Disentangling the photochemical salinity tolerance in Aster tripolium L.: connecting biophysical traits with changes in fatty acid composition

Unraveling the physiological responses of morphologically distinct corals to low oxygen

Background

Low oxygen in marine environments, intensified by climate change and local pollution, poses a substantial threat to global marine ecosystems, especially impacting vulnerable coral reefs and causing metabolic crises and bleaching-induced mortality. Yet, our understanding of the potential impacts in tropical regions is incomplete. Furthermore, uncertainty surrounds the physiological responses of corals to hypoxia and anoxia conditions.

Methods

We initially monitored in situ dissolved oxygen (DO) levels at Kham Island in the lower Gulf of Thailand. Subsequently, we conducted a 72-hour experimental exposure of corals with different morphologies-Pocillopora acuta, Porites lutea, and Turbinaria mesenterina-to low oxygen conditions, while following a 12/12-hour dark/light cycle. Three distinct DO conditions were employed: ambient (DO 6.0 ± 0.5 mg L-1), hypoxia (DO 2.0 ± 0.5 mg L-1), and anoxia (DO < 0.5 mg L-1). We measured and compared photosynthetic efficiency, Symbiodiniaceae density, chlorophyll concentration, respiratory rates, primary production, and calcification across the various treatments.

Results

Persistent hypoxia was observed at the study site. Subsequent experiments revealed that low oxygen levels led to a notable decrease in the maximum quantum yield over time in all the species tested, accompanied by declining rates of respiration and calcification. Our findings reveal the sensitivity of corals to both hypoxia and anoxia, particularly affecting processes crucial to energy balance and structural integrity. Notably, P. lutea and T. mesenterina exhibited no mortality over the 72-hour period under hypoxia and anoxia conditions, while P. acuta, exposed to anoxia, experienced mortality with tissue loss within 24 hours. This study underscores species-specific variations in susceptibility associated with different morphologies under low oxygen conditions. The results demonstrate the substantial impact of deoxygenation on coral growth and health, with the compounded challenges of climate change and coastal pollution exacerbating oxygen availability, leading to increasingly significant implications for coral ecosystems.

Mechanistic study on the increase of Microcystin-LR synthesis and release in Microcystis aeruginosa by amino-modified nano-plastics

Ecological risk of micro/nano-plastics (MPs/NPs) has become an important environmental issue. Microcystin-leucine-arginine (MC-LR) produced by Microcystis aeruginosa (M. aeruginosa) is the most common and toxic secondary metabolites (SM). However, the influencing mechanism of MPs and NPs exposure on MC-LR synthesis and release have still not been clearly evaluated. In this work, under both acute (4d) and long-term exposure (10d), only high-concentration (10 mg/L) exposure of amino-modified polystyrene NPs (PS-NH2-NPs) promoted MC-LR synthesis (32.94 % and 42.42 %) and release (27.35 % and 31.52 %), respectively. Mechanistically, PS-NH2-NPs inhibited algae cell density, interrupted pigment synthesis, weakened photosynthesis efficiency, and induced oxidative stress, with subsequent enhancing the MC-LR synthesis. Additionally, PS-NH2-NPs exposure up-regulated MC-LR synthesis pathway genes (mcyA, mcyB, mcyD, and mcyG) combined with significantly increased metabolomics (Leucine and Arginine), thereby enhancing MC-LR synthesis. PS-NH2-NPs exposure enhanced the MC-LR release from M. aeruginosa via up-regulated MC-LR transport pathway genes (mcyH) and the shrinkage of plasma membrane. Our results provide new insights into the long-time coexistence of NPs with algae in freshwater systems might pose a potential threat to aquatic environments and human health.

Oxidative stress and energy metabolic response of Isochrysis galbana induced by different types of pristine and aging microplastics and their leachates

The aging process and leachate composition of different types of MPs (PS, PS-NH2, PS-COOH and PMMA) with a particle size of 1.0 μm were characterized, and marine microalgae Isochrysis galbana OA3011(I. galbana) was used as test organism to investigate the 96 h toxic effects of MPs before and after aging as well as leachate exposure. Except for polymethyl methacrylate (PMMA), all other tested microplastics showed significant aggregation in seawater, which increased with the presence of surface amino and carboxyl groups, in addition, the increase in polymer dispersibility index (PDI) values after aging reflected more severe aggregation. Fourier transform infrared spectrometer (FTIR) showed that the surface amino groups were shed during the aging of PS-NH2, which can likewise be demonstrated by the change in surface electric potential from positive to negative before and after aging. PMMA, due to the addition of plasticizers (HEHP and DIBP detected in high concentration) and its own structure, has stronger resistance to aging than the other three microplastics, and no significant aging phenomenon occurs. As for I. galbana, growth inhibition, oxidative stress and energy metabolism were tested after exposure to different microplastics and their leachate. It was found that high concentrations of A-PS had a greater negative impact on I. galbana, while the toxic effects of PS-NH2 and PS-COOH on I. galbana behaved in a diametrically opposite way before and after aging compared to PS with the inhibitory effect decreasing after aging, which was caused by the shedding of surface groups. As for PMMA, the differences in the toxic effects on microalgae before and after aging were not significant. The inhibitory effect of low concentrations of PAEs (Phthalate acid esters) in the leachate of PS-COOH on I. galbana was not significant, and the stronger inhibitory effect of 4 d L-PS-NH2 was presumed to be the shedding of positively charged groups.

Harnessing the Value of Tripolium pannonicum and Crithmum maritimum Halophyte Biomass through Integrated Green Biorefinery

Bioactive extracts are often the target fractions in bioprospecting, and halophyte plants could provide a potential source of feedstock for high-value applications as a part of integrated biorefineries. Tripolium pannonicum (Jacq.) Dobrocz. (sea aster) and Crithmum maritimum L. (sea fennel) are edible plants suggested for biosaline halophyte-based agriculture. After food production and harvesting of fresh leaves for food, the inedible plant fractions could be utilized to produce extracts rich in bioactive phytochemicals to maximize feedstock application and increase the economic feasibility of biomass processing to bioenergy. This study analyzed fresh juice and extracts from screw-pressed sea aster and sea fennel for their different phenolic compounds and pigment concentrations. Antioxidant and enzyme inhibition activities were also tested in vitro. Extracts from sea aster and sea fennel had phenolic contents up to 45.2 mgGAE/gDM and 64.7 mgGAE/gDM, respectively, and exhibited >70% antioxidant activity in several assays. Ethanol extracts also showed >70% inhibition activity against acetylcholinesterase and >50% inhibition of tyrosinase and α-glucosidase. Therefore, these species can be seen as potential feedstocks for further investigations.

Toxicity effects of polystyrene nanoplastics and arsenite on Microcystis aeruginosa

Despite the increasing research on the fate of nanoplastics (NPs, <100 nm) in freshwater systems, little is known about the joint toxic effects of metal(loid)s and NPs modified with different functional groups on microalgae. Here, we explored the joint toxic effects of two types of polystyrene NPs [one modified with a sulfonic acid group (PSNPs-SO₃H), and one without this functional group (PSNPs)] and arsenic (As) on the microalgae Microcystis aeruginosa. The results highlighted that PSNPs-SO₃H showed a smaller hydrodynamic diameter and greater potential to adsorb positively charged ions than PSNPs, contributing to the more severe growth inhibition, while both of them produced oxidative stress. Metabolomics further revealed that the fatty acid metabolism of the microalgae was significantly up-regulated under both NPs exposure, while PSNPs-SO₃H down-regulated the tricarboxylic acid cycle (TCA cycle) of the microalgae. As uptake by algae was significantly reduced by 82.58 % and 59.65 % in the presence of 100 mg/L PSNPs and PSNPs-SO₃H, respectively. The independent action model showed that the joint toxicity of both NPs with As was assessed as antagonistic. In addition, PSNPs and PSNPs-SO₃H had dissimilar effects on the composition of the microalgae extracellular polymeric substances (EPS), resulting in different uptake and adsorption of As, thereby affecting the physiology and biochemistry of algae. Overall, our findings propose that the specific properties of NPs should be considered in future environmental risk assessments.

Improving Salicornia ramosissima photochemical and biochemical resilience to extreme heatwaves through rhizosphere engineering with Plant Growth-Promoting Bacteria

The anticipated rise in the length, frequency, and intensity of heatwaves (HW) in the Mediterranean region poses a danger to the crops, as these brief but high-intensity thermal stress events halt plant productivity. This arises the need to develop new eco-friendly sustainable strategies to overcome food demand. Halophytes such as Salicornia ramosissima appear as cash crop candidates, alongside with new biofertilization approaches using Plant Growth Promoting Bacteria (PGPB). In the present work, S. ramosissima plants exposed to heatwave (HW) treatments with and without marine PGPB inoculation is studied to evaluate the physiological responses behind eventual thermal adaptation conditions. Plants exposed to HW inoculated with ACC deaminase and IAA-producing PGPB showed a 50% reduction in the photochemical energy dissipation, when compared to their non-inoculated counterparts, indicating higher light-use efficiency. The observed concomitant increase (76-234%) in several pigments indicates improved inoculated HW-exposed individuals' light harvesting and photoprotection under stressful conditions. This reduction of the physiological stress levels in inoculated plants was also evident by the significant reduction of several antioxidant enzymes as well as of membrane lipid peroxidation products. Additionally, improved membrane stability could also be observed, through the regulation of fatty acid unsaturation levels, decreasing the excessive fluidity imposed by HW treatment. All these improved physiological traits associated with specific PGP traits highlight a key potential of the use of these PGPB consortiums as biofertilizers for S. ramosissima cash crop production in the Mediterranean, where increasing frequency in HW-events is a major drawback to plant production, even to warm-climate plants.

Santos S, Janeiro Sequeira R, Mateos-Naranjo E, Rodríguez-Llorente ID, Pajuelo E, Redondo-Gómez S, Matos AR, Mesa-Marín J, Figueiredo A, Duarte B. Improving Grapevine Heat Stress Resilience with Marine Plant Growth-Promoting Rhizobacteria Consortia

Amid climate change, heatwave events are expected to increase in frequency and severity. As a result, yield losses in viticulture due to heatwave stress have increased over the years. As one of the most important crops in the world, an eco-friendly stress mitigation strategy is greatly needed. The present work aims to evaluate the physiological fitness improvement by two marine plant growth-promoting rhizobacteria consortia in Vitis vinifera cv. Antão Vaz under heatwave conditions. To assess the potential biophysical and biochemical thermal stress feedback amelioration, photochemical traits, pigment and fatty acid profiles, and osmotic and oxidative stress biomarkers were analysed. Bioaugmented grapevines exposed to heatwave stress presented a significantly enhanced photoprotection capability and higher thermo-stability, exhibiting a significantly lower dissipation energy flux than the non-inoculated plants. Additionally, one of the rhizobacterial consortia tested improved light-harvesting capabilities by increasing reaction centre availability and preserving photosynthetic efficiency. Rhizobacteria inoculation expressed an osmoprotectant promotion, revealed by the lower osmolyte concentration while maintaining leaf turgidity. Improved antioxidant mechanisms and membrane stability resulted in lowered lipid peroxidation product formation when compared to non-inoculated plants. Although the consortia were found to differ significantly in their effectiveness, these findings demonstrate that bioaugmentation induced significant heatwave stress tolerance and mitigation. This study revealed the promising usage of marine PGPR consortia to promote plant fitness and minimize heatwave impacts in grapevines.

Interactive Temperature and CO2 Rise, Salinity, Drought, and Bacterial Inoculation Alter the Content of Fatty Acids, Total Phenols, and Oxalates in the Edible Halophyte Salicornia ramosissima

In this work, we studied the combined effect of increased temperature and atmospheric CO₂, salt and drought stress, and inoculation with plant-growth-promoting rhizobacteria (PGPR) on the growth and some nutritional parameters of the edible halophyte Salicornia ramosissima. We found that the increase in temperature and atmospheric CO₂, combined with salt and drought stresses, led to important changes in S. ramosissima fatty acids (FA), phenols, and oxalate contents, which are compounds of great importance for human health. Our results suggest that the S. ramosissima lipid profile will change in a future climate change scenario, and that levels of oxalate and phenolic compounds may change in response to salt and drought stress. The effect of inoculation with PGPR depended on the strains used. Some strains induced the accumulation of phenols in S. ramosissima leaves at higher temperature and CO₂ while not altering FA profile but also led to an accumulation of oxalate under salt stress. In a climate change scenario, a combination of stressors (temperature, salinity, drought) and environmental conditions (atmospheric CO_2, PGPR) will lead to important changes in the nutritional profiles of edible plants. These results may open new perspectives for the nutritional and economical valorization of S. ramosissima.

Light harvesting regulation: A versatile network of key components operating under various stress conditions in higher plants

Light harvesting is finetuned through two main strategies controlling energy transfer to the reaction centers of photosystems: i) regulating the amount of light energy at the absorption level, ii) regulating the amount of the absorbed energy at the utilization level. The first strategy is ensured by changes in the cross-section, i.e., the size of the photosynthetic antenna. These changes can occur in a short-term (state transitions) or long-term way (changes in antenna protein biosynthesis) depending on the light conditions. The interrelation of these two ways is still underexplored. Regulating light absorption through the long-term modulation of photosystem II antenna size has been mostly considered as an acclimatory mechanism to light conditions. The present review highlights that this mechanism represents one of the most versatile mechanisms of higher plant acclimation to various conditions including drought, salinity, temperature changes, and even biotic factors. We suggest that H₂O₂ is the universal signaling agent providing the switch from the short-term to long-term modulation of photosystem II antenna size under these factors. The second strategy of light harvesting is represented by redirecting energy to waste mainly via thermal energy dissipation in the photosystem II antenna in high light through PsbS protein and xanthophyll cycle. In the latter case, H₂O₂ also plays a considerable role. This circumstance may explain the maintenance of the appropriate level of zeaxanthin not only upon high light but also upon other stress factors. Thus, the review emphasizes the significance of both strategies for ensuring plant sustainability under various environmental conditions.

Effects of Hypoxia on Coral Photobiology and Oxidative Stress

Global ocean oxygen (O2) content is decreasing as climate change drives declines in oxygen solubility, strengthened stratification of seawater masses, increased biological oxygen consumption and coastal eutrophication. Studies on the biological effects of nocturnal decreased oxygen concentrations (hypoxia) on coral reefs are very scarce. Coral reefs are fundamental for supporting one quarter of all marine species and essential for around 275 million people worldwide. This study investigates acute physiological and photobiological responses of a scleractinian coral (Acropora spp.) to overnight hypoxic conditions (<2 mg/L of O2). Bleaching was not detected, and visual and physical aspects of corals remained unchanged under hypoxic conditions. Most photobiological-related parameters also did not show significant changes between treatments. In addition to this, no significant differences between treatments were observed in the pigment composition. However, hypoxic conditions induced a significant decrease in coral de-epoxidation state of the xanthophyll cycle pigments and increase in DNA damage. Although the present findings suggest that Acropora spp. is resilient to some extent to short-term daily oxygen oscillations, long-term exposure to hypoxia, as predicted to occur with climate change, may still have deleterious effects on corals.

Chemical Profiling of Limonium vulgare Mill. Using UHPLC-DAD-ESI/MS2 and GC-MS Analysis

Limonium vulgare Mill. is a plant growing widely in harsh environments, such as salt marshes, for which a chemical profile is still unknown, although some interesting bioactivities were already reported. So, this halophyte chemical profile must be established to find the possible bioactive compounds, valorize the species, and contribute to the salt marsh’s exploitation. This work set the chemical profile of L. vulgare’s aerial parts (leaves and inflorescences) using UHPLC-DAD-ESI/MS2 and GC-MS analysis. The lipophilic profile showed a richness in fatty acids, alkanes, and terpenoids, β-sitosterol being the major compound in inflorescences in the fruiting stage (0.822 ± 0.015 mg/g of the dry plant) and leaves (0.534 ± 0.017 mg/g of the dry plant). In contrast, in the inflorescences in the flowering stage, the major compound is nonacosane (0.228 ± 0.001 mg/g of the dry plant). The polyphenolic profile demonstrates that L. vulgare produces several flavonoids from which quercetin and myricetin can be highlighted; in particular, myricetin derivatives are prevalent in all extracts. Amongst the flavonoids, myricetin 3-rhamnoside is the most abundant in the inflorescences in the flowering stage (6.35 ± 0.05 mg/g of the dry plant), myricetin in leaves (9.69 ± 0.11 mg/g of the dry plant), and in the inflorescences in the fruiting stage baicalin presents the highest amount (5.15 ± 0.07 mg/g of the dry plant). This is the first report on L. vulgare’s chemical profile and the results indicate that this species is an exciting source of bioactive compounds, suggesting it has a use to produce nutraceuticals and/or pharmaceuticals.

Ocean Acidification Alleviates Dwarf Eelgrass (Zostera noltii) Lipid Landscape Remodeling under Warming Stress

Coastal seagrass meadows provide a variety of essential ecological and economic services, including nursery grounds, sediment stabilization, nutrient cycling, coastal protection, and blue carbon sequestration. However, these ecosystems are highly threatened by ongoing climatic change. This study was aimed to understand how the dwarf eelgrass Zostera noltii leaf lipid landscapes are altered under predicted ocean warming (+4 °C) and hypercapnic (ΔpH 0.4) conditions. Warming and hypercapnic conditions were found to induce a severe reduction in the leaf total fatty acid, though the combined treatment substantially alleviated this depletion. The lipid discrimination revealed a significant increase in the relative monogalactosyldiacylglycerol (MGDG) content in both hypercapnic and warming conditions, allied to plastidial membrane stabilization mechanisms. Hypercapnia also promoted enhanced phosphatidylglycerol (PG) leaf contents, a mechanism often associated with thylakoid reinvigoration. In addition to changing the proportion of storage, galacto- and phospholipids, the tested treatments also impacted the FA composition of all lipid classes, with warming exposure leading to decreases in polyunsaturated fatty acids (PUFAs); however, the combination of both stress conditions alleviated this effect. The observed galactolipid and phospholipid PUFA decreases are compatible with a homeoviscous adaptation, allowing for the maintenance of membrane stability by counteracting excessive membrane fluidity. Neutral lipid contents were substantially increased under warming conditions, especially in C18 fatty acids (C18), impairing their use as substrates for fatty acylated derivatives essential for maintaining the osmotic balance of cells. An analysis of the phospholipid and galactolipid fatty acid profiles as a whole revealed a higher degree of discrimination, highlighting the higher impact of warming and the proposed stress alleviation effect induced by increased water-dissolved CO2 availability. Still, it is essential to remember that the pace at which the ocean is warming can overcome the ameliorative capacity induced by higher CO2 availability, leaving seagrasses under severe heat stress beyond their lipid remodeling capacity.

Bioaugmentation Improves Phytoprotection in Halimione portulacoides Exposed to Mild Salt Stress: Perspectives for Salinity Tolerance Improvement

Plant growth-promoting rhizobacteria (PGPR) can promote plant growth through mechanisms such as mineral phosphates solubilization, biological N2 fixation and siderophores and phytohormones production. The present work aims to evaluate the physiological fitness improvement by PGPR in Halimione portulacoides under mild and severe salt stress. PGPR-inoculated plants showed improved energy use efficiencies, namely in terms of the trapped and electron transport energy fluxes, and reduced energy dissipation. Allied to this, under mild stress, inoculated plants exhibited a significant reduction of the Na and Cl root concentrations, accompanied by a significant increase in K and Ca leaf content. This ion profile reshaping was intrinsically connected with an increased leaf proline content in inoculated plants. Moreover, bioaugmented plants showed an increased photoprotection ability, through lutein and zeaxanthin leaf concentration increase, allowing plants to cope with potentially photoinhibition conditions. Reduced Na leaf uptake in inoculated plants, apparently reduced the oxidative stress degree as observed by the superoxide dismutase and peroxidase activity reduction. Additionally, a reduced lipid peroxidation degree was observed in inoculated plants, while compared to their non-inoculated counterparts. These results, point out an important role of bioaugmentation in promoting plant fitness and improving salt tolerance, with a great potential for applications in biosaline agriculture and salinized soil restoration.

Salinity Modulates Juncus acutus L. Tolerance to Diesel Fuel Pollution

Soil contamination with petroleum-derived substances such as diesel fuel has become a major environmental threat. Phytoremediation is one of the most studied ecofriendly low-cost solutions nowadays and halophytes species has been proved to have potential as bio-tools for this purpose. The extent to which salinity influences diesel tolerance in halophytes requires investigation. A greenhouse experiment was designed to assess the effect of NaCl supply (0 and 85 mM NaCl) on the growth and photosynthetic physiology of Juncus acutus plants exposed to 0, 1 and 2.5% diesel fuel. Relative growth rate, water content and chlorophyll a derived parameters were measured in plants exposed to the different NaCl and diesel fuel combinations. Our results indicated that NaCl supplementation worsened the effects of diesel toxicity on growth, as diesel fuel at 2.5% reduced relative growth rate by 25% in the absence of NaCl but 80% in plants treated with NaCl. Nevertheless, this species grown at 0 mM NaCl showed a high tolerance to diesel fuel soil presence in RGR but also in chlorophyll fluorescence parameters that did not significantly decrease at 1% diesel fuel concentration in absence of NaCl. Therefore, this study remarked on the importance of knowing the tolerance threshold to abiotic factors in order to determine the bioremediation capacity of a species for a specific soil or area. In addition, it showed that NaCl presence even in halophytes does not always have a positive effect on plant physiology and it depends on the pollutant nature.

Mechanisms of Salt Tolerance and Molecular Breeding of Salt-Tolerant Ornamental Plants

As the area of salinized soils increases, and freshwater becomes more scarcer worldwide, an urgent measure for agricultural production is to use salinized land and conserve freshwater resources. Ornamental flowering plants, such as carnations, roses, chrysanthemums, and gerberas, are found around the world and have high economic, ornamental, ecological, and edible value. It is therefore prudent to improve the salt tolerance of these important horticultural crops. Here, we summarize the salt-adaptive mechanisms, genes, and molecular breeding of ornamental flowering crops. We also review the genome editing technologies that provide us with the means to obtain novel varieties with high salinity tolerance and improved utility value, and discuss future directions of research into ornamental plants like salt exclusion mechanism. We considered that the salt exclusion mechanism in ornamental flowering plants, the acquisition of flowers with high quality and novel color under salinity condition through gene editing techniques should be focused on for the future research.

Potential of Asparagopsis armata as a Biopesticide for Weed Control under an Invasive Seaweed Circular-Economy Framework

Simple Summary

The invasive seaweed Asparagopsis armata has the potential to be used as a biopesticide. The application of its exudate shows severe impacts on energetic and carotenoid metabolism and induces significant oxidative stress in a model weed. This points to the potential use of this macroalga as a resource for a biopesticide cocktail, for sustainable and eco-friendly weed control and as a substitute for the chemical pesticides widely used nowadays.

Abstract

Marine macroalgae have been increasingly targeted as a source of bioactive compounds to be used in several areas, such as biopesticides. When harvesting invasive species, such as Asparagopsis armata, for this purpose, there is a two-folded opportunity: acquiring these biomolecules from a low-cost resource and controlling its spreading and impacts. The secondary metabolites in this seaweed’s exudate have been shown to significantly impact the physiology of species in the ecosystems where it invades, indicating a possible biocidal potential. Considering this in the present work, an A. armata exudate cocktail was applied in the model weed Thellungiella halophila to evaluate its physiological impact and mode of action, addressing its potential use as a natural biocide. A. armata greatly affected the test plants’ physiology, namely, their photochemical energy transduction pathway (impairing light-harvesting and chemical energy production throughout the chloroplast electron transport chain), carotenoid metabolism and oxidative stress. These mechanisms of action are similar to the ones triggered when using the common chemical pesticides, highlighting the potential of the A. armata exudate cocktail as an eco-friendly biopesticide.

Membrane remodelling and triacylglycerol accumulation in drought stress resistance: The case study of soybean phospholipases A

Agriculture is facing major constraints with the increase of global warming, being drought a major factor affecting productivity. Soybean (Glycine max) is among the most important food crops due to the high protein and lipid content of its seeds despite being considerably sensitive to drought. Previous knowledge has shown that drought induces a severe modulation in lipid and fatty acid content of leaves, related to alteration of membrane structure by lipolytic enzymes and activation of signalling pathways. In that sense, little is known on lipid modulation and lipolytic enzymes' role in soybean drought stress tolerance. In this work, we present for the first time, soybean leaves lipid content modulation in several drought stress levels, highlighting the involvement of phospholipases A. Moreover, a comprehensive analysis of the phospholipase A superfamily was performed, where 53 coding genes were identified and 7 were selected to gene expression analysis in order to elucidate their role in soybean lipid modulation under water deficit. Proportionally to the drought severity, our results revealed that galactolipids relative abundance and their content in linolenic acid decrease. At the same time an accumulation of neutral lipids, mainly due to triacylglycerol content increase, as well as their content in linolenic acid, is observed. Overall, PLA gene expression regulation and lipid modulation corroborate the hypothesis that phospholipases A may be channelling the plastidial fatty acids into extraplastidial lipids leading to a drought-induced accumulation of triacylglycerol in soybean leaves, a key feature to cope with water stress.

Heavy Metal Pre-Conditioning History Modulates Spartina patens Physiological Tolerance along a Salinity Gradient

Land salinization, resulting from the ongoing climate change phenomena, is having an increasing impact on coastal ecosystems like salt marshes. Although halophyte species can live and thrive in high salinities, they experience differences in their salt tolerance range, being this a determining factor in the plant distribution and frequency throughout marshes. Furthermore, intraspecific variation to NaCl response is observed in high-ranging halophyte species at a population level. The present study aims to determine if the environmental history, namely heavy metal pre-conditioning, can have a meaningful influence on salinity tolerance mechanisms of Spartina patens, a highly disperse grass invader in the Mediterranean marshes. For this purpose, individuals from pristine and heavy metal contaminated marsh populations were exposed to a high-ranging salinity gradient, and their intraspecific biophysical and biochemical feedbacks were analyzed. When comparing the tolerance mechanisms of both populations, S. patens from the contaminated marsh appeared to be more resilient and tolerant to salt stress, this was particularly present at the high salinities. Consequently, as the salinity increases in the environment, the heavy metal contaminated marsh may experience a more resilient and better adapted S. patens community. Therefore, the heavy metal pre-conditioning of salt mash populations appears to be able to create intraspecific physiological variations at the population level that can have a great influence on marsh plant distribution outcome.

Climate Change Impacts on Salt Marsh Blue Carbon, Nitrogen and Phosphorous Stocks and Ecosystem Services

Salt marshes are valuable ecosystems, as they provide food, shelter, and important nursery areas for fish and macroinvertebrates, and a wide variety of ecosystem services for human populations. These ecosystem services heavily rely on the floristic composition of the salt marshes with different species conferring different service values and different adaptation and resilience capacities towards ecosystem stressors. Blue carbon, nitrogen, and phosphorous stocks are no exception to this, and rely on the interspecific differences in the primary production metabolism and physiological traits. Furthermore, these intrinsic physiological characteristics also modulate the species response to any environmental stressor, such as the ones derived from ongoing global changes. This will heavily shape transitional ecosystem services, with significant changes of the ecosystem value of the salt marshes in terms of cultural, provisioning, regulating, and supporting ecosystem services, with a special emphasis on the possible alterations of the blue carbon, nitrogen, and phosphorous stocks retained in these key environments. Thus, the need to integrate plant physiological characteristics and feedbacks towards the expected climate change-driven stressors becomes evident to accurately estimate the ecosystem services of the salt marsh community, and transfer these fundamental services into economic assets, for a fluid communication of the ecosystems value to stakeholders, decision and policy makers, and environmental management entities.

Iberian Halophytes as Agroecological Solutions for Degraded Lands and Biosaline Agriculture

Research on biosaline agriculture has been increasing worldwide in recent years. In this respect, the Iberian halophyte diversity present a high-value ecological solution to be implemented for biosaline-based agroecosystems. The research on these halophytic species has been increasing worldwide and, in the recent years, especially in terms saline agriculture adaptation, osmophysiology and nutraceutical potential, highlighting the importance and potential of these species in terms of agrosolutions. The Mediterranean area has high biodiversity in terms of endemic halophytic vegetation (ca. 62 species), providing an alternative pool of potential new agricultural products to be cultivated in adverse conditions. Besides being highly diverse, most of these species are endemic and present a perennial life cycle with several applications in terms of food, forage, nutraceutical, feedstock and remediation. More specifically, the Iberian halophytic flora shows potential as resources of essential fatty acids, minerals and antioxidants—all very important for human and animal nutrition. Alongside the establishment of halophyte agroecological solutions is the provision of key ecosystem services, such as carbon sequestration and soil rehabilitation. Moreover, halophyte-based ecosystems provide additional recognized ecosystem services, beyond the final product production, by improving soil health, ecosystem biodiversity and storing large amounts of carbon, thereby increasing the ecosystem resilience to climate change and offering a green solution against climate change.

Lipids Composition in Plant Membranes

The paper focuses on the selected plant lipid issues. Classification, nomenclature, and abundance of fatty acids was discussed. Then, classification, composition, role, and organization of lipids were displayed. The involvement of lipids in xantophyll cycle and glycerolipids synthesis (as the most abundant of all lipid classes) were also discussed. Moreover, in order to better understand the biomembranes remodeling, the model (artificial) membranes, mimicking the naturally occurring membranes are employed and the survey on their composition and application in different kind of research was performed. High level of lipids remodeling in the plant membranes under different environmental conditions, e.g., nutrient deficiency, temperature stress, salinity or drought was proved. The key advantage of lipid research was the conclusion that lipids could serve as the markers of plant physiological condition and the detailed knowledge on lipids chemistry will allow to modify their composition for industrial needs.

Lipid landscape remodelling in Sarcocornia fruticosa green and red physiotypes

Under certain abiotic conditions (elevated irradiance, temperature and sediment salinity) observed mostly during the Mediterranean summer, the halophyte Sarcocornia fruticosa suffers a metabolic shift evidenced by a red coloration, evidencing the presence of two physiotypes (green and red). Previous works indicated that this metabolic shift has severe implications in the primary photochemistry of this species, impairing the light and carbon harvesting. Under stress plants have lower light use efficiencies and are more prone to photoinhibition, and thus this metabolic shift is essential for this species to deal with the high light intensities characteristic from this time of the year. Nevertheless, the fatty acid and lipid remodelling in green and red S. fruticosa physiotypes was not previously evaluated nor its relations with this metabolic shift. The evaluation of the lipid landscape suggests several lipid and fatty acid remodelling when comparing both red and green physiotype, as strategies to overcome stress. The galactolipids of the red physiotype suffer several changes aiming to keep chloroplast membrane structural and functional stability during water stress and can also be related to an improvement of the plants response to osmotic stress. At the phospholipid level, a readjustment of its fatty acid profiles was also observable. This remodelling allows the plants to adjust membrane fluidity the imposed osmotic stress, being this action transversal to choroplastidial, extraplastidial, and involves the action of the different phospholipids. Additionally, neutral lipids (NLs) also appear to play a role in osmotic stress adaptation, with an increase content in C18 fatty acids in the red physiotype. The resulting lipid landscape in both physiotypes presents very specific signatures that can be used as biomarkers to track this kind of metabolic shifts, in future studies with similar species.

Marine heat waves alter gene expression of key enzymes of membrane and storage lipids metabolism in Phaeodactylum tricornutum

Across the globe, heat waves are getting more intense and frequent. Diatoms are a major group of microalgae at the base of the marine food webs and an important source of long chain polyunsaturated fatty acids that are transferred through the food web. The present study investigates the possible impacts of temperature increase on lipid classes and expression of genes encoding enzymes related to lipid metabolism in Phaeodactylum tricornutum. The heat wave exposure caused an increase in the relative amounts of plastidial lipids such as the glycolipids monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG) and sulphoquinovosyldiacylglycerol (SQDG) in parallel with a decrease in the neutral lipid fraction, which includes triacylglycerols. In agreement, gene expression analyses revealed an up-regulation of a gene encoding one MGDG synthase and down-regulation of a diacylglycerol acyltransferase (DGAT), a key enzyme in triacylglycerol synthesis. Our results show that heat waves not only negatively impact the abundance of unsaturated fatty acids such as eicosapentaenoic acid (20:5n-3, EPA) and hexadecatrienoic acid (16:3n-4) as observed by the decrease in their relative abundance in MGDG and neutral lipids, respectively, but also induce changes in the relative amounts of the diverse membrane lipids as well as the proportion of membrane/storage lipids. The expression study of key genes indicates that some of the aforementioned alterations are regulated at the transcription level whereas others appear to be post-transcriptional. The changes observed in plastidial lipids are related to negative impacts on the photosynthesis.

Photobiological and lipidic responses reveal the drought tolerance of Aster tripolium cultivated under severe and moderate drought: Perspectives for arid agriculture in the mediterranean

In the past Aster tripolium has already proved to be a good candidate for saline agriculture in soils with low water availability. Thus, the aim of the present work was to disentangle the photobiological and biochemical mechanisms underlying the response of A. tripolium to PEG-induced drought stress, by exposing plants to PEG-induced moderate and severe drought conditions. Plant primary productivity was maintained under moderate drought conditions, due to the presence of alternative electron donors fueling the PSII. Additionally, the high anthocyanin production under drought conditions, act as photoprotective shields against photoinhibition. Moreover, the increased quinone turnover rate simultaneously with a net rate of RC closure and density increase, acted as a counteractive measure, allowing high energy fluxes into the photosystems under drought conditions. PSI showed an activity reduction, indicating that under drought conditions the ETC activity acts as an energetic escape route. Furthermore, membrane remodeling could also be observed under drought. The total fatty acid and omega-3 linolenic acid (18:3) contents were maintained, under osmotic stress. Membrane restructuring with lower amounts of polyunsaturated fatty acids (18:3) is considered an adaptation to osmotically stressful environments. Increased 18:1 and 16:1t fatty acids production improve the LHCs and chloroplast membrane stabilization, allowing the LHC to maintain its efficient functioning. The results here presented are very similar to the ones observed in the past regarding A. tripolium feedback to salinity stress, indicating that the mechanisms to overcome osmotic stress, either due to increased salinity or reduced water availability, are the same.

Fluoxetine Arrests Growth of the Model Diatom Phaeodactylum tricornutum by Increasing Oxidative Stress and Altering Energetic and Lipid Metabolism

Pharmaceutical residues impose a new and emerging threat to aquatic environments and its biota. One of the most commonly prescribed pharmaceuticals is the antidepressant fluoxetine, a selective serotonin re-uptake inhibitor that has been frequently detected, in concentrations up to 40 μg L^–1, in aquatic ecosystems. The present study aims to investigate the ecotoxicity of fluoxetine at environmentally relevant concentrations (0.3, 0.6, 20, 40, and 80 μg L^–1) on cell energy and lipid metabolism, as well as oxidative stress biomarkers in the model diatom Phaeodactylum tricornutum. Exposure to higher concentrations of fluoxetine negatively affected cell density and photosynthesis through a decrease in the active PSII reaction centers. Stress response mechanisms, like β-carotene (β-car) production and antioxidant enzymes [superoxide dismutase (SOD) and ascorbate peroxidase (APX)] up-regulation were triggered, likely as a positive feedback mechanism toward formation of fluoxetine-induced reactive oxygen species. Lipid peroxidation products increased greatly at the highest fluoxetine concentration whereas no variation in the relative amounts of long chain polyunsaturated fatty acids (LC-PUFAs) was observed. However, monogalactosyldiacylglycerol-characteristic fatty acids such as C16:2 and C16:3 increased, suggesting an interaction between light harvesting pigments, lipid environment, and photosynthesis stabilization. Using a canonical multivariate analysis, it was possible to evaluate the efficiency of the application of bio-optical and biochemical techniques as potential fluoxetine exposure biomarkers in P. tricornutum. An overall classification efficiency to the different levels of fluoxetine exposure of 61.1 and 88.9% were obtained for bio-optical and fatty acids profiles, respectively, with different resolution degrees highlighting these parameters as potential efficient biomarkers. Additionally, the negative impact of this pharmaceutical molecule on the primary productivity is also evident alongside with an increase in respiratory oxygen consumption. From the ecological point of view, reduction in diatom biomass due to continued exposure to fluoxetine may severely impact estuarine and coastal trophic webs, by both a reduction in oxygen primary productivity and reduced availability of key fatty acids to the dependent heterotrophic upper levels.

Sarcocornia fruticosa photosynthetic response to short-term extreme temperature events in combination with optimal and sub-optimal salinity concentrations

Climate change would increase frequency and intensity of extreme events as heat and cold waves. There is a lack of studies that consider the co-occurrence of these waves with other abiotic factors relevant on a climate change scenario as salinity. Therefore, it could be interesting to improve our knowledge about the effects that this co-occurrence could have in different species due to the species specific effect of the photosynthesis tolerance to extreme temperatures. A controlled condition experiment was performed using the salt marsh species Sarcocornia perrnis with eight experimental blocks combining temperature ranges (40-28/22-15/13-5 °C) and salinity concentration on the growth solution (171/1050 mM NaCl). After 3 days of treatment, gas exchange, chlorophyll a fluorescence, pigment profile and water state measurement were applied. Photosynthetic machinery function of this perennial species decreased on for both high and low temperature range. Nevertheless, at 13-5 °C the effect of the salinity was mainly due to diffusion limitations more than to damage on the photosystems. At 40-28 °C, in presence of optimal salinity S. fruticosa was not altered overall. However, high temperatures in combination with high salinity reduced the photosynthetic capacity mainly by reducing the efficiency of the electron transport chain.

CO2 uptake and chlorophyll a fluorescence of Suaeda fruticosa grown under diurnal rhythm and after transfer to continuous dark

Although only 2-4% of absorbed light is emitted as chlorophyll (Chl) a fluorescence, its measurement provides valuable information on photosynthesis of the plant, particularly of Photosystem II (PSII) and Photosystem I (PSI). In this paper, we have examined photosynthetic parameters of Suaeda fruticosa L. (family: Amaranthaceae), surviving under extreme xerohalophytic conditions, as influenced by diurnal rhythm or continuous dark condition. We report here CO₂ gas exchange and the kinetics of Chl a fluorescence of S. fruticosa, made every 3 hours (hrs) for 3 days, using a portable infra-red gas analyzer and a Handy PEA fluorimeter. Our measurements on CO₂ gas exchange show the maximum rate of photosynthesis to be at 08:00 hrs under diurnal condition and at 05:00 hrs under continuous dark. From the OJIP phase of Chl a fluorescence transient, we have inferred that the maximum quantum yield of PSII photochemistry must have increased during the night under diurnal rhythm, and between 11:00 and 17:00 hrs under constant dark. Overall, our study has revealed novel insights into how photosynthetic reactions are affected by the photoperiodic cycles in S. fruticosa under high salinity. This study has further revealed a unique strategy operating in this xero-halophyte where the repair mechanism for damaged PSII operates during the dark, which, we suggest, contributes to its ecological adaptation and ability to survive and reproduce under extreme saline, high light, and drought conditions. We expect these investigations to help in identifying key genes and pathways for raising crops for saline and dry areas.

Early Brassica Crops Responses to Salinity Stress: A Comparative Analysis Between Chinese Cabbage, White Cabbage, and Kale

Soil salinity is severely affecting crop productivity in many countries, particularly in the Mediterranean area. To evaluate early plant responses to increased salinity and characterize tolerance markers, three important Brassica crops - Chinese cabbage (Brassica rapa ssp. pekinensis), white cabbage (B. oleracea var. capitata) and kale (B. oleracea var. acephala) were subjected to short-term (24 h) salt stress by exposing them to NaCl at concentrations of 50, 100, or 200 mM. Physiological (root growth, photosynthetic performance parameters, and Na+/K+ ratio) and biochemical parameters (proline content and lipid peroxidation as indicated by malondialdehyde, MDA, levels) in the plants' roots and leaves were then measured. Photosynthetic parameters such as the total performance index PItotal (describing the overall efficiency of PSI, PSII and the intersystem electron transport chain) appeared to be the most salinity-sensitive parameter and informative stress marker. This parameter was decreased more strongly in Chinese cabbage than in white cabbage and kale. It indicated that salinity reduced the capacity of the photosynthetic system for efficient energy conversion, particularly in Chinese cabbage. In parallel with the photosynthetic impairments, the Na+/K+ ratio was highest in Chinese cabbage leaves and lowest in kale leaves while kale root is able to keep high Na+/K+ ratio without a significant increase in MDA. Thus Na+/K+ ratio, high in root and low in leaves accompanying with low MDA level is an informative marker of salinity tolerance. The crops' tolerance was positively correlated with levels of the stress hormone abscisic acid (ABA) and negatively correlated with levels of jasmonic acid (JA), and jasmonoyl-L-isoleucine (JA-Ile). Furthermore, salinity induced contrasting changes in levels of the growth-promoting hormones brassinosteroids (BRs). The crop's tolerance was positively correlated with levels of BR precursor typhasterol while negatively with the active BR brassinolide. Principal Component Analysis revealed correlations in observed changes in phytohormones, biochemical, and physiological parameters. Overall, the results show that kale is the most tolerant of the three species and Chinese cabbage the most sensitive to salt stress, and provide holistic indications of the spectrum of tolerance mechanisms involved.

Study of the Persistence of the Phytotoxicity Induced by Graphene Oxide Quantum Dots and of the Specific Molecular Mechanisms by Integrating Omics and Regular Analyses

Although increasing attention has been paid to the nanotoxicity of graphene oxide quantum dots (GOQDs) due to their broad range of applications, the persistence and recoverability associated with GOQDs had been widely ignored. Interestingly, stress-response hormesis for algal growth was observed for Chlorella vulgaris as a single-celled model organism. Few physiological parameters, such as algal density, plasmolysis, and levels of reactive oxygen species, exhibited facile recovery. In contrast, the effects on chlorophyll a levels, permeability, and starch grain accumulation exhibited persistent toxicity. In the exposure stage, the downregulation of genes related to unsaturated fatty acid biosynthesis, carotenoid biosynthesis, phenylpropanoid biosynthesis, and binding contributed to toxic effects on photosynthesis. In the recovery stage, downregulation of genes related to the cis-Golgi network, photosystem I, photosynthetic membrane, and thylakoid was linked to the persistence of toxic effects on photosynthesis. The upregulated galactose metabolism and downregulated aminoacyl-tRNA biosynthesis also indicated toxicity persistence in the recovery stage. The downregulation and upregulation of phenylalanine metabolism in the exposure and recovery stages, respectively, reflected the tolerance of the algae to GOQDs. The present study highlights the importance of studying nanotoxicity by elucidation of stress and recovery patterns with metabolomics and transcriptomics.

Ecotoxicity of the lipid-lowering drug bezafibrate on the bioenergetics and lipid metabolism of the diatom Phaeodactylum tricornutum

Pharmaceutical residues impose a new and emerging threat to the marine environment and its biota. In most countries, ecotoxicity tests are not required for all pharmaceutical residues classes and, even when mandatory, these tests are not performed using marine primary producers such as diatoms. These microalgae are among the most abundant class of primary producers in the marine realm and key players in the marine trophic web. Blood-lipid-lowering agents such as bezafibrate and its derivatives are among the most prescribed drugs and most frequently found human pharmaceuticals in aquatic environments. The present study aims to investigate the bezafibrate ecotoxicity and its effects on primary productivity and lipid metabolism, at environmentally relevant concentrations, using the model diatom Phaeodactylum tricornutum. Under controlled conditions, diatom cultures were exposed to bezafibrate at 0, 3, 6, 30 and 60 μg L^-1, representing concentrations that can be found in the vicinity of discharges of wastewater treatment plants. High bezafibrate concentrations increased cell density and are suggested to promote a shift from autotrophic to mixotrophic metabolism, with diatoms using light energy generated redox potential to breakdown bezafibrate as carbon source. This was supported by an evident increase in cell density coupled with an impairment of the thylakoid electron transport and consequent photosynthetic activity reduction. In agreement, the concentrations of plastidial marker fatty acids showed negative correlations and Canonical Analysis of Principal coordinates of the relative abundances of fatty acid and photochemical data allowed the separation of controls and cells exposed to bezafibrate with high classification efficiency, namely for photochemical traits, suggesting their validity as suitable biomarkers of bezafibrate exposure. Further evaluations of the occurrence of a metabolic shift in diatoms due to exposure to bezafibrate is paramount, as ultimately it may reduce O₂ generation and CO₂ fixation in aquatic ecosystems with ensuing consequences for neighboring heterotrophic organisms.

Investigating the physiological mechanisms underlying Salicornia ramosissima response to atmospheric CO2 enrichment under coexistence of prolonged soil flooding and saline excess

A 45-days long climatic chamber experiment was design to evaluate the effect of 400 and 700 ppm atmospheric CO₂ treatments with and without soil water logging in combination with 171 and 510 mM NaCl in the halophyte Salicornia ramosissima. In order to ascertain the possible synergetic impact of these factors associate to climatic change in this plant species physiological and growth responses. Our results indicated that elevated atmospheric CO₂ concentration improved plant physiological performance under suboptimal root-flooding and saline conditions plants. Thus, this positive impact was mainly ascribed to an enhancement of energy transport efficiency, as indicated the greater P_G, N and Sm values, and the maintaining of carbon assimilation capacity due to the higher net photosynthetic rate (A_N) and water use efficiency (_iWUE). This could contribute to reduce the risk of oxidative stress owing to the accumulation of reactive oxygen species (ROS). Moreover, plants grown at 700 ppm had a greater capacity to cope with flooding and salinity synergistic impact by a greater efficiency in the modulation in enzyme antioxidant machinery and by the accumulation of osmoprotective compounds and saturated fatty acids in its tissues. These responses indicate that atmospheric CO₂ enrichment would contribute to preserve the development of Salicornia ramosissima against the ongoing process of increment of soil stressful conditions linked with climatic change.

Impact of short-term extreme temperature events on physiological performance of Salicornia ramosissima J. Woods under optimal and sub-optimal saline conditions

Increasing extreme temperature climatic events could exert an important effect on plant photosynthetic performance, which could be modulated by the co-occurrence with other environmental factors, such as salinity, in estuarine ecosystems. Therefore, a mesocosm experiment was designed to assess the impact of temperature events for three days (13/5 °C, 25/13 °C and 40/28 °C) in combination with two NaCl concentrations (171 and 1050 mM NaCl) on the physiological performance of Salicornia ramosissima. Extreme temperature events had a negative impact on S. ramosissima photosynthetic efficiency, this effect being more marked with cold wave at both salinities, compared with heat wave, even in presence of NaCl excess. This differential thermotolerance in the photosynthetic apparatus was ascribed to the greater integrity and functioning of its photosynthetic pathway at high temperature, as indicated by constant gs, Vc,max values at optimal salinity and the higher values of those parameters and gm recorded in combination with NaCl excess. Moreover, S. ramosissima was able to upregulate the energy sink capacity of its photochemical apparatus at elevated temperature and salinity by a greater energy excess dissipation capacity. This could have contributed to reducing the risk of oxidative stress, along with the recorded higher capacity for antioxidant enzyme activity modulation under these conditions.

Phytoplankton community-level bio-optical assessment in a naturally mercury contaminated Antarctic ecosystem (Deception Island)

Mercury naturally contaminated environments, like Deception Island (Antarctica), are field labs to study the physiological consequences of chronic Hg-exposure at the community level. Deception Island volcanic vents lead to a continuous chronic exposure of the phytoplanktonic communities to potentially toxic Hg concentrations. Comparing Hg-contaminated areas (Fumarolas Bay - FB, Gabriel de Castilla station - GdC station), no significant differences in chlorophyll a concentrations were detected, indicating that biomass production was not impaired by Hg-exposure despite the high Hg levels found in the cells. Moreover, the electron transport energy, responsible for energy production, also presented rather similar values in phytoplankton from both locations. Regarding FB communities, although the cells absorbed and trapped lower amounts of energy, the effect of Hg was not relevant in the photochemical work produced by the electronic transport chain. This might be due to the activation of alternative internal electron donors, as counteractive measure to the energy accumulated inside the cells. In fact, this alternative electron pathway, may have allowed FB communities to have similar electron transport energy fluxes without using respiration as photoprotective measure towards excessive energy. Hg-exposed cells also showed a shift from the energy flux towards the PS I (photosystem I), alleviating the excessive energy accumulation at the PS II (photosystem II) and preventing an oxidative burst. Our findings suggest a higher energy use efficiency in the communities exposed to volcanic Hg, which is not observable in cultured phytoplankton species grown under Hg exposure. This may constitute a metabolic adaptation, driven from chronic exposure allowing the maintenance of high levels of primary productivity under the assumingly unfavourable conditions of Deception Island.

Induction of apoptosis and G1 phase cell cycle arrest by Aster incisus in AGS gastric adenocarcinoma cells

In recent decades, various bioactive compounds from plants have been investigated for their potential use in the treatment of diseases in humans. Aster incisus extract (AIE) is the extract of a common plant that is mostly found in Asia. It has traditionally been used for medicinal purposes in South Korea. In this study, we evaluated the potential anticancer effects of a methanolic extract of Aster incisus in a normal human cell line (HaCaT keratinocytes) and in 4 different types of human cancer cell lines (A549, lung cancer; Hep3B, liver cancer; MDA‑MB‑231, breast cancer; and AGS, gastric cancer). The HaCaT, A549, Hep3B, MDA‑MB‑231 and AGS cells were treated with various concentrations of AIE and following treatment, cell survival was evaluated. Additional analyses, such as WST-1 assay, western blot analysis, DAPI staining, flow cytometry, immunofluorescence staining and wound healing assay were performed to elucidate the mechanisms and pathways involved in the cell death induced by AIE. Treatment with AIE induced morphological changes and considerably reduced the viability of the both normal and cancer cell lines. Further analysis of the AGS gastric cancer cells revealed that AIE led to the induction of apoptosis and a high accumulation of cells in the G1 cell phase following treatment with AIE in a dose-dependent manner. The results also revealed that AIE successfully suppressed the migration of the AIE-treated AGS cells. The results of western blot analysis indicated that AIE increased the expression of pro-apoptotic proteins, particularly Bid, Bad, Bak, cytochrome c, apoptosis inducing factor (AIF), cleaved caspase‑3, -8 and -9 and cleaved poly(ADP-ribose) polymerase (PARP). Additionally, AIE decreased the expression of the anti-apoptotic proteins, Bcl-2 and Bcl-xL. On the whole, the findings of this study demonstrate that AIE induces apoptosis through the activation of the caspase‑dependent pathway mediated by the mitochondrial pathway and by arresting the cell cycle in AGS cells.

Disentangling the effect of atmospheric CO2 enrichment on the halophyte Salicornia ramosissima J. Woods physiological performance under optimal and suboptimal saline conditions

A mesocosm experiment was designed to assess the effect of atmospheric CO₂ increment on the salinity tolerance of the C₃ halophyte Salicornia ramosissima. Thus, the combined effect of 400 ppm and 700 ppm CO₂ at 0, 171 and 510 mM NaCl on plants growth, gas exchange, chlorophyll fluorescence parameters, pigments profiles, antioxidative enzyme activities and water relations was studied. Our results highlighted a positive effect of atmospheric CO₂ increment on plant physiological performance under suboptimal salinity concentration (510 mM NaCl). Thus, we recorded higher net photosynthetic rate (A_N) values under saline conditions and 700 ppm CO₂, being this effect mainly mediated by a reduction of mesophyll (g_m) and biochemical limitation imposed to salt excess. In addition, rising atmospheric CO₂ led to a better plant water balance, linked with a reduction of stomatal conductante (g_s) and an overall increment of osmotic potential (Ѱ_o) with NaCl concentration increment. In spite of these positive effects, there were no significant biomass variations between any treatments. Being this fact ascribed by the investment of the higher energy fixed for salinity stress defence mechanisms, which allowed plants to maintain more active the photochemical machinery even at high salinities, reducing the risk of ROS production, as indicated an improvement of the electron flux and a rise of the energy dissipation. Finally, the positive effect of the CO₂ was also supported by the modulation of pigments profiles (mainly zeaxhantin and violaxhantin) concentrations and anti-oxidative stress enzymes, such as superoxide dismutase (SOD) and ascorbate peroxidase (APx).

Ectomycorrhizal inoculation with Pisolithus tinctorius reduces stress induced by drought in cork oak

We investigated whether the performance of cork oak under drought could be improved by colonization with the ectomycorrhizal fungus Pisolithus tinctorius. Results show that inoculation alone had a positive effect on plant height, shoot biomass, shoot basal diameter, and root growth. Under drought, root growth of mycorrhizal plants was significantly increased showing that inoculation was effective in increasing tolerance to drought. In accordance, mycorrhizal plants subjected to drought showed less symptoms of stress when compared to non-mycorrhizal plants, such as lower concentration of soluble sugars and starch, increased ability to maintain fatty acid content and composition, and increased unsaturation level of membrane lipids. After testing some of the mechanisms suggested to contribute to the enhanced tolerance of mycorrhizal plants to drought, we could not find any by which Pisolithus tinctorius could benefit cork oak, at least under the drought conditions imposed in our experiment. Inoculation did not increase photosynthesis under drought, suggesting no effect in sustaining stomatal opening at low soil water content. Similarly, plant water status was not affected by inoculation suggesting that P. tinctorius does not contribute to an increased plant water uptake during drought. Inoculation did increase nitrogen concentration in plants but it was independent of the water status. Furthermore, no significant mycorrhizal effect on drought-induced ROS production or osmotic adjustment was detected, suggesting that these factors are not important for the improved drought tolerance triggered by P. tinctorius.

Leaf fatty acid remodeling in the salt-excreting halophytic grass Spartina patens along a salinity gradient

Spartina patens is a highly dispersed halophytic grass invader in Mediterranean marshes. It is also characterized by having a high degree of resistance to salinity, one of the main drivers of plant zonation in salt marshes. Nevertheless, the physiological basis behind the extreme resistance of S. patens requires more detailed studies. In the present work, we aimed to study how membrane fatty acid remodeling could contribute to the resistance of this plant to salt. Spartina patens individuals exposed to increasing levels of salinity and its leaf fatty acid profile under lipid peroxidation products evaluated under all tested concentrations. A significant increase in the relative amounts of the saturated fatty acids (SFA) was observed, namely palmitic acid (C16:0), essential for PS II functioning, and stearic (C18:0) acid. The chloroplastidial trans-hexadecenoic acid (C16:1t) as well as the polyunsaturated linoleic (C18:2) and linolenic (C18:3) acids showed significant decreases in all the salt treatments. These changes led to a reduction in the double bond index in salt-treated plants which reflects reduction of the fluidity of the chloroplast membranes, which could contribute to maintain the membrane impermeable to the toxic exogenous Na. Despite the decrease observed in the total fatty acid contents in plants exposed to high salt concentrations the amounts of lipid peroxidation products decreased highlighting the resistance of this species towards toxic exogenous salt concentrations. Membrane fatty acid remodeling could represent an efficient mechanism to maintain the photosynthetic machinery of S. patens highly efficient under salt stress.