and Pb revealed that hazard quotient was < 1 for both the metals. However, the results of total hazard quotient showed that value was < 1 for Pb and 1.19 for Cd showing potential carcinogenicity. This study demonstrates that quinoa has good phytoremediation potential for Cd and Pb however, the risk of Cd toxicity is challenging for human health.

Comparative assessment of heavy metal accumulation and bio-indication in coastal dune halophytes.

This study aimed at assessing heavy metals (Fe, Mn, Zn, Cu, Cr and Pb) in four perennial halophytes (viz. Heliotropium bacciferum, Halopyrum mucronatum, Ipomoea pes-caprae and Salsola imbricata) growing at two sites on the Karachi coast. Site - II, closer to the Industrial area had higher bioavailability as well as translocation factor (TF) for most of the heavy metals and Na+ where soil sediments had lower pH (approximately 7.5), higher salinity (EC) and organic matter (OM). Site - I which was far from Industrial area had comparatively higher bio-concentration factor (BCF) and lower TF for metal ions and soil pH of 8.1-9. Metal accumulation in plants was both site and species specific. Extractable concentration of shoot Pb in all tested halophytes was above normal of the threshold values (i.e., >0.3 mg kg-1) while Mn (<50 mg kg-1) and Cu (<40 mg kg-1) were within permissible limits. Salsola imbricata had highest Na+ at both sites (site - I = 73; site - II = 98 mg kg-1) with and 10 mg kg-1 extractable shoot Pb at site - I. Ipomea pes-caprae also accumulated shoot Pb higher than normal (site - I = 3.3; site - II = 0.8 mg kg-1) with lowest Na+ content. Heliotropium bacciferum had higher extractable Pb (site - I = 10.5; II = 2.75) with >20 mg kg-1 Na+ in shoot while maintaining > 1 TF for Pb, Cu, Mn and Zn at site - I and all tested metals at site - II. Halopyrum mucronatum had highest shoot Fe (644 mg kg-1), Zn (63 mg kg-1) and Cr (9.2 mg kg-1) at site - II and above threshold values of Pb at both sites (site - I = 8.2; site - II = 2.5 mg kg-1) which makes this species an ideal bio-indicator candidate while other species could be potentially used for Pb phytoremediation.

Assessment of phytoremediation capacity of three halophytes: Suaeda monoica, Tamarix indica and Cressa critica.

Halophyte is a distinctive group of plants that can survive, even well flourish, at a concentration of Na+ and Cl- ions along with heavy metals that would be lethal to most of the agricultural crop species. These capabilities make certain halophytes good contenders for phytoremediation through phytoextraction or phytostabilization of the salt and heavy metals (HMs) in polluted soils. Thus, the present study elucidates the phytoextraction capacity of three halophytes (Suaeda monoica, Tamarix indica and Cressa critica) growing in saline soil (EC 112 ds m-1), with higher level of HMs rather than a cultivated soil. The accumulation of ions in above-ground tissue was determined in the all three studied plants, considering the fact that maintaining a stable cytosolic Na+/K+ ratio has become a crucial salinity tolerance mechanism. The higher salinity of soil resulted in high level of Na+ ions in leaves, increased synthesis of osmolyte components and robust antioxidant activities to combat the oxidative stress. As whole, changes in cellular metabolites were determined by using FT-IR spectroscopy, evident as differential FT-IR profiles in both leaves and stem specific to these metabolites. The considerable amounts of HMs accumulation including Zn, Fe, Mn, Cu, Cr, and Cd with highest being Fe in above-ground tissue of all three studied halophytes were obtained. These preliminary findings represent S. monoica, T. indica and C. cretica as potent phytoremediation plant using phytosequestration to accumulate HMs. The present study project a light on the use of these three plants in reclamation of degraded saline soils.

The energy cost of the tonoplast futile sodium leak.

Active removal of Na+ from the cytosol into the vacuole plays a critical role in salinity tissue tolerance, but another, often neglected component of this trait is Na+ retention in vacuoles. This retention is based on an efficient control of Na+ -permeable slow- and fast-vacuolar channels that mediate the back-leak of Na+ into cytosol and, if not regulated tightly, could result in a futile cycle. This Tansley insight summarizes our current knowledge of regulation of tonoplast Na+ -permeable channels and discusses the energy cost of vacuolar Na+ sequestration, under different scenarios. We also report on a phylogenetic and bioinformatic analysis of the plant two-pore channel family and the difference in its structure and regulation between halophytes and glycophytes, in the context of salinity tolerance.

Decision tree for mapping of halophyte cover around Ghannouch, Tunisia.

Environment of Ghannouch in the south-east of Tunisia is characterized by the wide-spread hypersaline soils, typically colonized by halophytes. The study of their distribution is required in order to reveal the extent of salinization and its dynamic. Mapping and monitoring with a remote sensing approach are foreseen as the ways to trace the spatial and temporal dimensions of the phenomenon. The identification of halophyte vegetation can take advantage by analyzing optical remote sensing data. Here, we propose using a decision tree approach applied to European Space Agency Sentinel-2 imagery, for an accurate land cover mapping of Ghannouch district in Gabès governorate. Data pre-processing was carried out using the European Space Agency's Sentinel Application Platform and the SEN2COR toolboxes. The mapping approach combines the spectral information in several channels of the visible-near-infrared spectrum. The land cover identification was performed following a spectral classification approach, exploiting several optical indices, normalized difference water index, normalized difference vegetation index, and several soil salinity index, in order to elaborate a decision tree algorithm. As a result, for an area of interest of 50 × 50 km2, at least 68% was classified as halophyte land cover. This mapping exercise represents an important step toward improved halophytes mapping in Tunisia and could be used to monitor the status of other salinity prone regions in the world.

Desalination of sea water with aquatic lily (Eichhornia crassipes).

During the last decades, methods of halo conditioning have been developed to increase the tolerance to salinity in glucophyta crops. Some experiments have carried out the application of hydrogen peroxide (H2O2), in support to the modification of cell tolerance in saline medium. The first objective of this study was to evaluate the effects of the incorporation of H2O2 in salinity tolerance development of the aquatic lily (Eichhornia crassipes). Results showed that the incorporation of 0.03 % H2O2 salinity tolerance developed in salt concentrations similar to seawater. Saline stress tolerance in aquatic lily was shown by the excretion of salts in its leaves; this process helped also in removing salt from seawater. At the same time, the reproduction of the lily is intimately linked to the content of nitrogen (N) and phosphorus (P) (nutrients) in water. This reason is important to control the concentrations of these elements in the water. This will allow maintaining a control in the dissemination of the lily. Considering the mentioned above, the second objective was to continue development of the adaptation of the aquatic lily in seawater, using H2O2 and the required amount of nutrients. This paper points out the importance of considering a biological process for the treatments in the desalination of seawater, making the process more sustainable.

Salinity tolerance of crops - what is the cost?

Soil salinity reduces crop yield. The extent and severity of salt-affected agricultural land is predicted to worsen as a result of inadequate drainage of irrigated land, rising water tables and global warming. The growth and yield of most plant species are adversely affected by soil salinity, but varied adaptations can allow some crop cultivars to continue to grow and produce a harvestable yield under moderate soil salinity. Significant costs are associated with saline soils: the economic costs to the farming community and the energy costs of plant adaptations. We briefly consider mechanisms of adaptation and highlight recent research examples through a lens of their applicability to improving the energy efficiency of crops under saline field conditions.

'Halophyte filters': the potential of constructed wetlands for application in saline aquaculture.

World consumption of seafood continues to rise, but the seas and oceans are already over-exploited. Land-based (saline) aquaculture may offer a sustainable way to meet the growing demand for fish and shellfish. A major problem of aquaculture is nutrient waste, as most of the nutrients added through feed are released into the environment in dissolved form. Wetlands are nature's water purifiers. Constructed wetlands are commonly used to treat contaminated freshwater effluent. Experience with saline systems is more limited. This paper explores the potential of constructed saline wetlands for treating the nutrient-rich discharge from land-based saline aquaculture systems. The primary function of constructed wetlands is water purification, but other ancillary benefits can also be incorporated into treatment wetland designs. Marsh vegetation enhances landscape beauty and plant diversity, and wetlands may offer habitat for fauna and recreational areas. Various approaches can be taken in utilizing plants (halophytes, macro-algae, micro-algae) in the treatment of saline aquaculture effluent. Their strengths and weaknesses are reviewed here, and a conceptual framework is presented that takes into account economic and ecological benefits as well as spatial constraints. Use of the framework is demonstrated for assessing various saline aquaculture systems in the southwestern delta region of the Netherlands.

Salt marsh macrophyte Phragmites australis strategies assessment for its dominance in mercury-contaminated coastal lagoon (Ria de Aveiro, Portugal).

INTRODUCTION AND AIMS: The dominance of a plant species in highly metal-contaminated areas reflects its tolerance or adaptability potential to these scenarios. Hence, plants with high adaptability and/or tolerance to exceptionally high metal-contaminated scenarios may help protect environmental degradation. The present study aimed to assess the strategies adopted by common reed, Phragmites australis for its dominance in highly mercury-contaminated Ria de Aveiro coastal lagoon (Portugal). MATERIALS AND METHODS: Both plant samples and the sediments vegetated by monospecific stand of Phragmites australis were collected in five replicates from mercury-free (reference) and contaminated sites during low tide between March 2006 and January 2007. The sediments' physico-chemical traits, plant dry mass, uptake, partitioning, and transfer of mercury were evaluated during growing season (spring, summer, autumn, and winter) of P. australis. Redox potential and pH of the sediment around roots were measured in situ using a WTW-pH 330i meter. Dried sediments were incinerated for 4 h at 500°C for the estimation of organic matter whereas plant samples were oven-dried at 60°C till constant weight for plant dry mass determination. Mercury concentrations in sediments and plant parts were determined by atomic absorption spectrometry with thermal decomposition, using an advanced mercury analyzer (LECO 254) and maintaining the accuracy and precision of the analytical methodologies. In addition, mercury bioaccumulation and translocation factors were also determined to differentiate the accumulation of mercury and its subsequent translocation to plant parts in P. australis. RESULTS AND CONCLUSIONS: P. australis root exhibited the highest mercury accumulation followed by rhizome and leaves during the reproductive phase (autumn). During the same phase, P. australis exhibited ≈5 times less mercury-translocation factor (0.03 in leaf) when compared with the highest mercury bioaccumulation factor for root (0.14). Moreover, seasonal variations differentially impacted the studied parameters. P. australis' extraordinary ability to (a) pool the maximum mercury in its roots and rhizomes, (b) protect its leaf against mercury toxicity by adopting the mercury exclusion, and (c) adjust the rhizosphere-sediment environment during the seasonal changes significantly helps to withstand the highly mercury-contaminated Ria de Aveiro lagoon. The current study implies that P. australis has enough potential to be used for mercury stabilization and restoration of sediments/soils rich in mercury as well.

Assessment of adaptive evolution between wheat and rice as deduced from full-length common wheat cDNA sequence data and expression patterns.

BACKGROUND: Wheat is an allopolyploid plant that harbors a huge, complex genome. Therefore, accumulation of expressed sequence tags (ESTs) for wheat is becoming particularly important for functional genomics and molecular breeding. We prepared a comprehensive collection of ESTs from the various tissues that develop during the wheat life cycle and from tissues subjected to stress. We also examined their expression profiles in silico. As full-length cDNAs are indispensable to certify the collected ESTs and annotate the genes in the wheat genome, we performed a systematic survey and sequencing of the full-length cDNA clones. This sequence information is a valuable genetic resource for functional genomics and will enable carrying out comparative genomics in cereals. RESULTS: As part of the functional genomics and development of genomic wheat resources, we have generated a collection of full-length cDNAs from common wheat. By grouping the ESTs of recombinant clones randomly selected from the full-length cDNA library, we were able to sequence 6,162 independent clones with high accuracy. About 10% of the clones were wheat-unique genes, without any counterparts within the DNA database. Wheat clones that showed high homology to those of rice were selected in order to investigate their expression patterns in various tissues throughout the wheat life cycle and in response to abiotic-stress treatments. To assess the variability of genes that have evolved differently in wheat and rice, we calculated the substitution rate (Ka/Ks) of the counterparts in wheat and rice. Genes that were preferentially expressed in certain tissues or treatments had higher Ka/Ks values than those in other tissues and treatments, which suggests that the genes with the higher variability expressed in these tissues is under adaptive selection. CONCLUSION: We have generated a high-quality full-length cDNA resource for common wheat, which is essential for continuation of the ongoing curation and annotation of the wheat genome. The data for each clone's expression in various tissues and stress treatments and its variability in wheat and rice as a result of their diversification are valuable tools for functional genomics in wheat and for comparative genomics in cereals.