Synergistic effects of carbon cycle metabolism and photosynthesis in Chinese cabbage under salt stress

Chinese cabbage(Brassica rapa ssp. pekinensis) has a long cultivation history and is one of the vegetable crops with the largest cultivation area in China. However, salt stress severely damages photosynthesis and hormone metabolism, nutritional balances, and results in ion toxicity in plants. To better understand the mechanisms of salt-induced growth inhibition in Chinese cabbage, RNA-seq and physiological index determination were conducted to explore the impacts of salt stress on carbon cycle metabolism and photosynthesis in Chinese cabbage. Here, we found that the number of thylakoids and grana lamellae and the content of starch granules and chlorophyll in the leaves of Chinese cabbage under salt stress showed a time-dependent response, first increasing and then decreasing. Chinese cabbage increased the transcript levels of genes related to the photosynthetic apparatus and carbon metabolism under salt stress, probably in an attempt to alleviate damage to the photosynthetic system and enhance CO_(2) fixation and energy metabolism. The transcription of genes related to starch and sucrose synthesis and degradation were also enhanced;this might have been an attempt to maintain intracellular osmotic pressure by increasing soluble sugar concentrations. Soluble sugars could also be used as potential reactive oxygen species(ROS) scavengers, in concert with peroxidase(POD)enzymes, to eliminate ROS that accumulate during metabolic processes. Our study characterizes the synergistic response network of carbon metabolism and photosynthesis under salt stress.

Genome-Wide Exploration of the Grape GLR Gene Family and Differential Responses of VvGLR3.1 and VvGLR3.2 to Low Temperature and Salt Stress

Grapes,one of the oldest tree species globally,are rich in vitamins.However,environmental conditions such as low temperature and soil salinization significantly affect grape yield and quality.The glutamate receptor(GLR)family,comprising highly conserved ligand-gated ion channels,regulates plant growth and development in response to stress.In this study,11 members of the VvGLR gene family in grapes were identified using whole-genome sequence analysis.Bioinformatic methods were employed to analyze the basic physical and chemical properties,phylogenetic trees,conserved domains,motifs,expression patterns,and evolutionary relationships.Phylogenetic and collinear analyses revealed that the VvGLRs were divided into three subgroups,showing the high conservation of the grape GLR family.These members exhibited 2 glutamate receptor binding regions(GABAb and GluR)and 3-4 transmembrane regions(M1,M2,M3,and M4).Real-time quantitative PCR analysis demonstrated the sensitivity of all VvGLRs to low temperature and salt stress.Subsequent localization studies in Nicotiana tabacum verified that VvGLR3.1 and VvGLR3.2 proteins were located on the cell membrane and cell nucleus.Additionally,yeast transformation experiments confirmed the functionality of VvGLR3.1 and VvGLR3.2 in response to low temperature and salt stress.Thesefindings highlight the significant role of the GLR family,a highly conserved group of ion channels,in enhancing grape stress resistance.This study offers new insights into the grape GLR gene family,providing fundamental knowledge for further functional analysis and breeding of stress-resistant grapevines.

Effects of Different Arbuscular Mycorrhizal Fungi on Physiology of Viola prionantha under Salt Stress

Arbuscular mycorrhizal(AM)fungi distribute widely in natural habits and play a variety of ecological functions.In order to test the physiological response to salt stress mediated by different AM fungi,Viola prionantha was selected as the host,the dominant AM fungus in the rhizosphere of V.philippica growing in Songnen saline-alkali grassland,Rhizophagus irregularis,and their mixtures were used as inoculants,and NaCl stress was applied after the roots were colonized.The results showed that V.philippica could be colonized by AM fungi in the field and the colonization rate ranged from 73.33%to 96.67%,and Claroideoglomus etunicatum was identified as the dominant AM fungi species in the rhizosphere of V.philippica by morphology combined with sequencing for AM fungal AML1/AML2 target.Inoculation with both the species resulted in the formation of mycorrhizal symbiosis(the colonization rate was more than 70%)and AM fungi significantly enhanced plants’tolerance to salt stress of varying magnitude.Higher activity of antioxidant enzymes and augmented levels of proline and other osmoregulators were observed in AM plants.The content of MDA in CK was higher than that in the inoculations with the stress of 100,200,and 250 mM.All indices except soluble protein content and MDA content were significantly correlated with AM fungal colonization indices.The analysis for different AM fungal effects showed that the mixtures and R.irregularis worked even better than C.etunicatum.These results will provide theoretical support for the exploration and screening of salt-tolerant AM fungi species and also for the application of AM-ornamental plants in saline-alkali urban greening.

The lectin gene TRpL1 of tetraploid Robinia pseudoacacia L.response to salt stress

Lectins are natural proteins in animals,plants,and microorganisms and can be divided into 12 families.These lectins play important roles in various environmental stresses.Some polyploid plants show tolerance to environmental stresses and to insect pests.However,the mechanism of stress tolerance is unclear.Tetraploid Robinia pseudoacacia(4×)under salt stress showed higher tolerance than diploid R.pseudoacacia(2×).As lectin can improve stress tolerance,it was questioned whether the stress resistance of polyploid plants was related to the lectin protein.In this study,salt resistance of lectin gene TRpL1 was verified by its over-expression in plants.In addition,salt resistance of lectin protein by E.coli strains was detected.The data revealed that the over-expression transgenic plants of TRpL1 showed better salt tolerance than control plants under salt stress,and the TRpL1-expressing strain also grew better in the medium with added NaCl.Therefore,tetraploid plants can resist salt stress through TRpL1 protein regulation.

Identification of novel salt stress-responsive microRNAs through sequencing and bioinformatic analysis in a unique halophilic Dunaliella salina strain

Dunaliella salina is a classic halophilic alga.However,its molecular mechanisms in response to high salinity at the post transcriptional level remain unknown.A unique halophilic alga strain,DS-CN1,was screened from four D.salina strains via cell biological,physiological,and biochemical methods.High-throughput sequencing of small RNAs(sRNAs)of DS-CN1 in culture medium containing 3.42-mol/L NaCl(SS group)or 0.05-mol/L NaCl(CO group)was performed on the BGISEQ-500 platform.The annotation and sequences of D.salina sRNAs were profiled.Altogether,44 novel salt stress-responsive microRNAs(miRNAs)with a relatively high C content,with the majority of them being 24 nt in length,were identified and characterized in DS-CN1.Twenty-one differentially expressed miRNAs(DEMs)in SS and CO were screened via bioinformatic analysis.A total of 319 putative salt stress-related genes targeted(104 overlapping genes)by novel miRNAs in this alga were screened based on our previous transcriptome sequencing research.Furthermore,these target genes were classified and enriched by GO and KEGG pathway analysis.Moreover,5 novel DEMs(dsa-mir3,dsa-mir16,dsa-mir17,and dsa-mir26 were significantly upregulated,and dsa-mir40 was significantly downregulated)and their corresponding 10 target genes involved in the 6 significantly enriched metabolic pathways were verified by quantitative real-time PCR.Next,their regulatory relationships were comprehensively analyzed.Lastly,a unique salt stress response metabolic network was constructed based on the novel DEM-target gene pairs.Taken together,our results suggest that 44 novel salt stress-responsive microRNAs were identified,and 4 of them might play important roles in D.salina upon salinity stress and contribute to clarify its distinctive halophilic feature.Our study will shed light on the regulatory mechanisms of salt stress responses.

GhSCL4 Acts as a Positive Regulator in Both Transgenic Arabidopsis and Cotton during Salt Stress

GRAS transcription factors play important roles in plant abiotic stress response,but their characteristics and functions in cotton have not been fully investigated.A cotton SCL4/7 subgroup gene in the GRAS family,GhSCL4,was found to be induced by NaCl treatments.Nuclear localization and transactivation activity of GhSCL4 indicate its potential role in transcriptional regulation.Transgenic Arabidopsis thaliana over-expressing GhSCL4 showed enhanced resistance to salt and osmotic stress.What’s more,the transcript levels of salt stress-induced genes(AtNHX1 and AtSOS1)and oxidation-related genes(AtAPX3 and AtCSD2)were more highly induced in the GhSCL4 over-expression lines than in wild type after salt treatment.Furthermore,silencing of GhSCL4 resulted in reduced salt tolerance in cotton caused by reactive oxygen species(ROS)enrichment under salt treatment,and antioxidant enzyme activities were accordingly significantly reduced in GhSLC4-silenced lines.These results indicated that GhSCL4 enhances salt tolerance of cotton by detoxifying ROS.In addition,the transient expression assay confirmed an interactive relationship between GhSCL4 and GhCaM7,which indicated that salt tolerance conferred by GhSCL4 might be associated with salt-induced Ca^(2+)/CaM7-mediated signaling.Taken together,GhSCL4 acts as a positive regulator in cotton during salt stress that is potentially useful for engineering salt-tolerant cotton.

Proteome-wide identification of S-sulfenylated cysteines response to salt stress in Brassica napus root

Reactive oxygen species(ROS)play a key role in a variety of biological processes,such as the perception of abiotic stress,the integration of different environmental signals,and the activation of stress response networks.Salt stress could induce an increased ROS accumulation in plants,disrupting intracellular redox homeostasis,leading to posttranslational modifications(PTMs)of specific proteins,and eventually causing adaptive changes in metabolism.Here,we performed an iodoTMT-based proteomic approach to identify the sulfenylated proteins in B.napus root responsing to salt stress.Totally,1348 sulfenylated sites in 751 proteins were identified and these proteins were widely existed in different cell compartments and processes.Our study revealed that proteins with changed abundance and sulfenylation level in B.napus root under salt stress were mainly enriched in the biological processes of ion binding,glycolysis,ATP binding,and oxidative stress response.This study displays a landscape of sulfenylated proteins response to salt stress in B.napus root and provides some theoretical support for further understanding of the molecular mechanisms of redox regulation under salt stress in plants.

Chlorophyll Fluorescence Response of Persimmon Plants under Salt Stress

[Objectives]To study the photosynthetic response mechanism of persimmon seedlings to salt stress.[Methods]The chlorophyll fluorescence parameters of Diospyros virginiana and Diospyros lotus seedlings under 4%salt stress were studied by pot culture salt control method,including the minimal fluorescence(F_(0)),maximum fluorescence(F_(m)),potential activity of PS II(F_(v)/F_(0)),maximum photochemical efficiency of PS II(F_(v)/F_(m)),electron transport rate(ETR),actual photochemical efficiency of PS II(Y II),and photochemical quenching coefficient(q_(p)).[Results]Under 4%salt stress,the maximum fluorescence(F_(m)),maximum photochemical efficiency of PS II(F v/F m),and photochemical quenching coefficient(q_(p))of two persimmon plants decreased with time.The potential activity of PS II(F_(v)/F_(0)),actual photochemical efficiency of PS II(Y_(II)),and electron transport rate(ETR)decreased under salt stress.[Conclusions]This study indicates that the PS II reaction center in the persimmon leaves was damaged and the electron transport at the acceptor side was damaged under salt stress.It is expected to lay a foundation for the analysis of salt-tolerance mechanism of persimmon plants.

Effect of Exogenous Gibberellin on Wheat Seed Germination under Salt Stress

[Objectives]In this experiment,wheat seeds were treated with different concentrations of gibberellin and different concentrations of salt solution to study the change of germination index of wheat seeds.[Methods]The germination rate,germination potential and germination index of wheat seeds were measured by routine methods,and the effect of exogenous gibberellin on germination of wheat seeds under salt stress was observed.[Results]The germination rate,germination potential and germination index of wheat seeds under salt stress were significantly increased after exogenous treatment of 0.25 and 0.50 g/L gibberellin within the range of salt concentration gradient.However,when the concentration of gibberellin was too high,it would inhibit the germination of seeds.[Conclusions]Appropriate concentration of gibberellin can effectively alleviate the stress caused by salt on wheat seed germination.In this experiment,the best concentration of gibberellin to alleviate salt stress was 0.25 g/L.

Changes of Proline Content,Activity,and Active Isoforms of Antioxidative Enzymes in Two Alfalfa Cultivars Under Salt Stress

The plants of two elfalfa （Medicago sativa L.） cultivars differing in salt tolerance were subjected to three salt treatments, 70, 140, and 210 mM NaCl for 7 days. Root, shoot, and leaf growths were inhibited by increased salt treatments in both cultivars, and at 140 and 210 mM salt treatments, Zhongmu 1 had significantly higher root, shoot, and leaf dry weights per plant than Deft. The malondialdehyde （MDA） accumulation in Deft was considerably greater than in Zhongmu 1, indicating a higher degree of lipid peroxidation at 140 and 210 mM salt treatments. The changes in the activity and active isoforms of antioxidant enzymes such as superoxide dismutase （SOD, EC 1.15.1.1）, catalase （CAT, EC 1.11.1.6）, peroxidase （POD, EC 1.11.1.7）, and ascorbate peroxidase （APOX, EC 1.11,1.11）, accumulation of free proline, and rate of lipid peroxidation in leaves of two alfalfa cultivars were also investigated. After stress, the activity and active isoforms of antioxidative enzymes were altered and the extent of alteration varied between the cultivar Deft and Zhongmu 1. The proline accumulation in Deft was considerably greater than in Zhongmu 1 at 210 mM salt treatment. This indicated that proline accumulation may be the result, instead of the cause, of salt tolerance.

Effects of salt stress on rice growth, development characteristics, and the regulating ways： A review

Rice （Oryza safiva L.） is highly susceptible to the rhizosphere salinity than other cereals. High sensitivity has been ob- served, mainly at vegetative and reproductive stages in rice. It is the duty of plant physiologists to comprehend the growth, development, and physiological processes of rice plants under stress. This paper includes the overview of rice growth and developmental processes influenced by salt stress and the regulation pathways involved in these processes. It also includes the promising salt tolerance strategies, i.e., genetic modification techniques, agronomic practices to improve rice growth, yield; and role of phytohormones and their management, especially inhibition of ethylene biosynthesis by using inhibitors 1-methylcyclopropene （1-MCP）. Rice cultivation may be a first choice for improvement of salt tolerance through plant growth regulators and improved cultivation techniques. This study will significantly improve the understanding toward low rice grain yield and poor rice resistance under salt stress and will also stream scientific knowledge for effective utilization of salt affected soils by using different regulating ways.

Effects of Cinnamic Acid on Bacterial Community Diversity in Rhizosphere Soil of Cucumber Seedlings Under Salt Stress

To investigate the effects of a plant autotoxin, cinnamic acid, on bacterial communities in the rhizosphere soil of cucumber seedlings under salt stress, we used cucumber as the experimental material, cinnamic acid as the autotoxin, and NaCl to apply salt stress. Bacterial communities in the rhizosphere soil were analyzed using polymerase chain reaction （PCR）, denaturing gradient gel electrophoresis （DGGE）, and clone sequencing. Salt stress decreased the diversity of bacterial species in rhizosphere soil of cucumber seedlings at several growth stages. Cinnamic acid exacerbated the effects of salt stress at high concentrations, but alleviated its effects at low concentrations. Cloning and sequencing results indicated that DGGE bands amplified from soil samples showed high homology to uncultured bacterial species. Cinnamic acid at 50 mg kg^-1 soil improved cucumber growth and was the most effective treatment to alleviate the effects of salt stress on bacterial communities.

Effect of Ascorbic Acid and Silicium on Photosynthesis, Antioxidant Enzyme Activity, and Fatty Acid Contents in Canola Exposure to Salt Stress

The effects of exogenous ascorbic acid and silicium on leaf fresh weigh, seed yield, photosynthesis, changes of the activities of major antioxidant enzymes, nitrate reductase activity, proline accumulation, chlorophyll content, and fatty acid composition were investigated in salt-stressed canola. A hydroponic pot experiment was conducted based on randomized complete block design, factorial arrangement was used with 16 combinations of salinity stress （0, 100, 200, and 300 mmol L-1 NaC1）, ascorbic acid （0 and 30 mmol L-1）, and silicium （2 and 4 mmol L-1 from potassium silicate） with three replicates. The results showed that salinity significantly decreased leaf area and leaf fresh weight, seed yield, photosynthesis, nitrate reductase activity, chlorophyll content, and seed protein percentage. Conversely, respiration, antioxidant enzymes activity, proline accumulation, and linolenic acid percentage increased due to salt stress. Ascorbic acid application improved photosynthesis and seed yield and mitigated antioxidant enzyme activity. In addition, nitrate reductase activity and chlorophyll a and b were positively affected by ascorbic acid. Regarding silicium application, that was found that leaf area, leaf fresh weight, seed yield and photosynthesis, ascorbate peroxidase activity, nitrate reductase activity, and chlorophyll content increased, while respiration decreased. Furthermore, silicium had not significant effect on antioxidant enzyme activity. In general, ascorbic acid and silicium were involved in the defensive mechanisms against salinity stress and it can be suggested that, ascorbic acid and silicium application had positive effect on canola growth under conditions of salt stress.

Nitrogen in Relation to Photosynthetic Capacity and Accumulation of Osmoprotectant and Nutrients in Brassica Genotypes Grown Under Salt Stress

Different strategies of the application of nutrients are required to overcome the adverse effects of mustard （Brassica juncea L.） in response to NaCl stress. The objective of the present study was to determine if different added levels of nitrogen （N） in growth medium could alleviate the adverse effects of salt stress on photosynthetic capacity and accumulation of osmoprotectants and nutrients. 14 days mustard seedlings of salt-sensitive （cv. Chuutki） and salt-tolerant （cv. Radha） genotypes were fed with： （i） 0 mmol L^-1 NaCl ＋ 0 mg N kg^-1 sand （control）, （ii） 90 mmol L^-1 NaCl ＋ 30 mg N kg^-1 sand, （iii） 90 mmol L^-1 NaCl ＋60 mg N kg^-1 sand, （iv） 90 mmol L^-1 NaCl ＋90 mg N kg^-1 sand and （v） 90 mmol L^-1NaCl＋ 120 mg N kg^-1 sand. Under the condition of salinity stress, N application caused a significant ameliorative effect on both genotypes with respect to growth attributes [fresh weight （FW） and dry weight （DW）] and physio-biochemical parameters [percent water content （WC）, net photosynthetic rate （PN）, stomatal conductance （gs）, total chlorophyll （Ch1）, carbonic anhydrase （CA） activity and malondialdehyde （MDA）, nitrogen （N）, potassium （K） and sodium （Na） contents, and K/Na ratio] and yield attributes （number of pods/plant, seeds/pod and seed yield/plant）. The salt-tolerant genotype exhibited maximum value for growth, physio-biochemical and yield attributes at 60 mg N kg 1 sand than that of salt-sensitive genotype. These results suggest that application of N may ameliorate most of the attributes and prove to be a physiological remedy to increase the tolerance against the ill effects of salt stress in Brassicas.

Effect of acid phosphatase produced by Trichoderma asperellum Q1 on growth of Arabidopsis under salt stress

Salt stress is a major environmental factor that inhibits crop growth.Trichoderma spp.are the most efficient biocontrol fungi and some of the strains can stimulate plant growth.Phosphate solubilization is known as one of the main mechanisms in promoting plant growth,but the underlying mechanisms of phosphate solubilization in the salinity still need to be explored.The Trichoderma asperellum Q1 isolated and identified in our lab is a beneficial rhizosphere biocontrol fungus with a high phosphate solubilization activity.It could produce acid and alkaline phosphatases when using insoluble organic phosphorus as the sole phosphorus source,the salt stress increased the phosphorus-solubilization ability of the strain and the activities of the two enzymes.Furthermore,an acid phosphatase was purified from the fermentation broth by ammonium sulphate precipitation,ion-exchange,and gel filtration chromatography.Its molecular weight was 55 k Da as determined by SDS-PAGE.The purified acid phosphatase was used to investigate growth performance of Arabidopsis thaliana by plate assay and the result showed that it contributed to Arabidopsis growth by transforming organic phosphate into a soluble inorganic form under salt stress.To our knowledge,this is the first report on acid phosphatase purification from T.asperellum and its function in regulation of plant growth under salt stress.

Response and adaptation to the accumulation and distribution of photosynthetic product in peanut under salt stress

To clarify the response and adaptability of peanut under salt stress,Huayu 25 was used as the material,and non-salt stress(CK),0.15% salt stress(S1),and 0.3% salt stress(S2) were applied as three treatments.The study analysed the effects of salt stress on photosynthetic characteristics,photosynthetic substances accumulation and distribution as well as the ecological adaptability of peanuts.The results showed that net photosynthetic rate(Pn),SPAD value,leaf area,and peanut yield were reduced under salt stress.Pn in CK was 13.71 and 28.72% higher than that in S1 and S2 at the 50 th day after planting,respectively.At the same growth period,the SPAD value among treatments was ranked as follows: CK>S1>S2.The 100-pod mass,100-kernel mass,kernel rate to pod,and pod mass per plant were reduced under salt stress,and the trend was CK>S1>S2.The distribution proportion of dry matter in different organs of peanut plant was changed to adapt to such stress.Roots under salt stress intensively distributed in a 0-40 cm soil layer for salt resistance.Dry mass proportion in stems and pods increased during the vegetative stage and early period of reproductive stage,respectively.The maximum growth rates of the pod volume,pod dry weight,and seed kernel dry weight all declined,and the pod and kernel volume at harvest were reduced,improving the seed plumpness under salt stress.This finding could be useful in growing peanut in saline soil.

Arabidopsis LOS5 Gene Enhances Chilling and Salt Stress Tolerance in Cucumber

Low temperature and high salinity are the major abiotic stresses that restrict cucumber growth and production, breeding materials with multiple abiotic resistance are in greatly need. Here we investigated the effect of introducing the LOS5 gene, a key regulator of ABA biosynthesis in Arabidopsis thaliana, under the stress-responsive RD29A promoter into cucumber （Cucumis sativus L. cv. S516）. We found that T1 RD29A-LOS5 transgenic lines have enhanced tolerance to cold and salt stresses. Specifically, transgenic lines exhibited dwarf phenotypes with reduced leaf number, shorter internode, decreased length of the biggest leaf, fewer female flowers, shorter fruit neck and lower vitamin C （Vc）. The increased cold tolerance can be reflected from the significantly decreased cold index, the reduced electrolyte leakage index and the MDA content upon cold treatment as compared to those in the control. This may result from the accumulation of internal ABA, soluble sugars and proline, and the enhanced activities of protective enzymes superoxide dismutase （SOD）, peroxidase （POD） and catalase （CAT） in the transgenic lines. Under salt treatment, the transgenic lines exhibited increased germination index, vigor index, more lateral roots and increased root fresh weight. Moreover, RD29A-LOS5 transgenic plants displayed quicker responses in salt stress than that in low-temperature stress.

The NAC-like transcription factor Si NAC110 in foxtail millet(Setaria italica L.) confers tolerance to drought and high salt stress through an ABA independent signaling pathway

Foxtail millet（Setaria italica（L.）P.Beauv）is a naturally stress tolerant crop.Compared to other gramineous crops,it has relatively stronger drought and lower nutrition stress tolerance traits.To date,the scope of functional genomics research in foxtail millet（S.italic L.）has been quite limited.NAC（NAM,ATAF1/2 and CUC2）-like transcription factors are known to be involved in various biological processes,including abiotic stress responses.In our previous foxtail millet（S.italic L.）RNA seq analysis,we found that the expression of a NAC-like transcription factor,SiNAC110,could be induced by drought stress;additionally,other references have reported that SiNAC110 expression could be induced by abiotic stress.So,we here selected SiNAC110 for further characterization and functional analysis.First,the predicted SiNAC110 protein encoded indicated SiNAC110 has a conserved NAM（no apical meristem）domain between the 11–139 amino acid positions.Phylogenetic analysis then indicated that SiNAC110 belongs to subfamily III of the NAC gene family.Subcellular localization analysis revealed that the SiNAC110-GFP fusion protein was localized to the nucleus in Arabidopsis protoplasts.Gene expression profiling analysis indicated that expression of SiNAC110 was induced by dehydration,high salinity and other abiotic stresses.Gene functional analysis using SiNAC110 overexpressed Arabidopsis plants indicated that,under drought and high salt stress conditions,the seed germination rate,root length,root surface area,fresh weight,and dry weight of the SiNAC110 overexpressed lines were significantly higher than the wild type（WT）,suggesting that the SiNAC110 overexpressed lines had enhanced tolerance to drought and high salt stresses.However,overexpression of SiN AC110 did not affect the sensitivity of SiNAC110 overexpressed lines to abscisic acid（ABA）treatment.Expression analysis of genes involved in proline synthesis,Na＋/K＋transport,drought responses,and aqueous transport proteins were higher in the SiNAC110overexpressed lines than in the WT,whereas expression of ABA-dependent pathway genes did not change.These results indicated that overexpression of SiNAC110 conferred tolerance to drought and high salt stresses,likely through influencing the regulation of proline biosynthesis,ion homeostasis and osmotic balance.Therefore,SiNAC110 appears to function in the ABA-independent abiotic stress response pathway in plants.

Isolation and Characterization of the Wheat cDNA Fragments Involved in Salt Stress

cDNA-AFLP(amplified fragment length polymorphism) is used to isolate genes differentiallyexpressed in salt-stressed and unstressed wheat lines RH8706-49 and H8706-34 derivedfrom a single seed, representing a salt-stress resistant (SR) and salt-stress sensitive(SS) line, respectively. About 88.1% cDNA fragment are expressed in all the four samples,11.9% are different between the samples. 68 cDNA fragments were cloned, of which 35 weresubject to sequence analysis. Database searches indicate that 11 cDNA fragment show highhomology to known genes, which mainly include proteins related to ion transport, signaltransduction and oxidative stress. The remaining 24 cDNA show no detectable homology toknown genes, suggesting that they probably represent novel genes.

Overaccumulation of glycine betaine makes the function of the thylakoid membrane better in wheat under salt stress

Wheat(Triticum aestivum L.) lines T1, T4, and T6 were genetically modified to increase glycine betaine(GB) synthesis by introduction of the BADH(betaine aldehyde dehydrogenase, BADH)gene from mountain spinach(Atriplex hortensis L.). These transgenic lines and WT of wheat(T. aestivum L.) were used to study the effect of increased GB synthesis on wheat tolerance to salt stress. Salt stress due to 200 mmol L-1Na Cl impaired the photosynthesis of the four wheat lines, as indicated by declines in net photosynthetic rate(Pn), stomatal conductance(Gs),maximum photochemical efficiency of PSII(Fv/Fm), and actual photochemical efficiency of PSII(ФPSII) and an increase in intercellular CO2concentration(Ci). In comparison with WT, the effect of salinity on the three transgenic lines was mild. Salt stress caused disadvantageous changes in lipids and their fatty acid compositions in the thylakoid membrane of the transgenic lines and WT. Under salt stress, the three transgenic lines showed slightly higher chlorophyll and carotenoid contents and higher Hill reaction activities and Ca2+-ATPase activity than WT. All the results suggest that overaccumulation of GB resulting from introduction of the BADH gene can enhance the salt tolerance of transgenic plants, especially in the protection of the components and function of thylakoid membranes, thereby making photosynthesis better. Changes in lipids and fatty acid compositions in the thylakoid membrane may be involved in the increased salt stress tolerance of the transgenic lines.