High pH Stress Research Articles

Influence of Strain on Current Densities and Stress Corrosion Cracking Growth Rates in X65 Pipeline Steel

High pH stress corrosion cracking (SCC) in gas pipelines has been seen to grow along an incline angle rather than perpendicular to the outer surface. Crack tip strain enhanced electrochemistry has been previously postulated as a reason for the inclination, and recent computer simulations that take this effect into account produce realistic crack paths. This study attempts to determine the effect of strain on the electrochemical response of X65 steel, and the impact that the strain has on growth rates for inclined SCC. Potentiodynamic tests were conducted on X65 tensile specimens with residual plastic strain or in situ elastic strain. An increase of the current density up to 300% was observed within the SCC potential range. Computer simulations were also conducted to show the qualitative effect of this increase in current density on the growth rate, and results indicated that inclined SCC could grow to 50% wall thickness faster than straight SCC if the current density along the inclined angle is 20% higher...

Selection of Reference Genes for qRT-PCR Analysis of Gene Expression in Stipa grandis during Environmental Stresses.

Stipa grandis P. Smirn. is a dominant plant species in the typical steppe of the Xilingole Plateau of Inner Mongolia. Selection of suitable reference genes for the quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR) is important for gene expression analysis and research into the molecular mechanisms underlying the stress responses of S. grandis. In the present study, 15 candidate reference genes (EF1 beta, ACT, GAPDH, SamDC, CUL4, CAP, SNF2, SKIP1, SKIP5, SKIP11, UBC2, UBC15, UBC17, UCH, and HERC2) were evaluated for their stability as potential reference genes for qRT-PCR under different stresses. Four algorithms were used: GeNorm, NormFinder, BestKeeper, and RefFinder. The results showed that the most stable reference genes were different under different stress conditions: EF1beta and UBC15 during drought and salt stresses; ACT and GAPDH under heat stress; SKIP5 and UBC17 under cold stress; UBC15 and HERC2 under high pH stress; UBC2 and UBC15 under wounding stress; EF1beta and UBC17 under jasmonic acid treatment; UBC15 and CUL4 under abscisic acid treatment; and HERC2 and UBC17 under salicylic acid treatment. EF1beta and HERC2 were the most suitable genes for the global analysis of all samples. Furthermore, six target genes, SgPOD, SgPAL, SgLEA, SgLOX, SgHSP90 and SgPR1, were selected to validate the most and least stable reference genes under different treatments. Our results provide guidelines for reference gene selection for more accurate qRT-PCR quantification and will promote studies of gene expression in S. grandis subjected to environmental stress.

2D modelling of inclined intergranular stress corrosion crack paths

AbstractInclined high pH stress corrosion cracking (SCC) is a type of intergranular environmental cracking in gas pipelines, which differs from typical SCC by propagating at an angle from the wall direction. Investigations of Australian and Canadian inclined SCC colonies have not provided a clear indicator of a cause for the abnormal crack growth direction. This paper addresses the possibility of crack tip strain enhanced electrochemistry causing the inclination. Potentiodynamic tests were conducted to quantify the influence of strain on the electrochemistry, and strain was found to increase current density up to 300% in the SCC region. A model was developed that incorporates crack tip strain driven SCC growth, which showed good agreement with field grown cracks, and the aspect ratio of the grains was shown to have an effect on the inclination angle. The results indicate that crack tip strain enhanced electrochemistry is a plausible cause for inclined SCC.

Genome-wide recruitment profiling of transcription factor Crz1 in response to high pH stress.

BackgroundExposure of the budding Saccharomyces cerevisiae to an alkaline environment produces a robust transcriptional response involving hundreds of genes. Part of this response is triggered by an almost immediate burst of calcium that activates the Ser/Thr protein phosphatase calcineurin. Activated calcineurin dephosphorylates the transcription factor (TF) Crz1, which moves to the nucleus and binds to calcineurin/Crz1 responsive gene promoters. In this work we present a genome-wide study of the binding of Crz1 to gene promoters in response to high pH stress.ResultsEnvironmental alkalinization promoted a time-dependent recruitment of Crz1 to 152 intergenic regions, the vast majority between 1 and 5 min upon stress onset. Positional evaluation of the genomic coordinates combined with existing transcriptional studies allowed identifying 140 genes likely responsive to Crz1 regulation. Gene Ontology analysis confirmed the relevant impact of calcineurin/Crz1 on a set of genes involved in glucose utilization, and uncovered novel targets, such as genes responsible for trehalose metabolism. We also identified over a dozen of genes encoding TFs that are likely under the control of Crz1, suggesting a possible mechanism for amplification of the signal at the transcription level. Further analysis of the binding sites allowed refining the consensus sequence for Crz1 binding to gene promoters and the effect of chromatin accessibility in the timing of Crz1 recruitment to promoters.ConclusionsThe present work defines at the genomic-wide level the kinetics of binding of Crz1 to gene promoters in response to alkaline stress, confirms diverse previously known Crz1 targets and identifies many putative novel ones. Because of the relevance of calcineurin/Crz1 in signaling diverse stress conditions, our data will contribute to understand the transcriptional response in other circumstances that also involve calcium signaling, such as exposition to sexual pheromones or saline stress.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-3006-6) contains supplementary material, which is available to authorized users.

Regulation of the Na+/K+-ATPase Ena1 Expression by Calcineurin/Crz1 under High pH Stress: A Quantitative Study.

Regulated expression of the Ena1 Na+-ATPase is a crucial event for adaptation to high salt and/or alkaline pH stress in the budding yeast Saccharomyces cerevisiae. ENA1 expression is under the control of diverse signaling pathways, including that mediated by the calcium-regulatable protein phosphatase calcineurin and its downstream transcription factor Crz1. We present here a quantitative study of the expression of Ena1 in response to alkalinization of the environment and we analyze the contribution of Crz1 to this response. Experimental data and mathematical models substantiate the existence of two stress-responsive Crz1-binding sites in the ENA1 promoter and estimate that the contribution of Crz1 to the early response of the ENA1 promoter is about 60%. The models suggest the existence of a second input with similar kinetics, which would be likely mediated by high pH-induced activation of the Snf1 kinase.

High-pH inclined stress corrosion cracking in Australian and Canadian gas pipeline X65 steels

High-pH stress corrosion cracking is a form of environmental degradation of gas pipeline steels. The crack path is intergranular by nature and typically perpendicular to the maximum applied (hoop) stress (i.e. perpendicular to the pipe outer surface). Some unusual instances of cracks have been observed in Canadian and Australian X65 pipes, where cracks grow away from the perpendicular for considerable distances. This paper presents a comparative study in terms of crack morphology, mechanical properties and crystallographic texture for these Australian and Canadian pipe steels. It is shown that the crack morphologies are quite similar, the main difference being the angle at which the cracks propagate into the material. This difference could be explained by the different through-wall texture and grain aspect ratio measured in the two materials. The interdependency of crack tip plasticity, crack tip electrochemistry and anisotropy in microstructural texture seems to heavily affect the resulting inclined crack path.

GsERF6, an ethylene-responsive factor from Glycine soja, mediates the regulation of plant bicarbonate tolerance in Arabidopsis.

This is an original study focus on ERF gene response to alkaline stress. GsERF6 functions as transcription factor and significantly enhanced plant tolerance to bicarbonate (HCO 3 (-) ) in transgenic Arabidopsis . Alkaline stress is one of the most harmful, but little studied environmental factors, which negatively affects plant growth, development and yield. The cause of alkaline stress is mainly due to the damaging consequence of high concentration of the bicarbonate ion, high-pH, and osmotic shock to plants. The AP2/ERF family genes encode plant-specific transcription factors involved in diverse environmental stresses. However, little is known about their physiological functions, especially in alkaline stress responses. In this study, we functionally characterized a novel ERF subfamily gene, GsERF6 from alkaline-tolerant wild soybean (Glycine soja). In wild soybean, GsERF6 was rapidly induced by NaHCO3 treatment, and its overexpression in Arabidopsis enhanced transgenic plant tolerance to NaHCO3 challenge. Interestingly, GsERF6 transgenic lines also displayed increased tolerance to KHCO3 treatment, but not to high pH stress, implicating that GsERF6 may participate specifically in bicarbonate stress responses. We also found that GsERF6 overexpression up-regulated the transcription levels of bicarbonate-stress-inducible genes such as NADP-ME, H (+)-Ppase and H (+)-ATPase, as well as downstream stress-tolerant genes such as RD29A, COR47 and KINI. GsERF6 overexpression and NaHCO3 stress also altered the expression patterns of plant hormone synthesis and hormone-responsive genes. Conjointly, our results suggested that GsERF6 is a positive regulator of plant alkaline stress by increasing bicarbonate ionic resistance specifically, providing a new insight into the regulation of gene expression under alkaline conditions.

A review of modelling high pH stress corrosion cracking of high pressure gas pipelines

Modelling of intergranular stress corrosion cracking (SCC) in pipelines is an important field of study as predictive techniques are integral to pipeline integrity and management. An inclination of the SCC propagation direction has been observed for some pipelines, which is not predictable using existing models as they assume perpendicular crack growth. A review has been conducted to identify the applicable techniques from existing models, as well as the gaps in current knowledge. Existing work in crack growth rates, stress formulations and microstructural representations are reviewed. Mechanical dependency of the electrochemical response is identified as a gap and proposed for inclusion in a model alongside the other areas reviewed.

Transcriptome analysis of Enterococcus faecalis in response to alkaline stress.

Enterococcus faecalis is the most commonly isolated species from endodontic failure root canals; its persistence in treated root canals has been attributed to its ability to resist high pH stress. The goal of this study was to characterize the E. faecalis transcriptome and to identify candidate genes for response and resistance to alkaline stress using Illumina HiSeq 2000 sequencing. We found that E. faecalis could survive and form biofilms in a pH 10 environment and that alkaline stress had a great impact on the transcription of many genes in the E. faecalis genome. The transcriptome sequencing results revealed that 613 genes were differentially expressed (DEGs) for E. faecalis grown in pH 10 medium; 211 genes were found to be differentially up-regulated and 402 genes differentially down-regulated. Many of the down-regulated genes found are involved in cell energy production and metabolism and carbohydrate and amino acid metabolism, and the up-regulated genes are mostly related to nucleotide transport and metabolism. The results presented here reveal that cultivation of E. faecalis in alkaline stress has a profound impact on its transcriptome. The observed regulation of genes and pathways revealed that E. faecalis reduced its carbohydrate and amino acid metabolism and increased nucleotide synthesis to adapt and grow in alkaline stress. A number of the regulated genes may be useful candidates for the development of new therapeutic approaches for the treatment of E. faecalis infections.

Impact of high pH stress on yeast gene expression: A comprehensive analysis of mRNA turnover during stress responses

Environmental alkalinisation represents a stress condition for yeast Saccharomyces cerevisiae, to which this organism responds with extensive gene expression remodelling. We show here that alkaline pH causes an overall decrease in the transcription rate (TR) and a fast destabilisation of mRNAs, followed by a more prolonged stabilisation phase. In many cases, augmented mRNA levels occur without the TR increasing, which can be attributed to mRNA stabilisation. In contrast, the reduced amount of mRNAs is contributed by both a drop in the TR and mRNA stability. A comparative analysis with other forms of stress shows that, unlike high pH stress, heat-shock, osmotic and oxidative stresses present a common transient increase in the TR. An analysis of environmentally-responsive (ESR) genes for the four above stresses suggests that up-regulated genes are governed mostly by TR changes and complex transient bidirectional changes in mRNA stability, whereas the down-regulated ESR gene set is driven by mRNA destabilisation and a lowered TR. In all the studied forms of stress, mRNA stability plays an important role in ESR. Overall, changes in mRNA levels do not closely reflect the rapid changes in the TR and stability upon exposure to stress, which highlights the existence of compensatory mechanisms.

Searching for Growth Conditions for Optimized Expression of Recombinant Proteins in Escherichia coli by Using Two‐Dimensional NMR Spectroscopy

Escherichia coli has been widely used as a host to produce recombinant proteins. However, because of its prokaryotic nature, it often fails to produce eukaryotic proteins in their native or correctly folded forms. To devise a systematic way to find such a condition that produces a large amount of correctly folded proteins, we chose to perturb the composition of intracellular metabolites by imposing different stresses such as the addition of sorbitol, NaCl, pH, and ethanol, and to monitor which metabolites showed the largest differences in the case of successful protein production. We profiled the metabolites under stresses by using two‐dimensional NMR spectroscopy, and identified 39 metabolites after the protein production phase. We found that mild NaCl stress increased the yield of the target protein. Mildly high pH stress also helped in producing more of the target protein, and there is likely a connection between the isoelectric point of the target protein and the pH of medium for a higher yield. Exogenous sorbitol appeared to have been used to produce an osmoprotectant (trehalose) or direct energy source (glucose); thus it is advised that its use should not include isotopic labeling. Mild ethanol stress did not cause any significant change either in the metabolite profile or in the target protein production. We hope this work might shed light on how to improve production of the target protein by adjusting the external environment.

Study on relieving effects of exogenous SNP,Spd on Belamcanda chinensis under salt-alkalline stress

The study is aimed to provide the theoretical basis for exploiting and utilization of salt-alkaline soil and cultivating Belamcanda chinensis. In this study, we exerted exogenous substances SNP, Spd to relieve the damage of the mixing salt-alkaline stress on B. chinensis seedling which is NaCl, Na2SO4, NaHCO3 and Na2CO3 four kinds of salt molar ratio of 9: 1: 9: 1, salt concentration of 100 mmol x L(-1). The result illustrated that high pH stress is a major factor caused the salt-alkaline stress, the interaction between time and the concentration of each, treatment was observed, what is more, there are synergies between the salt and alkali stress. The content of B. chinensis seedling leaves' membrane peroxidation index (MDA, O2-*) and metabolites (soluble protein, soluble sugars, organic acids) are showing an upward trend in varying degrees under 100 mmol x L(-1) salt-alkaline stress. It is effective to reduce the content of MDA and O2-*. and improve the levels of metabolites, in which the SNP (0.05 mmol x L(-1)) and Spd (0.5 mmol x L(-1)) to alleviate damage effects is the best. Therefore we can hold the conclusion that SNP and Spd can effectively mitigate the damage of B. chinensis seedling on salt-alkaline stress, improve the resistance ability of B. chinensis seedling which can provide the scientific basis for the utilization of salt-alkaline soil, and the cultivation of B. chinensis.

Coregulated Expression of the Na+/Phosphate Pho89 Transporter and Ena1 Na+-ATPase Allows Their Functional Coupling under High-pH Stress

The yeast Saccharomyces cerevisiae has two main high-affinity inorganic phosphate (Pi) transporters, Pho84 and Pho89, that are functionally relevant at acidic/neutral pH and alkaline pH, respectively. Upon Pi starvation, PHO84 and PHO89 are induced by the activation of the PHO regulon by the binding of the Pho4 transcription factor to specific promoter sequences. We show that PHO89 and PHO84 are induced by alkalinization of the medium with different kinetics and that the network controlling Pho89 expression in response to alkaline pH differs from that of other members of the PHO regulon. In addition to Pho4, the PHO89 promoter is regulated by the transcriptional activator Crz1 through the calcium-activated phosphatase calcineurin, and it is under the control of several repressors (Mig2, Nrg1, and Nrg2) coordinately regulated by the Snf1 protein kinase and the Rim101 transcription factor. This network mimics the one regulating expression of the Na(+)-ATPase gene ENA1, encoding a major determinant for Na(+) detoxification. Our data highlight a scenario in which the activities of Pho89 and Ena1 are functionally coordinated to sustain growth in an alkaline environment.

Biochemical and molecular characterization of potential phosphate-solubilizing bacteria in acid sulfate soils and their beneficial effects on rice growth.

A study was conducted to determine the total microbial population, the occurrence of growth promoting bacteria and their beneficial traits in acid sulfate soils. The mechanisms by which the bacteria enhance rice seedlings grown under high Al and low pH stress were investigated. Soils and rice root samples were randomly collected from four sites in the study area (Kelantan, Malaysia). The topsoil pH and exchangeable Al ranged from 3.3 to 4.7 and 1.24 to 4.25 cmolc kg−1, respectively, which are considered unsuitable for rice production. Total bacterial and actinomycetes population in the acidic soils were found to be higher than fungal populations. A total of 21 phosphate-solubilizing bacteria (PSB) including 19 N2-fixing strains were isolated from the acid sulfate soil. Using 16S rRNA gene sequence analysis, three potential PSB strains based on their beneficial characteristics were identified (Burkholderia thailandensis, Sphingomonas pituitosa and Burkholderia seminalis). The isolated strains were capable of producing indoleacetic acid (IAA) and organic acids that were able to reduce Al availability via a chelation process. These PSB isolates solubilized P (43.65%) existing in the growth media within 72 hours of incubation. Seedling of rice variety, MR 219, grown at pH 4, and with different concentrations of Al (0, 50 and 100 µM) was inoculated with these PSB strains. Results showed that the bacteria increased the pH with a concomitant reduction in Al concentration, which translated into better rice growth. The improved root volume and seedling dry weight of the inoculated plants indicated the potential of these isolates to be used in a bio-fertilizer formulation for rice cultivation on acid sulfate soils.

Microstructural and mechanical factors influencing high pH stress corrosion cracking susceptibility of low carbon line pipe steel

Several adjacent gas pipe sections were obtained from the field. These pipe sections had nominally identical manufacturing, construction, coating and operational conditions. Some sections were unaffected by stress corrosion cracking (SCC), whereas surrounding sections were affected by SCC. Slight differences in mechanical and microstructural properties were found between the two types of section. Residual stress/strain and hardness close to the outer surface of the pipes and high angle boundary fraction values were lower for the non-cracked pipe sections. Predominant 〈110〉//ND texture was also found at the outer surface of the non-cracked pipe sections. These characteristics lead to a lower crack growth rate in laboratory SCC experiments. These features being mainly a result of the line pipe steel manufacturing operations, appropriate metallurgical processes leading to low residual stress (6.2%YS), relatively low fraction of high angle boundaries (about 0.75) and predominant {110}〈110〉 texture in the material (or in the near surface) are expected to greatly improve the stress corrosion cracking resistance of line pipe steels on the field.

The Role of Residual Stresses in Circumferential Welding Repairs of Pipelines in SCC Susceptibility

The main objective of the present study is to measure the residual stresses in the circumferential welding joints of X52 pipeline steel with multiple welding repairs, and then relate these residual stresses to study the influence on the high pH stress corrosion cracking (SCC) susceptibility. Four conditions of shielded metal arc welding (SMAW) repairs of the girth weld were evaluated. The residual stresses were measured through X-ray diffraction (XRD) on the internal side of the pipe in longitudinal and circumferential direction. Residual stresses in the circumferential and longitudinal direction reach values of about 98 and 74% of the yielding strength (360 MPa) respectively. The effect of residuals stresses in the high pH-SCC susceptibility of X52 pipeline steel was evaluated through slow strain rate tests (SSRT) in a simulated soil solution. Relation between SCC index and residual stresses on the SCC susceptibility was analyzed. Results of SCC index taking account the ratios obtained from the mechanical properties of the welding joints evaluate (containing different levels of residual stresses) showed good SCC resistance. It was observed that increasing the magnitude of residual stresses, the SCC susceptibility increases. For all the SSRT specimens the failure occurs in the base metal and heat affected zone (HAZ) interface.

Physiological and transcriptomic analyses of the thermophilic, aceticlastic methanogen Methanosaeta thermophila responding to ammonia stress.

The inhibitory effects of ammonia on two different degradation pathways of methanogenic acetate were evaluated using a pure culture (Methanosaeta thermophila strain PT) and defined co-culture (Methanothermobacter thermautotrophicus strain TM and Thermacetogenium phaeum strain PB), which represented aceticlastic and syntrophic methanogenesis, respectively. Growth experiments with high concentrations of ammonia clearly demonstrated that sensitivity to ammonia stress was markedly higher in M. thermophila PT than in the syntrophic co-culture. M. thermophila PT also exhibited higher sensitivity to high pH stress, which indicated that an inability to maintain pH homeostasis is an underlying cause of ammonia inhibition. Methanogenesis was inhibited in the resting cells of M. thermophila PT with moderate concentrations of ammonia, suggesting that the inhibition of enzymes involved in methanogenesis may be one of the major factors responsible for ammonia toxicity. Transcriptomic analysis revealed a broad range of disturbances in M. thermophila PT cells under ammonia stress conditions, including protein denaturation, oxidative stress, and intracellular cation imbalances. The results of the present study clearly demonstrated that syntrophic acetate degradation dominated over aceticlastic methanogenesis under ammonia stress conditions, which is consistent with the findings of previous studies on complex microbial community systems. Our results also imply that the co-existence of multiple metabolic pathways and their different sensitivities to stress factors confer resiliency on methanogenic processes.

Effects of pH stress on antioxidant system enzyme activities and gene expression of Fenneropenaeus chinensis

Chinese shrimp,Fenneropenaeus chinensis,is an important mariculture species in China.Recently de-teriorated pond environment due to intensive culture caused increased incidence of stress-induced diseases.It is well known that environmental stress can induce oxidative stress.However,there is little information about the effects of pH changes on antioxidant system of Chinese shrimp.In this study,Chinese shrimps were exposed to water of pH7.0 and 9.0 for 148 h and pH8.2 was set as control.Total antioxidation activity(T-AOC),anti-superoxide anion activity,catalase(CAT) activity and the expression CAT,peroxiredoxin(Prx) gene were analyzed in gill,hepatopancreas,muscle and haemocytes of Chinese shrimp after 0 h,3 h,12 h,24 h,48 h,72 h,96 h,120 h and 148 h exposure.The T-AOC,anti-superoxide anion activity,CAT activity and the gene expression of CAT in different tissues increased within 12-14 h of pH stress.However,they were inhibited in the extending periods of pH stress time.The Prx gene expression in heaptopancreas and muscle gradually increased,but de-creased in gill and haemocytes with pH stress time prolonging.The enzyme activities and gene expression of an-tioxidant system in gills first reached its highest level in pH 9.0 group,faster than other tissues in 9.0 group.And the antioxidant enzyme activities in hepatopancreas in pH 7.0 group changed faster than in other tissues.The re-sults indicate that the antioxidant enzyme activities and gene expression of Chinese shrimp were induced by short-term pH stress which is the response to oxidative stress,while they were inhibited with pH stress time pro-longing.It was shown that long time neutral and alkaline-induced oxidative stress probably caused the antioxidant defense system injury in Chinese shrimp.Gills and hepatopancreas could be the sensitive tissues to high and low pH stress,respectively.

The General Stress Response Factor EcfG Regulates Expression of the C-2 Hopanoid Methylase HpnP in Rhodopseudomonas palustris TIE-1

Lipid molecules preserved in sedimentary rocks facilitate the reconstruction of events that have shaped the evolution of the Earth's biosphere. A key limitation for the interpretation of many of these molecular fossils is that their biological roles are still poorly understood. Here, we use Rhodopseudomonas palustris TIE-1 to identify factors that induce biosynthesis of 2-methyl hopanoids (2-MeBHPs), progenitors of 2-methyl hopanes, one of the most abundant biomarkers in the rock record. This is the first dissection of the regulation of hpnP, the gene encoding the C-2 hopanoid methylase, at the molecular level. We demonstrate that EcfG, the general stress response factor of alphaproteobacteria, regulates expression of hpnP under a variety of challenges, including high temperature, pH stress, and presence of nonionic osmolytes. Although higher hpnP transcription levels did not always result in higher amounts of total methylated hopanoids, the fraction of a particular kind of hopanoid, 2-methyl bacteriohopanetetrol, was consistently higher in the presence of most stressors in the wild type, but not in the ΔecfG mutant, supporting a beneficial role for 2-MeBHPs in stress tolerance. The ΔhpnP mutant, however, did not exhibit a growth defect under the stress conditions tested except in acidic medium. This indicates that the inability to make 2-MeBHPs under most of these conditions can readily be compensated. Although stress is necessary to regulate 2-MeBHP production, the specific conditions under which 2-MeBHP biosynthesis is essential remain to be determined.

CDNA cloning and expression profile analysis of an ATP-binding cassette transporter in the hepatopancreas and intestine of shrimp Fenneropenaeus chinensis

ATP-binding cassette (ABC) transporters are integral membrane proteins which carry diverse substrates across biological membranes. In this study, we report the cloning of a full-length, 2122-bp cDNA sequence encoding a gene of the ABC transporter subfamily G (ABCG) from the shrimp Fenneropenaeus chinensis. The deduced protein, FcABCG, contains 633 amino acid residues with a theoretical molecular weight of 70.57kDa. Phylogenetic analysis showed that the FcABCG clusters with the shrimp Litopenaeus vannamei ABCG in the same clade and is more closely related to the insect ABC transporter/white proteins than to the ABCG2 of the fish Salmo salar. High-level mRNA expression of FcABCG was detected in the tissues of hepatopancreas and intestine using a real-time quantitative reverse transcriptase PCR. Furthermore, exposure to alkaline pH stress conditions and norfloxacin diets result in the activation of the FcABCG gene in F. chinensis. These results suggest that the ABCG transporter of F. chinensis might play a role in coping high pH stress and in exporting xenobiotics.