Expression Of Β-glucuronidase Gene Research Articles

Irinotecan-gut microbiota interactions and the capability of probiotics to mitigate Irinotecan-associated toxicity

BackgroundIrinotecan is a chemotherapeutic agent used to treat a variety of tumors, including colorectal cancer (CRC). In the intestine, it is transformed into SN-38 by gut microbial enzymes, which is responsible for its toxicity during excretion.ObjectiveOur study highlights the impact of Irinotecan on gut microbiota composition and the role of probiotics in limiting Irinotecan-associated diarrhea and suppressing gut bacterial β-glucuronidase enzymes.Material and methodsTo investigate the effect of Irinotecan on the gut microbiota composition, we applied 16S rRNA gene sequencing in three groups of stool samples from healthy individuals, colon cancer, and Irinotecan treated patients (n = 5/group). Furthermore, three Lactobacillus spp.; Lactiplantibacillus plantarum (L. plantarum), Lactobacillus acidophilus (L. acidophilus), Lacticaseibacillus rhamnosus (L. rhamnosus) were used in a single and mixed form to in-vitro explore the effect of probiotics on the expression of β-glucuronidase gene from E. coli. Also, probiotics were introduced in single and mixed forms in groups of mice before the administration of Irinotecan, and their protective effects were explored by assessing the level of reactive oxidative species (ROS) as well as studying the concomitant intestinal inflammation and apoptosis.ResultsThe gut microbiota was disturbed in individuals with colon cancer and after Irinotecan treatment. In the healthy group, Firmicutes were more abundant than Bacteriodetes, which was the opposite in the case of colon-cancer or Irinotecan treated groups. Actinobacteria and Verrucomicrobia were markedly present within the healthy group, while Cyanobacteria were noted in colon-cancer and the Irinotecan-treated groups. Enterobacteriaceae and genus Dialister were more abundant in the colon-cancer group than in other groups. The abundance of Veillonella, Clostridium, Butryicicoccus, and Prevotella were increased in Irinotecan-treated groups compared to other groups. Using Lactobacillus spp. mixture in mice models significantly relieved Irinotecan-induced diarrhea through the reduction of both β-glucuronidase expression and ROS, in addition to guarding gut epithelium against microbial dysbiosis and proliferative crypt injury.ConclusionsIrinotecan-based chemotherapy altered intestinal microbiota. The gut microbiota participates greatly in determining both the efficacy and toxicity of chemotherapies, of which the toxicity of Irinotecan is caused by the bacterial ß-glucuronidase enzymes. The gut microbiota can now be aimed and modulated to promote efficacy and decrease the toxicity of chemotherapeutics. The used probiotic regimen in this study lowered mucositis, oxidative stress, cellular inflammation, and apoptotic cascade induction of Irinotecan.

Nuclear localization signal peptides enhance genetic transformation of Dunaliella salina.

Dunaliella salina (D. salina) expression system shows a very attractive application prospect, but it currently has a technical bottleneck, namely the low or unstable expression of recombinant proteins. Given the characteristics of cell-penetrating peptides or/and nuclear localization signal (NLS) peptides, this study is the first attempt to improve the transformation rate of foreign gene with trans-activating transcriptional (TAT) protein or/and NLS peptides. Using salt gradient method, exogenous plasmids were transferred into D. salina cells with TAT or TAT/NLS complexes simultaneously. The β-glucuronidase gene expression was identified by means of histochemical stain and RT-qPCR detection. Through observation with light microscope, TAT-mediating cells exhibit an apparent cytotoxicity even at ratios of 0.5, no significant toxicity was noted in the TAT/plasmid/NLS complex group. It is obvious that with the addition of peptides the toxicity decreases significantly. Histochemical staining showed that the transformants presented blue color under light microscope, but the negative control and blank control are not. Furthermore, based on a TAT/plasmids ratio of 4 with 10µg NLS peptides mediation, RT-qPCR results demonstrated that the transcripts of target gene were increased by 269 times than that of control group. This study demonstrated that combination of TAT and NLS peptides can significantly improve the transformation rate and expression level of foreign gene in D. salina system. It offers a promising way for promoting the application and development of D. salina bioreactor.

3-Phenyllactic acid is converted to phenylacetic acid and induces auxin-responsive root growth in Arabidopsis plants.

Many microorganisms have been reported to produce compounds that promote plant growth and are thought to be involved in the establishment and maintenance of symbiotic relationships. 3-Phenyllactic acid (PLA) produced by lactic acid bacteria was previously shown to promote root growth in adzuki cuttings. However, the mode of action of PLA as a root-promoting substance had not been clarified. The present study therefore investigated the relationship between PLA and auxin. PLA was found to inhibit primary root elongation and to increase lateral root density in wild-type Arabidopsis, but not in an auxin signaling mutant. In addition, PLA induced IAA19 promoter fused β-glucuronidase gene expression, suggesting that PLA exhibits auxin-like activity. The inability of PLA to promote degradation of Auxin/Indole-3-Acetic Acid protein in a yeast heterologous reconstitution system indicated that PLA may not a ligand of auxin receptor. Using of a synthetic PLA labeled with stable isotope showed that exogenously applied PLA was converted to phenylacetic acid (PAA), an endogenous auxin, in both adzuki and Arabidopsis. Taken together, these results suggest that exogenous PLA promotes auxin signaling by conversion to PAA, thereby regulating root growth in plants.

Cytosolic Glutamine Synthetase GS1;3 Is Involved in Rice Grain Ripening and Germination.

Ammonium is combined with glutamate to form glutamine. This reaction is catalyzed by glutamine synthetase (GS or GLN). Plants harbor several isoforms of cytosolic GS (GS1). Rice GS1;3 is highly expressed in seeds during grain filling and germination, suggesting a unique role in these processes. This study aimed to investigate the role of GS1;3 for rice growth and yield. Tos17 insertion lines for GS1;3 were isolated, and the nitrogen (N), amino acid, and ammonium contents of GS1;3 mutant grains were compared to wild-type grains. The spatiotemporal expression of GS1;3 and the growth and yield of rice plants were evaluated in hydroponic culture and the paddy field. Additionally, the stable isotope of N was used to trace the foliar N flux during grain filling. Results showed that the loss of GS1;3 retarded seed germination. Seeds of GS1;3 mutants accumulated glutamate but did not show a marked change in the level of phytohormones. The expression of GS1;3 was detected at the beginning of germination, with limited promoter activity in seeds. GS1;3 mutants showed a considerably decreased ripening ratio and decreased N efflux in the 12th leaf blade under N deficient conditions. The β-glucuronidase gene expression under control of the GS1;3 promoter was detected in the vascular tissue and aleurone cell layer of developing grains. These data suggest unique physiological roles of GS1;3 in the early stage of seed germination and grain filling under N deficient conditions in rice.

Creation of a genetic vector carrying a synthesis bacterial protein gene CAS9 for plant genome editing

Aim. To create a genetic construct carrying the bacterial protein Cas9 gene, the reporter β-glucuronidase gus gene, as well as the marker phosphinotricin-N-acetyltransferase bar gene for plant genome editing. Methods. Molecular-biological, biotechnological, microbiological and bioinformatic methods were used in the study; Golden Gate molecular cloning method was used to create genetic constructs. Results. The genetic construct pSPE2053 which carries the Cas9 endonuclease gene, the gus and bar genes was created; the assembly correctness of all vector elements was confirmed by polymerase chain reaction; the construct was transferred to Escherichia coli and Agrobacterium tumefaciens cells; β-glucuronidase gene expression was verified by histochemical analysis after Nicotiana rustica L transient genetic transformation. Conclusions. The created genetic construct can be used to edit the plant genome for both stable and transient genetic transformation to accumulate recombinant Cas9 protein. The guide RNA sequences may be subsequently transferred into such plants using either stable or transient genetic transformation or traditional crossing methods.
 Keywords: cloning, genetic construction, gus and bar genes, Cas9 endonuclease protein, transient expression.

The Single-Stranded DNA-Binding Protein WHIRLY1 Represses WRKY53 Expression and Delays Leaf Senescence in a Developmental Stage-Dependent Manner in Arabidopsis

Leaf senescence in plants involves both positive and negative transcriptional regulation. In this work, we show evidence for the single-stranded DNA-binding protein WHIRLY1 (WHY1) that functions as an upstream suppressor of WRKY53 in a developmental stage-dependent manner during leaf senescence in Arabidopsis (Arabidopsis thaliana). The why1 mutant displayed an early-senescence phenotype. In this background, the expression levels of both WRKY53 and the senescence-associated protease gene SAG12 increased. WHY1 bound to the sequence region that contains an elicitor response element motif-like sequence, GNNNAAATT, plus an AT-rich telomeric repeat-like sequence in the WRKY53 promoter in in vivo and in vitro mutagenesis assays as well as in a chromatin immunoprecipitation assay. This binding to the promoter of WRKY53 was regulated in a developmental stage-dependent manner, as verified by chromatin immunoprecipitation-polymerase chain reaction assay. This direct interaction was further determined by a transient expression assay in which WHY1 repressed β-GLUCURONIDASE gene expression driven by the WRKY53 promoter. Genetic analysis of double mutant transgenic plants revealed that WHY1 overexpression in the wrky53 mutant (oeWHY1wrky53) had no effect on the stay-green phenotype of the wrky53 mutant, while a WHY1 knockout mutant in the wrky53 mutant background (why1wrky53) generated subtle change in the leaf yellow/green phenotype. These results suggest that WHY1 was an upstream regulator of WRKY53 during leaf senescence.

Stability of β-glucuronidase gene expression in transgenic Tricyrtis hirta plants after two years of cultivation

Transgenic plants of Tricyrtis hirta carrying the intron-containing β-glucuronidase (GUS) gene under the control of the CaMV35S promoter have been cultivated for two years. Four independent transgenic plants produced flowers 1–2 years after acclimatization, and all of them contained one copy of the transgene as indicated by inverse polymerase chain reaction (PCR) analysis. All the four transgenic plants showed stable expression of the gus gene in leaves, stems, roots, tepals, stamens and pistils as indicated by histochemical and fluorometric GUS assays, although differences in the GUS activity were observed among different organs of each transgenic plant. No apparent gus gene silencing was observed in transgenic T. hirta plants even after two years of cultivation.

Factors affecting delivery and transient expression of β-glucuronidase gene in Dendrobium Sonia protocorm-like-body

The effect of the biolistic device parameters and other factors affecting delivery and expression of uidA gene in Dendrobium Sonia was investigated. Three week old protocorm like body (PLB) were bombarded with gold microparticles coated with pAHC 25 plasmid harbouring the uidA gene which encodes β -glucuronidase. The factors investigated were the helium pressure, target distance, macrocarrier flight distance to stopping screen, distance from stopping screen to target tissues, vacuum pressure, gold microparticles size, spermidine and calcium on DNA precipitation, and the number of bombardments. Two days after bombardment, the PLB were subjected to histochemical GUS assay, and transient GUS activity was recorded as blue spots using a Leica stereomicroscope. All the factors tested showed significant effects (p<0.05) on the delivery of DNA and expression of the uidA gene in Dendrobium PLB except for calcium. Surviving PLBs were able to grow and regenerate normally into plantlets. Keywords: biolistic transformation, orchid, Dendrobium , protocorm like body, -glucuronidase assay

Optimization of Agrobacterial (Agrobacterium tumefaciens) Transformation of Maize Embryogenic Callus

The method for genetic transformation of maize (Zea mays L.) via embryogenic callus infection with Agrobacterium tumefaciens was developed. Calli were co-cultivated with the overnight culture of A. tumefaciens strain LBA4404 harboring the pBI121 plasmid with the nptII and uidA genes. Thereafter, the sensitivity of calli and regenerated plantlets to kanamycin (Km) was determined. It was shown that kanamycin selection was more efficient at the stage of regenerated plantlets than in callus culture. Both vacuum infiltration at the infection step and preliminary activation of Agrobacterium by acetosyringone or by tobacco leaves exudate increased the frequency of Km-resistant plants. The frequency of Km-resistant plants also varied depending on the morphogenic ability of calli. Polymerase chain reaction confirmed the presence of the nptII gene in the genome of regenerated plants and their progeny. β-Glucuronidase gene expression was observed in roots of T1 plants.

Improved Cucumber Transformation by a Modified Explant Dissection and Selection Protocol

Agrobacterium-mediated transformation of Cucumis sativus L. cotyledons was investigated, to identify important factors that affect transformation efficiency. The factors evaluated were initial explant preparation, including preculture, pricking of the explant, inoculation time and co-cultivation regime. We also modified the selection regime, compared to previously published protocols. Our results show that dissecting the proximal half of the cotyledon by a V-shaped cut resulted in a higher transformation rate, compared to two other methods of dissection, as indicated by transient β-glucuronidase gene expression. Selection on 100 mg·L-1 kanamycin resulted in the early development of nontransformed shoots, whereas a gradual increase of kanamycin concentration up to 200 mg·L-1 resulted in the subsequent formation of transgenic shoots on the same medium. The overall transformation frequency in these experiments, expressed as the number of rooted, confirmed transgenic plants per initial number of explants, was 1.7%. The stable integration of T-DNA was confirmed in the primary transformants and their progeny. Abbreviations: ABA = abscisic acid; AdS = adenine sulfate; AS = acetosyringone; BA = 6-benzylaminopurine; GA3 = gibberellic acid; IBA = indolebutyric acid.

Tissue specific expression of β-glucuronidase gene driven by heterologous promoters in transgenic cauliflower plants

In this paper we compare five heterologous promoters fused to β-glucuronidase gene in their influence on localization of GUS activity in cauliflower (Brassica oleracea var. botrytis) tissues: roots, leaves, petioles and curds. A constitutive promoter CaMV 35S and four tissue specific promoters were used: extAP from rape, PsMTAP from pea, RBCS3CP from tomato and SRS1P from soybean, and introduced into cauliflower seedling explants using Agrobacterium rhizogenes mediated transformation. Quantitative and histochemical GUS assays confirmed tissue specific gus expression. It was found that extAP promoter was the most active in petioles but also caused a significant gus expression in curds. GUS activity was hardly observed in curd and restricted only to its epidermis when PsMTAP promoter drove the gene. RBCS3CP and SRS1P promoters controlled similar expression of the gus gene throughout the plant except for curd where RBCS3CP was almost inactive.

Isolation and study of a ubiquitously expressed tomato pectin methylesterase regulatory region

Pectin methylesterase (PME) is an enzyme located in the plant cell wall of higher plants whose physiological role is largely unknown. We had isolated a PME gene from a tomato genomic library, including 2.59 kb of 5´ flanking region and the coding region. Both coding and promoter region were sequenced and computer analyzed. Tobacco transgenic plants were created harboring constructs in which 2.596 Kb, 1.306 Kb and 0.267 Kb sizes of the promoter were driving the expression of β-Glucuronidase gene (GUS). GUS activity was studied by histochemical and fluorometric assays. Two introns of 106 and 1039 bp were found in the coding region and phylogenetic analysis placed this PME gene closer to genes from Citrus sinensis and Arabidopsis thaliana than tomato fruit-specific PME genes. In the promoter, it was found direct repeats, perfect inverted repeats and light responsive elements. GUS histochemical analysis showed activity in all plant tissues with the exception of pollen. The reduction in the promoter size induced a reduction in GUS activity in root, stem and leaf. Furthermore, root and leaf showed the highest and lowest activity, respectively. We had isolated a tomato PME gene with novel characteristics as compared with other known PME genes from tomato.

Population density-dependent regulation of E. coli β-glucuronidase gene expression

Population density-dependent regulation of E. coli β-glucuronidase gene expression

The promoter of the spinach PsaF gene for the subunit III of the photosystem I reaction center directs β-glucuronidase gene expression in transgenic tobacco roots

PsaF is a nuclear encoded gene for the subunit III of photosystem I. It is located at the lumenal side of the thylakoid membrane and interacts with plastocyanin. Starting from a low-level expression in the cotyledons of etiolated seedlings the gene is upregulated by light. Light can be replaced by Ca2+ or phosphoinositides like phorbol myristate acetate, an analogue of diacylglycerol. We tested the effects of these components on PsaF promoter-driven gene expression in roots and found that the PsaF promoter includes a positive regulatory region [-220/-179] activated by cytokinin and a negative regulatory region [-687/-221] activated by abscisic acid. In addition, the promoter is activated by Ca2+, mastoparan and phorbol myristate acetate which suggests a role for phospholipases and protein kinase C in PsaF gene expression.

Culturing shoot-tip clumps of pearl millet [Pennisetum glaucum (L.) R. Br.] and optimal microprojectile bombardment parameters for transient expression

Microprojectile bombardment and transient expression of the reporter gene, β-glucuronidase (GUS) in a novel target tissue, multiple-shoot-tip clumps of pearl millet [Pennisetum glaucum (L.) R. Br.] is reported here. The multiple-shoot-tip clumps were developed in vitro from shoot-apices of seedlings. Using this method, the apical meristems along with the germline cells were easily exposed for bombardment without loss of viability. Further growth of the multiple-shoot-tip clumps was not substantially affected by microprojectile bombardment. Transient expression of β-glucuronidase gene was detected in the form of blue transformed cell sectors in the bombarded tissue by an in situ enzyme assay. The blue sectors were used as convenient criteria to study several factors affecting gene transfer efficiency. Optimal conditions for efficient transient expression of the GUS gene have been defined to aid future strategies of genetic engineering in pearl millet with agronomically important genes.

A wheat group 1 Lea intron enhances β-glucuronidase gene expression in cereal cells

Summary The Group 1 late embryogenesis abundant ( Lea ) genes, typified by the wheat Em gene, are expressed to very high levels during the final third of embryo maturation. The structure of Group 1 Lea genes is highly homologous and all contain one small intron at a conserved location in the coding region. Due to the general correlation between the presence of an intron and enhanced expression, it was of interest to determine if the wheat Em intron contributes to high level expression. The intron from the wheat Em gene was embedded in the NH 2 -terminal region of the β-glucuronidase (GUS) reporter gene coding region such that enzyme activity is dependent on splicing and expression was analyzed in both in vivo and in vitro expression systems. The results show that the Em intron is efficiently spliced (>80%) in transfected rice protoplasts using the normal wheat donor and acceptor sites. However, normalized enzyme activity directed by the intron-containing plasmid is only slightly higher than from an analogous non-intron-containing plasmid. It is further demonstrated that intron-associated enhancement of enzyme activity can be accounted for by differences in spliced GUS mRNA levels and that three novel amino acid codons inserted into the GUS messenger RNA (mRNA) as a result of splicing do not contribute to enhanced expression. We conclude that although this Group 1 Lea intron is able to enhance expression, it does not contribute significantly to high level expression during embryo maturation.

486 Expression of β-glucuronidase Gene in Aspen under Control of CaMV35S, Heat Shock and RolC Promoters

Transgenic hybrid aspens (Populus tremuloides × P. tremula) were produced by Agrobacterium-mediated transformation and confirmed by polymerase chain reaction. Three promoters (CaMV 35S, Heat shock, and Rol C) were used to drive transcription of chimeric genes -glucuronidase (GUS), npt-II, and rol B. Stem sections in ≈100 mm thick, leaf blades, and root tips of transgenic aspen were treated with X-Gluc solution for 2 to 12 h in a 37 °C incubator and fixed in a solution containing 5% formaldehyde, 5% acetic acid, and 20% ethanol (FAA) for 10 min. After washing with 50% ethanol twice and clearing with absolute ethanol until free of chlorophyll, the GUS expression (localization and intensity of blue staining) in leaf, stem, and root at different growth stages were evaluated and photographed under the light microscope. When CaMV35S and rol C were used as promoters, the GUS gene was expressed in all parts of mature stem except pith, with the strongest activity in phloem. The heat shock promoter gave rise to very strong expression only in epidermis and phloem. In the young stem, GUS activity was detected in epidermis, parenchyma, vascular cambium, and primary xylem in CaMV35S-GUS transformed aspen shoots. The rol C promoter produced GUS gene expression in all stem tissues. When the heat shock promoter was used, the GUS gene expressed in a more tissue-specific manner, especially in mature stems, with activity mainly in parenchyma. In young leaf tissues, the GUS activity was primarily located in veins and mesophyll. In the mature leaves, no blue staining was found in the main vein. In root tip, the GUS gene driven by CaMV35S and heat shock promoters were expressed in the columella, vascular, and root apical meristem with very strong expression in the root apical meristem. Aspen plants transformed by rol C-Gus construct showed less or no expression in the columella.

The use of amoxicillin and ticarcillin in combination with a β-lactamase inhibitor as decontaminating agents in the Agrobacterium tumefaciens-mediated transformation of Artemisia annua L.

Artemisinin is a new very promising antimalarial compound produced in the areal parts of the plant Artemisia annua L. (Asteraceae). There is a great interest in the overproduction of artemisinin by means of transgenic plants. The existing Agrobacterium tumefaciens-mediated transformation procedure uses the expensive decontaminating agent vancomycin. In addition vancomycin exhibits a low activity against the Agrobacteria. This paper describes the use of the penicillin derivatives amoxicillin and ticarcillin in combination with the β-lactamase inhibitor clavulanic acid, on the market as Augmentin® and Timentin® (Smith Kline Beecham Pharma S.A., Genval, Belgium), respectively. Sensitivity studies revealed that those antibiotics still permit plant regeneration. The leaf disc transformation was performed with the C58C1 (pGV2260; pTJK136) Agrobacterium strain. Transgenic tissue was selected on 20 mg l −1 kanamycin. The integration of the foreign genes was proven by polymerase chain reactions and additional DNA sequencing. β-Glucuronidase gene expression analyses were performed. In all cases transgenic callus could be obtained, but the shoot regeneration failed. Decontamination was most efficient when high initial concentrations of Augmentin® and Timentin® (300 and 200 mg l −1, respectively) were used. Those concentrations can gradually be reduced. We may conclude that decontamination by the penicillin derived antibiotics is cheaper and more efficient than vancomycin, but is only suitable when the production of callus is desired, for example for the establishment of cell cultures.

Screening for stable transformants and stability of β-glucuronidase gene expression in suspension cultured cells of tall fescue (Festuca arundinacea)

By screening cell colonies derived from protoplasts of tall fescue (Festuca arundinacea), transformed with a rice actin-1-promoter-ß-glucuronidase gene construct, several ß-glucuronidase positive callus clones were obtained. Two callus clones with different GUS expression were derived from these. One was light blue after X-gluc staining, and expression of the ß-glucuronidase gene was stable over repeated subculture, while another stained intensely blue, and expression of the ß-glucuronidase gene was unstable. Southern blot analysis showed that only one copy of the ß-glucuronidase gene was integrated into the genome, and that these two clones appeared to have the same integration pattern. Treatment with 5-azacytidine maintained GUS expression in the unstable line but had no effect on reactivating expression of the GUS gene after expression had been lost. Following the screening procedure the callus clones would only regenerate albino plants.

Microprojectile-mediated DNA delivery to the Salicaceae family

A transient gene expression system was developed for the Salicaceae family using microprojectile-mediated DNA delivery (Biolistic™) to cell suspensions. Using Populus nigra × Populus maximowiczii line NM1, 10 variables were optimized. Optimum transient gene expression under the 10 conditions tested was obtained with a 7- to 9-day-old cell suspension. Highest transient levels were observed with samples positioned 13.5 cm from the stopping plate and bombarded with 1.6-μm gold particles coated with 1 μg of DNA precipitated with CaCl2. Assaying for β-glucuronidase gene expression was performed 1 day after bombardment. The fate of the microparticles in the bombarded cells was studied, showing that 58.9% of cells expressing the β-glucuronidase gene had microparticles located in the nucleus or its vicinity and the remaining cells had microparticles in the cytoplasm. Cell suspensions from five different lines (P. nigra × P. maximowiczii lines NM1 and NM6, Populus deltoides × P. nigra line DN106, Populus tremula × Populus alba line 7171-B4, and Salix alba sanguined line SA-2) yielded transient gene expression. The relative strengths of β-glucuronidase expression in the lines tested were NM1 = 7171-B4 &gt; NM6 &gt; DN106 &gt; SA-2. Six plasmid constructions were also tested in line NM1 for transient β-glucuronidase gene expression. The x-glucuronide histochemical assay did not reveal any differences, but the methyl umbelliferone glucuronide fluorescent assay yielded the following relative levels of transient gene expression with the different promoter sequences: 35S-35S-AMV enhancer = 35S-AMV enhancer &gt; 35S-35S = 35S-35S-AMV enhancer with the β-glucuronidase – neomycin phosphotransferase fusion &gt; 35S. Four transgenic cell lines of P. nigra × P. maximowiczii were characterized for kanamycin resistance and neomycin phosphotransferase II gene activity. Polymerase chain reaction and Southern hybridization analyses indicated the presence of the β-glucuronidase and neomycin phosphotransferase II genes in the genome of three of these transgenic lines. Key words: microprojectile, particle bombardment, Salicaceae, poplar, willow.