Identification of suitable reference genes for quantitative gene expression analysis in clam Cyclina sinensis under salinity stress and Vibrio infection

The appropriate reference gene is a prerequisite for accurate normalization of gene expression level,and research on suitable reference genes in clam Cyclina sinensis is scarce.To improve the situation,we selected five commonly used housekeeping genes,including β-actin,Elongation factor 1-α(EF1-α),Glyceraldehyde-3-pho sphate dehydrogenase(GAPDH),40S ribosomal protein S18(RPS18),and Tubulin a(TUB-α),then evaluated their expression stability in different adult tissues and under different experimental treatments(salinity stress and Vibrio parahaemolyticus infection).Their expression stability was analyzed by three frequently used programs,geNorm,NormFinder,and BestKeeper.This analysis indicated that multiple genes should be used for normalization,and we concluded that the reference gene combination GAPDH-RPS18-β-actin,should be used for qRT-PCR analysis in different tissues of C.sinensis under normal physiological conditions.For the clams under salinity stress and Vibrio infection,EF1-α-GAPDHRPS18 was recommended as the gene combination for qRT-PCR normalization.TUB-αwas generally poorly ranked by all programs,and should not be used in future studies.This study should provide fundamental support for accurate quantitative gene expression analysis of this species.

The soybean GmPUB21-interacting protein GmDi19-5 responds to drought and salinity stresses via an ABA-dependent pathway

Drought-induced protein 19(Di19) is a Cys2/His2 zinc-finger protein that functions in plant growth and development and in tolerance to abiotic stresses.Gm PUB21,an E3 ubiquitin ligase,negatively regulates drought and salinity response in soybean.We identified potential interaction target proteins of Gm PUB21by yeast two-hybrid c DNA library screening,Gm Di19-5 as a candidate.Bimolecular fluorescence complementation and glutathionine-S-transferase pull-down assays confirmed the interaction between Gm Di19-5 and Gm PUB21.Gm Di19-5 was induced by Na Cl,drought,and abscisic acid(ABA) treatments.Gm Di19-5 was expressed in the cytoplasm and nucleus.Gm Di19-5 overexpression conferred hypersensitivity to drought and high salinity,whereas Gm Di19-5 silencing increased drought and salinity tolerance.Transcripts of ABA-and stress response-associated genes including Gm RAB18 and Gm DREB2A were downregulated in Gm Di19-5-overexpressing plants under drought and salinity stresses.ABA decreased the protein level of Gm Di19-5 in vivo,whereas Gm PUB21 increased the decrease of Gm Di19-5 after exogenous ABA application.The accumulation of Gm PUB21 was also inhibited by Gm Di19-5.We conclude that Gm PUB21 and Gm Di19-5 collaborate to regulate drought and salinity tolerance via an ABA-dependent pathway.

Long Term Salinity Stress Reveals Variety Specific Differences in Root Oxidative Stress Response

Salinity stress induces oxidative stress caused by reactive oxygen species （ROS）： superoxide radicals, hydrogen peroxide （H2O2） and hydroxyl radicals. Activities of both enzymatic and non-enzymatic components of the antioxidant system and related growth parameters were studied in the roots of the salt tolerant rice variety FL478 and the sensitive variety IR29 in response to long term stress （12 d）induced by 50 mmol/L NaCI. The comparative study showed that FL478 maintained higher relative growth rate and lower Na＋/K＋ in the roots than IR29 due to a higher membrane stability index that effectively exclude Na＋. Lower TBARS （thiobarbituric acid reactive substance） content in FL478 roots indicated that its membrane was relatively unaffected by ROS despite high H2O2 content recorded under the salinity stress. Relatively higher superoxide dismutase activity along with a parallel increase in transcript level of superoxide dismutase （Os07g46990） in FL478 indicated that this protein might make a vital contribution to salt stress tolerance. Although the content of ascorbic acid remained unchanged in FL478, the activity of ascorbic peroxidases （APOXs） was reduced comparably in the both varieties. Transcriptomic data showed that a larger number of peroxidase genes were upregulated in FL478 compared to IR29 and several of which might provide engineering targets to improve rice salt tolerance.

Salinity Stress in Wheat:Effects,Mechanisms and Management Strategies

Salinity stress is a major threat to global food production and its intensity is continuously increasing because of anthropogenic activities.Wheat is a staple food and a source of carbohydrates and calories for the majority of people across the globe.However,wheat productivity is adversely affected by salt stress,which is associated with a reduction in germination,growth,altered reproductive behavior and enzymatic activity,disrupted photosynthesis,hormonal imbalance,oxidative stress,and yield reductions.Thus,a better understanding of wheat(plant)behavior to salinity stress has essential implications to devise counter and alleviation measures to cope with salt stress.Different approaches including the selection of suitable cultivars,conventional breeding,and molecular techniques can be used for facing salt stress tolerance.However,these techniques are tedious,costly,and labor-intensive.Management practices are still helpful to improve the wheat performance under salinity stress.Use of arbuscular mycorrhizal fungi,plant growth-promoting rhizobacteria,and exogenous application of phytohormones,seed priming,and nutrient management are important tools to improve wheat performance under salinity stress.In this paper,we discussed the effect of salinity stress on the wheat crop,possible mechanisms to deal with salinity stress,and management options to improve wheat performance under salinity conditions.

Salinity Stress Alleviation by Foliar Bio-Stimulant, Proline and Potassium Nutrition Promotes Growth and Yield Quality of Garlic Plant

Soil salinity is one of the major yield-limiting factors for crop production in many agricultural regions all over the world. Besides following efficient management practices at the field scale to reduce accumulation of salts in the effective root-zone, the effective use of treatments to alleviate the effects of salinity stress and improve crop salt tolerance is a promising solution to ensure crop production in such adverse conditions. A field experiment was carried out to investigate the effect of foliar spray with plant-based biostimulant (i.e. with and/or without 3% yeast extract), three levels of proline (0, 25, and 50 mM), and combined with potassium fertilizers, as potassium sulfate, 48% K2O (0, 50, and 100 kg/fed.) on growth promotion, chemical composition of garlic leaves, bulb quality parameters as well as yield and its components of garlic plant grown under moderate saline soil. Results revealed that the interaction between foliar spray with yeast extract at 3% and proline at 50 mM combined with proper K level at 100 kg/fed., was the best interaction treatment for increasing vegetative growth parameters, i.e. plant height, number of leaves per plant, and mineral contents (N, P, K, S, Ca and Mg in leaves), and proline content of garlic leaves after 135 days from planting time, total yield/fed., and garlic yield quality parameters at harvesting time. In conclusion, the detrimental effects of salinity stress can be alleviated by stress tolerance-inducing compounds, such as yeast extract and proline with proper application rate of K fertilization during the growing season of garlic crop.

Effects of acute salinity stress on the survival and prophenoloxidase system of Exopalaemon carinicauda

The ridgetail white prawn Exopalaemon carinicauda is a euryhaline shrimp species in the estuarine and coastal areas of China.In this study,survival rates,transcription levels of two prophenoloxidase system-related genes(Ec LGBP and Ecpro PO)and PO activity were determined quantitatively in juvenile and adult E.carinicauda under different salinity levels.The results showed that E.carinicauda juveniles could survive in a wider range of salinity conditions than adults.For juvenile E.carinicauda,the expression levels of Ec LGBP and Ec Pro PO were upregulated in low salinities and showed no significant difference at 20–40,while PO activities in low salinities were higher compared to those in high salinities.For adult E.carinicauda,the expression profiles of Ec LGBP and Ecpro PO had a different trend of up-regulation in salinity stress treatments and no obvious difference was observed in the gene expression levels and PO activity between 30 and 40.The salinity tolerance range of immunity for juvenile and adult E.carinicauda is 20–40 and 30–40,respectively.

Azospirillum brasilense and Saccharomyces cerevisiae as Alternative for Decrease the Effect of Salinity Stress in Tomato(Lycopersicon esculentum)Growth

The salinity stress is one of the most relevant abiotic stresses that affects the agricultural production.The present study was performed to study the improvement of the salt tolerance of tomato plants which is known for their susceptibility to salt stress.The present study aimed to assess to what extent strain Azospirillum brasilense(N040)and Saccharomyces cerevisiae improve the salt tolerance to tomato plants treated with different salt concentration.The inoculant strain A.brasilense(N040)was previously adapted to survive up to 7%NaCl in the basal media.A greenhouse experiment was conducted to evaluate the effect of this inoculation on growth parameter such as:plant height,root length,fresh and dry weight,fruits fresh weight,chlorophyll content,proline and total soluble sugar in tomato plants under salt stress condition.The results revealed that co-inoculation of Azospirillum brasilense(N040)and Saccharomyces cerevisiae significantly increased the level of proline(8.63 mg/g FW)and total soluble sugar(120 mg/g FW)of leaves under salinity condition comparing to non-inoculated plants(2.3 mg/g FW and 70 mg/g FW,respectively).Plants co-inoculated with adapted strain of A.brasilense and S.cerevisiae showed the highest significant(p<0.01)increase in fruit yield(1166.6 g/plant),plant high(115 cm)and roots length(52.6)compared whit un-inoculated control plants(42 g/pant,43.3 cm and 29.6 cm,respectively).In contrast,Na^(+)ion content was significantly decreased in the leaves of salt stressed plants treated with the A.brasilense(N040)and S.cerevisiae.Finally,the results showed that dual benefits provided by both A.brasilense(N040)and S.cerevisiae can provide a major way to improve tomato yields in saline soils.

Effect of Salinity Stress on Antioxidant Defense System of Niger (Guizotia abyssinica Cass.)

Salinity is one of the principal abiotic stresses that affect plant productivity by inducing osmotic stress, which in turn, causes oxidative stress. Plants respond to this oxidative stress by adjusting levels of antioxidants and associated components. 10-day old seedlings of Niger were evaluated for abiotic stress response in terms of antioxidants and antioxidant enzymes over 72 h in presence of up to 500 mM NaCl in combination with CaCl2. Stress markers: H2O2, lipid peroxidation, antioxidants;ASC and GSH and antioxidant enzymes such as POX, APX and GR were significantly elevated, while CAT was reduced. The response was concentration and time-dependent up to 300 mM NaCl and fluctuated beyond. Metabolic enzymes β-amylase and acid phosphatase exhibited moderate increase relative to controls. The parameters indicated tolerance of the plants to salinity up to 300 mM over 48 h.

Short-term Response of Photosynthesis and Chlorophyll Content to Salinity Stress in Two Mangrove Species:Aegiceras corniculatum and Kandelia candel

There were fewer comparative studies on the adaptability of mangrove plants with two different salt secretion mechanisms to salinity stress. In this study,the seedlings of mangrove plants Aegiceras corniculatum and Kandelia candel were selected as the research objects,and the methods of hydroponics with different salinity gradients were used. The salinity of 0‰,10‰,and 30‰ was applied respectively to simulate the adaptability of seedlings at low,moderate,and severe salinity stresses. Based on the results,the short-term responses of photosynthesis and chlorophyll content to salinity stress in two mangrove species with different salt secretion mechanisms were analyzed and discussed. The results show that A. corniculatum was more tolerant to10‰ salinity than K. candel,and the net photosynthetic rate(Pn),transpiration rate(Tr),stomatal conductance( Gs) and water use efficiency(WUE)were also relatively higher;both A. corniculatum and K. candel could acclimate the low salinity(0‰),but showed severe osmotic stress at 30‰ salinity;A. corniculatum was more sensitive to severe salinity(30‰) than K. candel. These results can be of help to provide a theoretical support for the selection of species for mangrove wetlands restoration and seedlings acclimatization in tidal flats.

Nanoparticle Treatments Based on Zinc Oxide and Moringa oleifera Leaf Extracts Alleviate Salinity Stress in Faba Bean (Vicia faba L.)

Salinity stress limits crop growth and productivity, including legumes in various regions worldwide. The impact of foliar-applied zinc nanoparticles (ZnNPs) and combined zinc nano-loaded with moringa extracts (ZnONPs) on salt tolerance in faba beans (cultivar, Giza-716) grown under saline soil (50 and 100 mM NaCl) was investigated. Moringa oleifera extract has been used as a chelating agent to synthesize zinc oxide nanoparticles. The crystalline structure, morphology, and chemical composition of ZnO nanoparticles were studied using various characterization techniques, including UV-visible spectroscopy (UV), Fourier Transform Infrared Analysis (FTIR), scanning electron microscopy (SEM), and X-ray diffraction (XRD). Morphological, chemical, and biochemical parameters of plants at 60 and 90 days after sowing were assessed. Salinity stress caused a remarkable reduction in growth traits, photosynthetic pigments and proline levels of the faba bean. Foliar spray with ZnNPs and ZnONPs on faba bean grown under saline soils promoted plant growth parameters (i.e., shoot length, numbers of leaves, relative water content, shoot and roots fresh and dry weights), photosynthetic pigments (Chl a, b, total chlorophyll, and carotenoids), proline and mineral elements (Na+, K+, Ca2+, and Zn2+) compared to control. However, at 100 mM NaCl, there were no significant variations in the mentioned parameters. This study suggested that there is potential for foliar spraying with ZnNPs and ZnONPs in improving growth parameters, photosynthesis efficiency and biochemical aspects of faba bean plants under saline conditions.

Effect of Salinity Stress on Growth and Yield of Forage Genotypes

Salinity is the major limiting factor for forage productivity in southwestern coastal region of Bangladesh. Some introduced forage cultivars have been shown promising adaptability in saline conditions. The objective of this study was to assess the productivity and measure the agronomic characteristics of several introduced grass species with different created soil salinity levels. This study was conducted at the net house of Dr. Purnendu Gain Field Laboratory, Agrotechnology Discipline, and Khulna University during the period from December 2017 to February 2018. The experiment was laid out in a factorial randomized complete block design with seven replications. The experiment consisted of two factor viz. soil salinity levels (S1 = 0.48, S2 = 5.8, S3 = 7.9, S4 = 9.4, S5 = 15 d·Sm−1) and thirteen forage genotypes. Salinity levels and forage genotypes significantly (p < 0.05) influence all the growth parameters and biomass yield. The growth parameters and yield gradually decreased with the advance of soil salinity level. The tallest plant height (109.85 cm) was found in S1 at 90 DAS while the shortest plant (24.53 cm) was obtained in S5 at 90 DAS. Soil salinity had a significant difference (p < 0.001) on plant height at 90 DAS. The highest numbers of tillers (3.36) were found in S1, whereas the lowest (0.48) was in S5 at 75 DAS. Soil salinity had a significant difference (p < 0.001) on Number of tillers at 75 DAS. The highest biomass wt. (29.14 g) was found in S1, while the lowest biomass wt. (3.52 g) was obtained in S5 at 60 DAS. Soil salinity had a significant difference (p < 0.001) on biomass wt. at 60 DAS. The highest dry matter% (DM%) (21.24%) was found in S4, while the lowest DM (18.74%) was obtained in S1 at 60 DAS. Soil salinity had a significant difference (p < 0.001) on dry matter% (DM%) wt. at 90 DAS. The tallest plant height (81.93 cm) was found in Pakchong, while the shortest plant (20.13 cm) was obtained in Endropogan at 60DAS. Soil salinity had a significant difference (p < 0.001) on plant height at 60 DAS. The highest numbers of tillers (3.07) were also found in Napier-3, whereas the lowest (0.80) was in H. Jaumbo at 75 DAS (S1 + S2 + S3 + S4 + S5). Soil salinity had a significant difference (p < 0.001) on Number of tillers at 75 DAS. The highest biomass wt. (38.60 g) was found in Pakchong, while the lowest biomass wt. (4.49 g) was obtained in Oats at 60 DAS. Soil salinity had a significant difference (p < 0.001) on biomass wt. at 60 DAS (S1 + S2 + S3 + S4 + S5). The highest (DM%) was found in Endropogan (24.68%), while the lowest DM (18.37%) was obtained Spelindida. Soil salinity had a significant difference (p < 0.001) on DM at 90 DAS. It can be concluded that Pakchong appears to be highly salt tolerant.

Grain Yield,Biomass Accumulation,and Leaf Photosynthetic Characteristics of Rice under Combined Salinity-Drought Stress

Simultaneous stresses of salinity and drought often coincide during rice-growing seasons in saline lands,primarily due to insufficient water resources and inadequate irrigation facilities.Consequently,combined salinity-drought stress poses a major threat to rice production.In this study,two salinity levels(NS,non-salinity;HS,high salinity)along with three drought treatments(CC,control condition;DJ,drought stress imposed at jointing;DH,drought stress imposed at heading)were performed to investigate their combined influences on leaf photosynthetic characteristics,biomass accumulation,and rice yield formation.Salinity,drought,and their combination led to a shortened growth period from heading to maturity,resulting in a reduced overall growth duration.Grain yield was reduced under both salinity and drought stress,with a more substantial reduction under the combined salinity-drought stress.The combined stress imposed at heading caused greater yield losses in rice compared with the stress imposed at jointing.Additionally,the combined salinity-drought stress induced greater decreases in shoot biomass accumulation from heading to maturity,as well as in shoot biomass and nonstructural carbohydrate(NSC)content in the stem at heading and maturity.However,it increased the harvest index and NSC remobilization reserve.Salinity and drought reduced the leaf area index and SPAD value of flag leaves and weakened the leaf photosynthetic characteristics as indicated by lower photosynthetic rates,transpiration rates,and stomatal conductance.These reductions were more pronounced under the combined stress.Salinity,drought,and especially their combination,decreased the activities of ascorbate peroxidase,catalase,and superoxide dismutase,while increasing the contents of malondialdehyde,hydrogen peroxide,and superoxide radical.Our results indicated a more significant yield loss in rice when subjected to combined salinity-drought stress.The individual and combined stresses of salinity and drought diminished antioxidant enzyme activities,inhibited leaf photosynthetic functions,accelerated leaf senescence,and subsequently lowered assimilate accumulation and grain yield.

ORF355 confers enhanced salinity stress adaptability to S-type cytoplasmic male sterility maize by modulating the mitochondrial metabolic homeostasis

Moderate stimuli in mitochondria improve wideranging stress adaptability in animals, but whether mitochondria play similar roles in plants is largely unknown. Here, we report the enhanced stress adaptability of S-type cytoplasmic male sterility(CMS-S) maize and its association with mild expression of sterilizing gene ORF355. A CMS-S maize line exhibited superior growth potential and higher yield than those of the near-isogenic N-type line in saline fields. Moderate expression of ORF355 induced the accumulation of reactive oxygen species and activated the cellular antioxidative defense system. This adaptive response was mediated by elevation of the nicotinamide adenine dinucleotide concentration and associated metabolic homeostasis. Metabolome analysis revealed broad metabolic changes in CMS-S lines, even in the absence of salinity stress. Metabolic products associated with amino acid metabolism and galactose metabolism were substantially changed, which underpinned the alteration of the antioxidative defense system in CMS-S plants. The results reveal the ORF355-mediated superior stress adaptability in CMS-S maize and might provide an important route to developing salt-tolerant maize varieties.

Soil microbial communities regulate the threshold effect of salinity stress on SOM decomposition in coastal salt marshes

Salinity stress is one of the critical environmental drivers of soil organic matter(SOM)decomposition in coastal ecosystems.Although the temperature sensitivity(Q_(10))of SOM decomposition has been widely applied in Earth system models to forecast carbon processes,the impact of salinity on SOM decomposition by restructuring microbial communities remains uncovered.Here,we conducted a microcosm experiment with soils collected from the coastal salt marsh in the Yellow River Estuary,which is subjected to strong dynamics of salinity due to both tidal flooding and drainage.By setting a gradient of salt solutions,soil salinity was adjusted to simulate salinity stress and soil carbon emission(CO_(2))rate was measured over the period.Results showed that as salinity increased,the estimated decomposition constants based on first-order kinetics gradually decreased at different temperatures.Below the 20‰salinity treatments,which doubled the soil salinity,Q_(10)increased with increasing salinity;but higher salinity constrained the temperature-related response of SOM decomposition by inhibiting microbial growth and carbon metabolisms.Soil bacteria were more sensitive to salinity stress than fungi,which can be inferred from the response of microbial beta-diversity to changing salinity.Among them,the phylotypes assigned to Gammaproteobacteria and Bacilli showed higher salt tolerance,whereas taxa affiliated with Alphaproteobacteria and Bacteroidota were more easily inhibited by the salinity stress.Several fungal taxa belonging to Ascomycota had higher adaptability to the stress.As the substrate was consumed with the incubation,bacterial competition intensified,but the fungal co-occurrence pattern changed weakly during decomposition.Collectively,these findings revealed the threshold effect of salinity on SOM decomposition in coastal salt marshes and emphasized that salt stress plays a key role in carbon sequestration by regulating microbial keystone taxa,metabolisms,and interactions.

Salinity Acclimation Induces Reduced Energy Metabolism,Osmotic Pressure Regulation and Transcriptional Reprogramming in Hypotrichida Ciliate Gastrostyla setifera

Coastal and estuarine protists are frequently exposed to salinity undulation.While the tolerance and stress responses of microalgae to salinity have been extensively studied,there have been scarce studies on the physiological response of heterotrophic protists to salinity stressing.In this study,we investigated the physiological response of the heterotrophic ciliate Gastrostyla setifera to a salinity of 3,via a transcriptomic approach.The first transcriptome of genus Gastrostyla was obtained utilizing a group of manually isolated ciliate individuals(cells)and RNA-seq technique.The completeness of the transcriptome was verified.Differentially expressed gene(DEG)analysis was performed among the transcriptomes of G.setifera acclimated in saline water(salinity 3)and those cultured in fresh water.The results demonstrated a significant alternation in gene transcription,in which the ciliate exhibits a transcripttomic acclimation in responding salinity stressing.The up-regulated DEGs were enriched in the pathways of cytoskeleton proteins,membrane trafficking,protein kinases and protein phosphatases.These may represent enhanced functions of ion transport,stress response and cell protections.Pathways involved in energy metabolism and biosynthesis were markedly down-regulated,reflecting decreased cell activity.Particularly,we detected significantly down-regulated genes involved in several pathways of amino acid catabolism,which may lead to accumulation of amino acids in the ciliate cell.Amino acid could act as compatible solutes in the cytoplasm to maintain the osmotic balance in saline water.Overall,this work is an initial exploration to the molecular basis of the heterotrophic protist responding to salinity stressing.The result sheds light on the mechanisms of enhancement of cell protection,reduction of cell activity,and osmotic pressure regulation in ciliates acclimated to salinity.

Plasticity of photorespiratory carbon concentration mechanism in Sedobassia sedoides(Pall.)Freitag&G.Kadereit under elevated CO_(2)concentration and salinity

Rising atmospheric CO_(2)(carbon dioxide)concentrations and salinization are manifestations of climate change that affect plant growth and productivity.Species with an intermediate C_(3)-C_(4)type of photosynthesis live in a wide range of precipitation,temperature,and soil quality,but are more often found in warm and dry habitats.One of the intermediate C_(3)-C_(4)photosynthetic type is C_(2)photosynthesis with a carbon concentration mechanism(CCM)that reassimilates CO_(2)released via photorespiration.However,the ecological significance under which C_(2)photosynthesis has advantages over C_(3)and C_(4)plants remains largely unexplored.Salt tolerance and functioning of CCM were studied in plants from two populations(P1 and P2)of Sedobassia sedoides(Pall.)Freitag&G.Kadereit Asch.species with C_(2)photosynthesis exposed to 4 d and 10 d salinity(200 mM NaCl)at ambient(785.7 mg/m^(3),aCO_(2)and elevated(1571.4 mg/m^(3),eCO_(2))CO_(2).On the fourth day of salinity,an increase in Na+content,activity catalase,and superoxide dismutase was observed in both populations.P2 plants showed an increase in proline content and a decrease in photosynthetic enzyme content:rubisco,phosphoenolpyruvate carboxylase(PEPC),and glycine decarboxylase(GDC),which indicated a weakening of C_(2)and C_(4)characteristics under salinity.Treatment under 10 d salinity led to an increased Na^(+)content and activity of cyclic electron flow around photosystem I(PSI CEF),a decreased content of K^(+)and GDC in both populations.P1 plants showed greater salt tolerance,which was assessed by the degree of reduction in photosynthetic enzyme content,PSI CEF activity,and changes in relative growth rate(RGR).Differences between populations were evident under the combination of eCO_(2)and salinity.Under long-term salinity and eCO_(2),more salt-tolerant P1 plants had a higher dry biomass(DW),which was positively correlated with PSI CEF activity.In less salt-tolerant P2 plants,DW correlated with transpiration and dark respiration.Thus,S.sedoides showed a high degree of photosynthetic plasticity under the influence of salinity and eCO_(2)through strengthening(P1 plants)and weakening C_(4)characteristics(P2 plants).

Integrative Multi-omics Analyses of Barley Rootzones under Salinity Stress Reveal Two Distinctive Salt Tolerance Mechanisms

The mechanisms underlying rootzone-localized responses to salinity during early stages of barley development remain elusive.In this study,we performed the analyses of multi-root-omes(transcriptomes,metabolomes,and lipidomes)of a domesticated barley cultivar(Clipper)and a landrace(Sahara)that maintain and restrict seedling root growth under salt stress,respectively.Novel generalized linear models were designed to determine differentially expressed genes(DEGs)and abundant metabolites(DAMs)specific to salt treatments,genotypes,or rootzones(meristematic Z1,elongation Z2,and maturation Z3).Based on pathway over-representation of the DEGs and DAMs,phenylpropanoid biosynthesis is the most statistically enriched biological pathway among all salinity responses observed.Together with histological evidence,an intense salt-induced lignin impregnation was found only at stelic cell wall of Clipper Z2,compared with a unique elevation of suberin deposition across Sahara Z2.This suggests two differential salt-induced modulations of apoplastic flow between the genotypes.Based on the global correlation network of the DEGs and DAMs,callose deposition that potentially adjusted symplastic flow in roots was almost independent of salinity in rootzones of Clipper,and was markedly decreased in Sahara.Taken together,we propose two distinctive salt tolerance mechanisms in Clipper(growth-sustaining)and Sahara(salt-shielding),providing important clues for improving crop plasticity to cope with deteriorating global soil salinization.

Altered seawater salinity levels affected growth and photosynthesis of Ulva fasciata(Ulvales, Chlorophyta)germlings

Seawater salinity is greatly influenced by tide, evaporation and rain falls. In this study, we investigated the growth and photosynthetic responses of zygote-derived Ulva fasciata Delile germlings to short-term （minutes） and prolonged （days） exposure to different salinity gradients, to evaluate the effect of salinity variation on the early stage of life history in this seaweed. The results showed that, the maximum net photosynthetic rates （NPRm） of U. fasciata germlings was observably decreased in desalted （25 and 15） and high （45） salinity seawater in short-term exposure tests （in minutes）. However, after 30 min, the photosynthesis activity in medium salinity （25） was maintained at a relative high level （above 70%）. After 8 d prolonged culture, the photosynthesis and mean relative growth rate （RGR） of germlings were all markedly lowered, whereas the malondialdehyde （MDA） contents increased as the salinity desalted from 34 to 15. The salinity decrease from 34 to 25 had no significant effect on the RGR, but obviously influenced the morphology of the germlings. High salinity level （45） significantly depressed the RGR and photosynthesis of U. fasciata germlings, while it notably increased the MDA contents. The results showed that the salinity elevation had more detrimental effects on Ulvafasciata germlings than salinity decrease did. The germlings grown at the salinity seawater levels from 25 to 34, performed preferable photosynthetic acclimation both in temporary and prolonged culture. Broad salinity tolerance from 25 to 34 in U. fasciata germlings may have partly evolved as a response to regular diurnal tides.

Comparative Study on Growth Performance of Transgenic(Over-Expressed OsNHX1) and Wild-Type Nipponbare under Different Salinity Regimes

Transgenic Nipponbare which over-expressed a Na＋/H~ antiporter gene OsNHX1 was used to compare its growth performance, water status and photosynthetic efficiency with its wild type under varying salinity regimes. Chlorophyll content, quantum yield and photosynthetic rate were measured to assess the impact of salinity stress on photosynthetic efficiency for transgenic and wild-type Nipponbare. Effects of salinity on water status and gas exchange to both lines were studied by measuring water use efficiency, instantaneous transpiration rate and stomatal conductance. Dry shoot weight and leaf area were determined after three months of growth to assess the impacts of salinity on the growth of those two lines. Our study showed that both lines were affected by salinity stress, however, the transgenic line showed higher photosynthetic efficiency, better utilization of water, and better growth due to low transpiration rate and stomatal conductance. Reduction of photosynthetic efficiency exhibited by the wild-type Nipponbare was correlated to its poor growth under salinity stress.

Effect of Salinity on the Survival, Ions and Urea Modulation in Red-eared Slider(Trachemys scripta elegans)

To understand the tolerance to salinity and osmoregulation of the introduced Trachemys scripta elegans, the salinity stress of four groups （salinity 5‰, 15‰, 25‰ and control group） were conducted. Inorganic ions, osmotic pressure, glucose and aldosterone of blood and urine in T. s. elegans （BW： 125.60 ±19.84 g） were analyzed at 30 d, 60 d and 90 d stress. The results showed that： 1） inorganic ions concentration of blood and urine increased with ambient salinity, which indicated that high influx of ions was combined with higher outflow when exposed to saline water in T. s. elegans. However, blood aldosterone decreased with increasing salinity, which indicated that an increased sodium intake resulting in a diminished aldosterone production. However, with elapsed time, inorganic ions in urine decreased, which indicated that inorganic ions in blood would be accumulated, and Na^＋ and Cl^- in the plasma inevitably build up to harmful levels, at last death was happening when T. s. elegans was exposed to salinity 25 during 90 d salinity stress; 2） blood osmotic pressure increased as ambient salinity increased, it would reach 400 mOsm/kg in the group of salinity 25, which was about 1.5 fold of the control group. Higher blood osmotic pressure was due to both higher blood ions and urea concentrations. There may be another mechanism to avoid an excess of NaCl together with an important loss of water using one of the end-products of nitrogen metabolism; 3） blood glucose in each group except the group of salinity 5 decreased with time elapsed and with salinity increased. Therefore, we can conclude that T. s. elegans is an osmoregulator that limits the entry of Na^＋ and Cl^-, but can also tolerate certain degrees of increases in plasma Na^＋ and Cl^-. When ambient salinity was lower than 15‰, T. s. elegans can increase blood osmotic pressure by balancing the entry of NaCl with the secretion of aldosterone decreased, and by accumulating blood urea for osmoregulation effectors, and survive for at least three months. These results could provide theoretical basis for salinity tolerance and the invasion on physiological mechanism for T. s. elegans.