Long-term Environmental Stress Research Articles

N-glycosylation of SnRK2s affects NADPH maintenance in peroxisomes during prolonged ABA signalling

Unfavourable conditions, such as prolonged drought and high salinity, pose a threat to the survival and agricultural yield of plants. The phytohormone ABA plays a key role in the regulation of plant stress adaptation and is often maintained at high levels for extended periods. While much is known about ABA signal perception and activation in the early signalling stage, the molecular mechanism underlying desensitization of ABA signalling remains largely unknown. Here we demonstrate that in the endoplasmic reticulum (ER)-Golgi network, the key regulators of ABA signalling, SnRK2.2/2.3, undergo N-glycosylation, which promotes their redistribution from the nucleus to the peroxisomes in Arabidopsis roots and influences the transcriptional response in the nucleus during prolonged ABA signalling. On the peroxisomal membrane, SnRK2s can interact with glucose-6-phosphate (G6P)/phosphate translocator 1 (GPT1) to maintain NADPH homeostasis through increased activity of the peroxisomal oxidative pentose phosphate pathway (OPPP). The resulting maintenance of NADPH is essential for the modulation of hydrogen peroxide (H2O2) accumulation, thereby relieving ABA-induced root growth inhibition. The subcellular dynamics of SnRK2s, mediated by N-glycosylation suggest that ABA responses transition from transcriptional regulation in the nucleus to metabolic processes in the peroxisomes, aiding plants in adapting to long-term environmental stress.

Genetic benefits of female from extra-pair paternity are context dependent within the socially monogamous Tree Sparrow

Females actively seek extra-pair paternity (EPP) to acquire a fitness advantage for their offspring. The “context-dependence hypothesis” posits that female extra-pair mate choice has plasticity in response to environmental conditions, and therefore magnitude of female genetic benefits from EPP depends on the environmental variation. Furthermore, chronic heavy metal pollution can cause adverse effects on fitness-related traits of wild birds. However, few studies were available on the interactions between heavy metal pollution and EPP. We selected an area that was contaminated by heavy metals for more than 60 years (Baiyin, BY), a relatively unpolluted area (Liujiaxia, LJX), and Tree Sparrows (Passer montanus) as study species to explore the response of female extra-pair mate choice and genetic benefits from EPP to heavy metal pollution in socially monogamous birds. The relatedness between social mates and extra-pair mates was investigated. Additionally, we compared the body size and heterozygosity of extra-pair offspring (EPO), within-pair offspring (WPO), social males and extra-pair males from the two Tree Sparrow populations. We found that at BY, female Tree Sparrows tended to choose extra-pair males with larger body size and lower genetic similarity, thereby producing higher heterozygosity and larger body size of EPO compared with those of WPO. However, no similar phenomenon was observed in the Tree Sparrow population from LJX. In addition, there was a significant interaction between population and paternity in the analyses of the fitness-related traits, suggesting that environmental variation could affect female genetic benefits from EPP. This study confirmed the existence of presumed interactions between environmental pollution and EPP within the natural population of socially monogamous Tree Sparrows. Our findings shed lights on the possible effects of long-term environmental stress on mating system in wild birds.

Participants in the Trans-Antarctic Winter Traverse Expedition Showed Increased Bacterial Load and Diversity in Saliva but Maintained Individual Differences within Stool Microbiota and Across Metabolite Fingerprints.

Understanding the impact of long-term physiological and environmental stress on the human microbiota and metabolome may be important for the success of space flight. This work is logistically difficult and has a limited number of available participants. Terrestrial analogies present important opportunities to understand changes in the microbiota and metabolome and how this may impact participant health and fitness. Here, we present work from one such analogy: the Transarctic Winter Traverse expedition, which we believe is the first assessment of the microbiota and metabolome from different bodily locations during prolonged environmental and physiological stress. Bacterial load and diversity were significantly higher during the expedition when compared with baseline levels (p < 0.001) in saliva but not stool, and only a single operational taxonomic unit assigned to the Ruminococcaceae family shows significantly altered levels in stool (p < 0.001). Metabolite fingerprints show the maintenance of individual differences across saliva, stool, and plasma samples when analysed using flow infusion electrospray mass spectrometry and Fourier transform infrared spectroscopy. Significant activity-associated changes in terms of both bacterial diversity and load are seen in saliva but not in stool, and participant differences in metabolite fingerprints persist across all three sample types.

Aquatic quillworts, Isoëtes echinospora and I. lacustris under acidic stress-A review from a temperate refuge.

Quillworts (Isoëtes) represent highly specialized flora of softwater lakes, that is, freshwater ecosystems potentially sensitive to acidification. In this paper, we combine a review of previous studies and our new results to address unrecognized reproduction strategies of quillworts to overcome long-term environmental stresses. These strategies play an important role in the plant's ability to overcome atmospheric acidification of freshwaters, protecting the plants until their environment can recover. Environmental drivers of recovery of Isoëtes echinospora and I. lacustris were studied in two acidified lakes in the Bohemian Forest (Central Europe). Both populations survived more than 50 years of severe acidification, although they failed to recruit new sporelings. Their survival depended entirely on the resistance of long-living adult plants because the quillworts do not grow clonally. During the past two decades, a renewal of I. echinospora population inhabiting Plešné Lake has been observed, while no such renewal of I. lacustris, dwelling in Černé Lake, was evident, despite similar changes in water composition occurring in both lakes undergoing advanced recovery from acidification. Our in vitro experiments revealed that the threshold acidity and toxic aluminium concentrations for sporeling survival and recruitment success differed between I. echinospora (pH ≤ 4.0 and ≥300 μg L-1 Al at pH5) and I. lacustris (pH ≤ 5.0 and ≥100 μg L-1Al at pH5). The higher sensitivity of I. lacustris to both stressors likely stems from its year-long germination period and underlines the risk of exposure to chronic or episodic acidification in recovering lakes. By contrast, the shorter germination period of I. echinospora (2-3months) enables its faster and deeper rooting, protecting this quillwort from periodic acidification during the next snowmelt. Our study brings novel insights into widely discussed environmental issues related to the long-term degradation of softwater lakes, which represent important hotspots of pan-European biodiversity and conservation efforts.

Rumen-protected zinc-methionine dietary inclusion alters dairy cow performances, and oxidative and inflammatory status under long-term environmental heat stress.

Dairy cows are susceptible to heat stress due to the levels of milk production and feed intake. Dietary supplemental amino acids, particularly rate-limiting amino acids, for example, methionine (Met), may alleviate the potential negative consequences. Zinc (Zn) is beneficial to the immune system and mammary gland development during heat stress. We investigated the impact of a source of a rumen-protected Zn-Met complex (Loprotin, Kaesler Nutrition GmbH, Cuxhaven, Germany) in high-producing Holstein cows during a long-term environmental heat stress period. A total of 62 multiparous lactating Holstein cows were allocated in a completely randomized design to two dietary treatments, namely, basal diet without (control) and basal diet with the supplemental Zn-Met complex (RPZM) at 0.131% of diet DM. Cows in the RPZM group had higher energy-corrected milk (46.71 vs. 52.85 ± 1.72 kg/d for control and RPZM groups, respectively) as well as milk fat and protein concentration (27.28 vs. 32.80 ± 1.82 and 30.13 vs. 31.03 ± 0.25 g/kg for control and RPZM groups, respectively). The Zn-Met complex supplemented cows had lower haptoglobin and IL-1B concentration than the control (267 vs. 240 ± 10.53 mcg/mL and 76.8 vs. 60.0 ± 3.4 ng/L for control and RPZM groups, respectively). RPZM supplementation resulted in better oxidative status, indicated by higher total antioxidant status and lower malondialdehyde concentrations (0.62 vs. 0.68 ± 0.02 mmol/L and 2.01 vs. 1.76 ± 0.15 nmol/L for control and RPZM groups, respectively). Overall, the results from this study showed that RPZM dietary inclusion could maintain milk production and milk composition of animals during periods of heat stress. Enhanced performance of animals upon Zn-Met complex supplementation could be partly due to improved oxidative and immune status.

Standing stock and composition of macrozoobenthos in the south-eastern Arabian Sea: A revisit after a decade

Changes in macrozoobenthic standing stock and composition along the south-eastern Arabian Sea continental shelf (30–200 m) are investigated, based on data collected from the same sites during the same season 14 years apart (winter monsoon, 1998 and 2012), using the same platform, sampling gear, methods etc. During both surveys, polychaetes dominated among the macrozoobenthos, followed by crustaceans and molluscs. A decline in macrozoobenthic density and biomass with increasing depth was noted in both surveys. Macrozoobenthic density increased significantly between 1998 and 2012, especially in the inner and mid shelf (30–50 m), due to the increase in density of polychaetes and molluscs, while the density of crustaceans decreased. The mean individual body weight of polychaetes decreased between 1998 and 2012, most notably in the inner and mid shelf (30–50 m). This reflected an overall increased dominance of small-sized opportunists such as spionids, magelonids, paraonids, cirratulids and pilargids in 2012 across the entire shelf. Such an increase in dominance of opportunists and decline in abundance of sensitive taxa is indicative of long-term environmental stress and anthropogenic pressure. However, no significant changes were noted in the measured environmental variables which are known to influence benthic faunal distribution in the region, such as sediment nature and oxygen availability. The observed changes may rather be indicative of the long-term effect of intense bottom trawling, which is practiced in the study area year-round. This is the first study of its kind for soft-sediment shelf benthos from the tropical belt.

Understanding the hazards induced by microplastics in different environmental conditions

Microplastics that are chemically and physically changed by exposure to environmental stress are emerging as a potential hazard to human health. Research on plastics exposed to long-term environmental stress is fundamentally needed. In this study, four plastics (acrylonitrile butadiene styrene [ABS], polyvinyl chloride [PVC], polystyrene [PS], and polyethylene [PE]) were selected to describe nature-derived microplastics and to analyze their chemical/physical changes, which are potential hazards to the human health, by environmental stress. To mimic the microplastic exposed to long-term environmental stress, we used accelerated aging, lab-scale aging in the environmental conditions((1) UV (2) enzyme (3) seawater). To quantify the percentage of the microplastic size changes, the image patterns of the generated microplastics were converted into numerical values using image-j. The size of the microplastics was reduced by at least 32% in (3) seawater environmental conditions. PE was reduced by at least 46% compared to the size of the bare sample in the environmental conditions. Significantly, the size of the PE has decreased by more than 87% in (3) seawater environmental conditions; also, chemical composition change (−O−CO−/−OH group formation) but not crystallinity changes through infrared and thermal analysis. Therefore, our results suggest that microplastic (PE) exposed to the ocean induces the potential hazards to affect human health.

Antioxidants, lysosomes and elements status during the life cycle of sea trout Salmo trutta m. trutta L.

The aim of our study was to elucidate the effects of both development stages (parr, smolt, adult, spawner), and kelt as a survival form and sex (male, female) on the functional stability of the lysosomal complex, biomarkers of oxidative stress, and element contents in the muscle tissue of the sea trout (Salmo trutta m. trutta L.) sampled in the Pomerania region (northern Poland). We have evaluated the maximal activities of lysosomal enzymes (alanyl aminopeptidase, leucyl aminopeptidase, β-N-acetylglucosaminidase, and acid phosphatase), lipid peroxidation level, and protein carbonyl derivatives as indices of muscle tissue degradation. The relationship between lysosomal activity and oxidative stress biomarkers estimated by the lipid peroxidation level and protein carbonyl derivatives was also assessed, as well as the relationships between element levels and oxidative stress biomarkers. Trends of the main effects (i.e., the development stages and sex alone, the interaction of the sex and development stage simultaneously) on oxidative stress biomarkers, lysosomal functioning, and element contents in the muscle tissue were evaluated. The study has shown sex-related relationships between the pro- and antioxidant balance and the tissue type in the adult stage as well as modifications in the lysosomal functioning induced by long-term environmental stress associated with changing the habitats from freshwater to seawater and intense migrations. The highest level of toxic products generated in oxidative reactions and oxidative modification of proteins was noted in both the spawner stage and the kelt form. The holistic model of analysis of all parameters of antioxidant defense in all development stages and sex demonstrated the following dependencies for the level of lipid peroxidation, oxidative modification of proteins, lysosomal activities, and element contents: TBARS > OMP KD > OMP AD > TAC, AcP > NAG > LAP > AAP and Cu > Fe > Ca > Mn > Zn > Mg, respectively.

Comparative analysis of drought-responsive and -adaptive genes in Chinese wingnut (Pterocarya stenoptera C. DC)

BackgroundDrought is the main stress factor for the cultivation of Pterocarya stenoptera in urban areas, and this factor will cause its dehydration and affect its growth. Identifying drought-related genes will be useful for understanding the drought adaptation mechanism of P. stenoptera.ResultsWe used physiological indicator detection, comparative transcriptome sequencing, and reanalysis on the results of previous landscape genomics studies to investigate the drought adaptation mechanism in P. stenoptera. The changes in malondialdehyde content showed that P. stenoptera was remarkably affected by drought stress, and the increase in soluble sugar content suggested its important role in response to drought stress. Results of comparative transcriptome sequencing showed that P. stenoptera initiated a series of programs, such as increasing the gene expression of unsaturated fatty acids, tyrosine, and plant pathogen resistance, to deal with the transient drought stress. According to the annotated results in a previous study, P. stenoptera adapts to the long-term differential drought stress by regulating the thickness of cell walls and expressing upper or lower limits of the downstream genes in the hormone signaling pathway. Through the comparative analysis of drought-responsive and -adaptive genes in P. stenoptera, this study supports the hypothesis that the environment-responsive genes (ERGs) introduced by the transient environmental stresses will be substantially more than the environment-adaptive genes (EAGs) in response to long-term differential environmental stresses, and the EAGs are not necessarily ERGs.ConclusionsOur study identified drought-responsive and -adaptive genes in P. stenoptera and revealed that P. stenoptera increased the gene expression of unsaturated fatty acids, tyrosine, and plant pathogen resistance in response to transient drought stress. This study reveals the different adaptation mechanism of P. stenoptera under the transient and long-term differential drought stresses.

The Role of Potassium Channels in Chronic Stress-Induced Brain Injury.

Chronic stress-induced brain injury (CSBI) is the organic damage of brain tissue caused by long-term psychological and environmental stress. However, there is no effective drug for the treatment of CSBI. The present study aimed to investigate possible mechanisms of CSBI and to explore related therapeutic targets. A rat model of CSBI was established by combining chronic restraint and cold water immersion. Our CSBI model was validated via Nissl staining, Western blotting, and behavioral tests. RNA sequencing (RNA-seq) was used to identify differentially expressed genes (DEGs) within brain tissue during CSBI. Both Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) analyses were performed to determine signaling pathways associated with CSBI-induced DEGs. Agonists/antagonists were used to validate the pharmacodynamics of potential therapeutic targets. A combination of chronic restraint and cold water immersion successfully induced a rat model of CSBI, as indicated by various markers of brain injury and cell apoptosis that were verified via Nissl staining, Western blotting, and behavioral tests. RNA-seq analysis identified 1131 DEGs in CSBI rats. Of these DEGs, 553 genes were up-regulated and 778 genes were down-regulated. GO and KEGG pathway analyses revealed that significant DEGs were predominantly related to membrane-bound ion channels, among which the potassium channel function was found to be significantly affected. Pharmacological experiments revealed that retigabine, a voltage-gated potassium channel opener, demonstrated a protective effect in CSBI rats. Taken together, our findings suggest that potassium channel function is disrupted in CSBI, and that potassium channel regulators may function as anti-CSBI drugs.

Coral bioerosion on the marginal reefs of northeastern Arabia

The maintenance of coral reef framework results from a balance between skeletal accretion and bioerosion, and this balance can be disrupted by environmental stress and disturbance. Coral reefs in northeastern Arabia exist in extreme environmental conditions and have experienced severe disturbances in recent years. This study assessed the intensity of macrobioerosion in two regionally common species, Platygyra daedalea and Cyphastrea microphthalma, at three sites within the southern Persian/Arabian Gulf and at one site in the Sea of Oman. On average, bioeroders removed 9.2 ± 1.6% of the skeletal surface area in P. daedalea and 26.4 ± 1.6% in C. microphthalma, with variation between species attributed to differences in colony morphology. Bioerosion intensity varied among sites in each species. Within the southern Arabian Gulf, both P. daedalea and C. microphthalma showed the highest bioerosion intensity at Delma, in the western region, compared with that of Saadiyat or Ras Ghanada to the east, with the elevated bioerosion at Delma consistent with a history of more extreme environmental conditions and bleaching-related disturbances. The highest bioerosion in P. daedalea occurred at Fujairah in the Sea of Oman, and this site was amongst the highest in C. microphthalma. Although this site is characterized by more benign environmental conditions, reefs in this area experienced mass coral mortality due to anoxia during a large-scale harmful algal bloom in 2008/9 and the high bioerosion in Fujairah likely represents a long-term signature of this disturbance. The intensity of macrobioerosion observed here is high compared with other regions, suggesting that that chronic exposure to long-term environmental stress and a history of disturbance may lead enhanced loss of reef framework.

The flight response impairs cytoprotective mechanisms by activating the insulin pathway.

An animal’s stress response requires different adaptive strategies depending on the nature and duration of the stressor. While acute stressors, like predation, induce a rapid and energy-demanding fight or flight response, long-term environmental stressors induce the gradual and long-lasting activation of highly conserved cytoprotective processes1–3. In animals across the evolutionary spectrum the continued activation of the fight-or-flight response weakens the animal’s resistance to environmental challenges4,5. However, the molecular and cellular mechanisms that regulate the trade-off between flight response and long-term stressors are poorly understood. Here we show that repeated induction of the C. elegans flight response shortens lifespan and inhibits conserved cytoprotective mechanisms. The flight response activates neurons that release tyramine, the invertebrate analog of adrenaline/noradrenaline. Tyramine stimulates the DAF-2/Insulin/IGF-1 pathway and precludes the induction of stress response genes by activating an adrenergic-like receptor in the intestine. In contrast, long-term environmental stressors, such as heat or oxidative stress, reduce tyramine release allowing the induction of cytoprotective genes. These findings demonstrate that a neural stress-hormone supplies a state-dependent neural switch between acute flight and long-term environmental stress responses and provides mechanistic insights into how the flight response impairs cellular defense systems and accelerates aging.

Uppermost Permian trace fossils along a shelf to slope transect in South China and their implications for oceanic redox evolution and extinction pattern

Abstract Trace fossils are important evidence of benthic activity and proxies of bottom and interstitial water oxygen content, making them a promising tool to understand the oceanic redox evolution and extinction patterns during the end-Permian mass extinction (EPME). Detailed bed-by-bed ichnologic studies were performed at a high-resolution scale from two uppermost Permian sections (Shangsi and Dongpan) in South China, documenting the presence of Chondrites targionii, Chondrites isp., Nereites isp., Planolites isp. A, Planolites isp. B, Palaeophycus isp., Phycosiphon incertum, Thalassinoides isp., and Zoophycos isp. The uppermost Permian strata at the Shangsi section mainly comprise siliceous limestone interbedded with illite-montmorillonite claystone and shale, recording a deep shelf setting. The uppermost Permian strata at the Dongpan section consist of mixed chert, mudstone and claystone, formed in a slope environment. Bioturbation index in uppermost Permian strata is mostly 1–2, but with thin intervals reaching 3–4. Fluctuating bioturbation intensities, ichnofaunal composition (Thalassinoides, Planolites, Zoophycos) and ethologies, as well as the ratio of highly reactive iron to total iron (FeHr/FeT) and the proportion of the highly reactive iron pool in the form of pyrite (Fepy/FeHR) suggest that bottom and interstitial oxygen levels were not permanently anoxic/euxinic, but were interrupted by brief periods of aerobic conditions during the latest Permian. Three bioturbation phases in the EPME are identified. Phase I is characterized by the absence of typical pascichnia ichnotaxa (e.g. Nereites isp.) and relatively large fodinichnia burrow (e.g., Planolites isp. B; Zoophycos isp.). Phase II mainly consists of smaller Planolites isp. A, Thalassinoides isp. and Chondrites isp., recording a transition from softground to firmground. Only occasional smaller Planolites isp. A occur in Phase III without any associated vertical burrows. Ichnodiversity and bioturbation index from Phase I to Phase III show a step by step decline, corresponding to the two-stage extinction patterns. Long-term environmental stress (e.g., oceanic anoxia, volcanic winter, global warming, ocean acidification, hypercapnia) may have played major role in the collapse of the infaunal ecospace and only facies-crossing, highly tolerant, opportunistic organisms may have persisted in otherwise vacant ecological niches in the aftermath of the extinction.

Expression of homing endonuclease gene and insertion-like element in sea anemone mitochondrial genomes: Lesson learned from Anemonia viridis

The mitochondrial genomes of sea anemones are dynamic in structure. Invasion by genetic elements, such as self-catalytic group I introns or insertion-like sequences, contribute to sea anemone mitochondrial genome expansion and complexity. By using next generation sequencing we investigated the complete mtDNAs and corresponding transcriptomes of the temperate sea anemone Anemonia viridis and its closer tropical relative Anemonia majano. Two versions of fused homing endonuclease gene (HEG) organization were observed among the Actiniidae sea anemones; in-frame gene fusion and pseudo-gene fusion. We provided support for the pseudo-gene fusion organization in Anemonia species, resulting in a repressed HEG from the COI-884 group I intron. orfA, a putative protein-coding gene with insertion-like features, was present in both Anemonia species. Interestingly, orfA and COI expression were significantly up-regulated upon long-term environmental stress corresponding to low seawater pH conditions. This study provides new insights to the dynamics of sea anemone mitochondrial genome structure and function.

Transcriptomic responses to environmental change in fishes: Insights from RNA sequencing

The need to better understand how plasticity and evolution affect organismal responses to environmental variability is paramount in the face of global climate change. The potential for using RNA sequencing (RNA-seq) to study complex responses by non-model organisms to the environment is evident in a rapidly growing body of literature. This is particularly true of fishes for which research has been motivated by their ecological importance, socioeconomic value, and increased use as model species for medical and genetic research. Here, we review studies that have used RNA-seq to study transcriptomic responses to continuous abiotic variables to which fishes have likely evolved a response and that are predicted to be affected by climate change (e.g., salinity, temperature, dissolved oxygen concentration, and pH). Field and laboratory experiments demonstrate the potential for individuals to respond plastically to short- and long-term environmental stress and reveal molecular mechanisms underlying developmental and transgenerational plasticity, as well as adaptation to different environmental regimes. We discuss experimental, analytical, and conceptual issues that have arisen from this work and suggest avenues for future study.

Fluctuating asymmetry rather than oxidative stress in Bufo raddei can be an accurate indicator of environmental pollution induced by heavy metals.

Oxidative stress (OS) and fluctuating asymmetry (FA) as risk markers for environmental stress are widely used to predict changes in the health and fitness of many animals exposed to pollutants. However, from the perspective of protecting declining amphibians, it remains to be verified which one would be a reliable indicator for amphibians exposed to long-term heavy metal pollution under natural conditions. In this study, the OS and FA of Bufo raddei exposed to natural heavy metal pollution were analyzed to determine which marker is more accurate for indicating heavy metal-induced stress. Three years of data were collected during the breeding season of B. raddei from Baiyin (BY), which has been mainly contaminated with Cu, Zn, Pb, and Cd compounds for a long period, and from Liujiaxia (LJX), which is a relatively unpolluted area. Unexpectedly, although significant accumulation of the four heavy metals was found in the kidney and liver of B. raddei from BY, the levels of superoxide dismutase, glutathione peroxidase, and malondialdehyde in these two organs were found to be irregular, with low repeatability in both BY and LJX. However, significant differences in the levels of FA were observed in B. raddei populations from these two areas over the past 3years (P<0.01). The degrees of FA in B. raddei populations from BY and LJX were assessed as degree 4 and 1, respectively. In short, this study suggested that FA was a more reliable and effective indicator than OS to monitor and predict long-term environmental stress on anuran amphibians.

The Stenohaline Seagrass Posidonia oceanica Can Persist in Natural Environments Under Fluctuating Hypersaline Conditions

The Mediterranean endemic seagrass Posidonia oceanica is generally regarded as a stenohaline species, highly sensitive to salinity increments; however, in a few particular cases, natural populations can grow under salinity levels above its normal threshold of tolerance. One such case is a population of P. oceanica in the southeastern coastal region of Spain, which is able to survive under the fluctuating influence of hypersaline waters coming from an adjacent coastal lagoon (Mar Menor). The present work examines the physiological mechanisms underlying the species’ ability to overcome this hypersaline stress and persist in the long term. To this end, the physiological, morphological, and population statuses of plants from the site of influence were compared to those from a reference site where plants grew under normal conditions. P. oceanica leaves from the influenced sites showed more negative water potentials than those from the reference sites as a response to maintain a positive water balance under hypersaline conditions. However, these lower water potentials were not explained by the accumulation of intracellular solutes since their osmotic potential were similar to reference leaves and their ionic content generally lower. In addition, these leaves also accumulated higher concentrations of proline and soluble sugars but these organic osmolytes are more likely acting as osmo-protectants, rather than as osmoticums. These responses indicated that plants growing at the influenced site have developed physiological strategies to maintain lower ion concentration in their leaf tissues in order to avoid the alteration of ion homeostasis (i.e., ionic ratios), which can be toxic for plant metabolism. Photosynthesis and photochemistry were not adversely affected in leaves exposed to hypersalinity; in fact, these processes showed a tendency to become enhanced, possibly to support the assimilation of anthropogenic nitrogen coming from the lagoon waters. At the individual and population levels, P. oceanica plants growing under the influence of hypersaline waters exhibited a marked reduction in shoot size compared to those at the reference site, while shoot density and population growth rates were similar to those of the reference site and remained stable over time. This shoot size reduction involves a lower demand of metabolic resources necessary to maintain vegetative structures, which is mainly required for metabolic adjustments at the physiological level. We propose that this morphological adaptation serves as a stress-coping mechanism, helping the species to inhabit this unfavorable environment, as has been widely described for terrestrial plants subjected to long-term environmental stress.

Light quality and quantity regulate aerobic methane emissions from plants.

Studies have been mounting in support of the finding that plants release aerobic methane (CH4 ), and that these emissions are increased by both short-term and long-term environmental stress. It remains unknown whether or not they are affected by variation in light quantity and quality, whether emissions change over time, and whether they are influenced by physiological parameters. Light is the primary energy source of plants, and therefore an important regulator of plant growth and development. Both shade-intolerant sunflower and shade-tolerant chrysanthemum were investigated for the release of aerobic CH4 emissions, using either low or high light intensity, and varying light quality, including control, low or normal red:far-red ratio (R:FR), and low or high levels of blue, to discern the relationship between light and CH4 emissions. It was found that low levels of light act as an environmental stress, facilitating CH4 release from both species. R:FR and blue lights increased emissions under low light, but the results varied with species, providing evidence that both light quantity and quality regulate CH4 emissions. Emission rates of 6.79-41.13 ng g-1 DW h-1 and 18.53-180.25 ng g-1 DW h-1 were observed for sunflower and chrysanthemum, respectively. Moreover, emissions decreased with age as plants acclimated to environmental conditions. Since effects were similar in both species, there may be a common trend among a number of shade-tolerant and shade-intolerant species. Light quantity and quality are influenced by factors including cloud covering, so it is important to know how plants will be affected in the context of aerobic CH4 emissions.

Effects of Escitalopram on a Rat Model of Persistent Stress-Altered Hedonic Activities: Towards a New Understanding of Stress and Depression.

Chronic mild stress (CMS) paradigm is a model to simulate clinical depression induced by long-term environmental stress. The present study investigated the effects of escitalopram, a specific serotonin reuptake inhibitor (SSRI), on depression-like activities in adult (18 week-old) Sprague-Dawley (SD) rats that underwent a total 8-week CMS. Body weight, locomotor activity and sucrose consumption of the rats were measured under CMS paradigm and following escitalopram treatment. The plasma level of corticosterone was also measured at the end of the experiment. Our results revealed that the CMS program reduced the body weight, but not the locomotor activity of the rats. Adult SD rats consumed less sucrose solution under CMS. However, chronic escitalopram regime (10 mg/kg/day for 4 weeks) appeared not helpful in reversing this CMS effect and, if any, the drug exaggerated anxiety profile of the animals. Unexpectedly, the stressed rats exhibited higher sucrose consumption than non-stressed rats after receiving repeated saline injections. Further, the stressed rats were found to have a higher plasma level of corticosterone after escitalopram treatment. Our results provide an example of the possibility that previously stressed individuals may develop an anti-depression ability that lessens the benefits of intervention with antidepressants. Finally, a separate group of rats that entered the CMS program at 10 week-old were used to examine possible effects of aging to interpret the stress coping ability observed in the 18 week-old rats. The younger rats developed less anti-anhedonia effects under repeated saline injections. The data of the present study provide a different perspective on stress-induced depression and possible interaction with antidepressants.

Multivariate and phylogenetic analyses assessing the response of bacterial mat communities from an ancient oligotrophic aquatic ecosystem to different scenarios of long-term environmental disturbance.

Understanding the response of bacterial communities to environmental change is extremely important in predicting the effect of biogeochemical modifications in ecosystem functioning. The Cuatro Cienegas Basin is an ancient oasis in the Mexican Chihuahuan desert that hosts a wide diversity of microbial mats and stromatolites that have survived in extremely oligotrophic pools with nearly constant conditions. However, thus far, the response of these unique microbial communities to long-term environmental disturbances remains unexplored. We therefore studied the compositional stability of these bacterial mat communities by using a replicated (3x) mesocosm experiment: a) Control; b) Fluct: fluctuating temperature; c) 40C: increase to 40 ºC; d) UVplus: artificial increase in UV radiation; and f) UVmin: UV radiation protection. In order to observe the changes in biodiversity, we obtained 16S rRNA gene clone libraries from microbial mats at the end of the experiment (eight months) and analyzed them using multivariate and phylogenetic tools. Sequences were assigned to 13 major lineages, among which Cyanobacteria (38.8%) and Alphaproteobacteria (25.5%) were the most abundant. The less extreme treatments (Control and UVmin) had a more similar composition and distribution of the phylogenetic groups with the natural pools than the most extreme treatments (Fluct, 40C, and UVplus), which showed drastic changes in the community composition and structure, indicating a different community response to each environmental disturbance. An increase in bacterial diversity was found in the UVmin treatment, suggesting that protected environments promote the establishment of complex bacterial communities, while stressful environments reduce diversity and increase the dominance of a few Cyanobacterial OTUs (mainly Leptolyngbya sp) through environmental filtering. Mesocosm experiments using complex bacterial communities, along with multivariate and phylogenetic analyses of molecular data, can assist in addressing questions about bacterial responses to long-term environmental stress.