Osmotic stress tolerance of transgenic tobacco expressing a gene encoding a membrane-located receptor-like protein from tobacco plants

Tobacco (Nicotiana tabacum) genes regulated during the early stage of responses to wounding were screened by a modified fluorescence differential display method. Among 28 genes initially identified, a particular clone designated NtC7 was subjected to further analysis. Its transcripts were found to accumulate rapidly and transiently within 1 h upon treatments with not only wounding but also salt and osmotic stresses. However, jasmonic and abscisic acids and ethylene did not effectively induce NtC7 transcripts. Amino acid sequence analysis suggested NtC7 to be a new type of transmembrane protein that belongs to the receptor-like protein family, and a membrane location was confirmed in onion (Allium cepa) epidermis cells transiently expressing an NtC7-green fluorescent protein fusion protein. Seeds of transgenic tobacco overexpressing NtC7 normally germinated and grew in the presence of 500 mM mannitol, but not in the presence of 220 mM sodium chloride or 60 mM lithium chloride. Cuttings of mature transgenic leaf exhibited a marked tolerance upon treatment with 500 mM mannitol for 12 h, at which concentration wild-type counterparts were seriously damaged. These results suggested that NtC7 predominantly functions in maintenance of osmotic adjustment independently of ion homeostasis.

Conservation between animals and plants of the cis-acting element involved in the unfolded protein response

Using Arabidopsis thaliana, we identified the cis-element involved in the plant unfolded protein response (UPR). In transgenic plants, tunicamycin stimulated expression of a reporter gene under the control of the BiP promoter and promoter analysis identified a 24 bp sequence crucial to this induction. When fused with a minimal promoter, a hexamer of this sequence was sufficient for induction of a reporter gene in protoplasts treated with tunicamycin or dithiothreitol. Induction rate equivalent to original promoter was observed when the assay was conducted in transgenic plants. This 24 bp sequence contained two elements also responsible for the UPR in animals. Either of these elements was sufficient for the plant UPR, indicating conservation between animals and plants of cis-elements involved in the UPR.

Periodic DNA methylation in maize nucleosomes and demethylation by environmental stress

When maize seedlings were exposed to cold stress, a genome-wide demethylation occurred in root tissues. Screening of genomic DNA identified one particular fragment that was demethylated during chilling. This 1.8-kb fragment, designated ZmMI1, contained part of the coding region of a putative protein and part of a retrotransposon-like sequence. ZmMI1 was transcribed only under cold stress. Direct methylation mapping revealed that hypomethylated regions spanning 150 bases alternated with hypermethylated regions spanning 50 bases. Analysis of nuclear DNA digested with micrococcal nuclease indicated that these regions corresponded to nucleosome cores and linkers, respectively. Cold stress induced severe demethylation in core regions but left linker regions relatively intact. Thus, methylation and demethylation were periodic in nucleosomes. The following biological significance is conceivable. First, because DNA methylation in nucleosomes induces alteration of gene expression by changing chromatin structures, vast demethylation may serve as a common switch for many genes that are simultaneously controlled upon environmental cues. Second, because artificial demethylation induces heritable changes in plant phenotype (Sano, H., Kamada, I., Youssefian, S., Katsumi, M., and Wabilko, H. (1990) Mol. Gen. Genet. 220, 441-447), altered DNA methylation may result in epigenetic inheritance, in which gene expression is modified without changing the nucleotide sequence.

Functional characterization of a heavy metal binding protein CdI19 from Arabidopsis

Heavy metals are potentially highly toxic for organisms. Plants possess the ability to minimize damage but the underlying molecular mechanisms have yet to be detailed. Screening Cd-responsive genes in Arabidopsis, we previously identified a gene encoding a putative metal binding protein CdI19, which, upon introduction into yeast cells, conferred marked toleration of Cd exposure. Here we describe that bacterially expressed CdI19 directly interacts with Cd at its CXXC motif, as revealed by circular dichroism analysis, and that it is exclusively localized at plasma membranes, as revealed by heterologous expression of fusion product with a green fluorescent protein in BY2 cells. Northern blot analyses indicated that CdI19 transcripts were induced not only by Cd, but also by dicationic forms of Hg, Fe and Cu. Histochemical assays using transgenic Arabidopsis expressing the CdI19 promoter::GUS showed CdI19 to be expressed in petiole, hypocotyl, peduncle and vascular bundles in root tissues. Overexpression of the CdI19 cDNA conferred Cd tolerance in transgenic Arabidopsis. These results suggest that CdI19 plays an important role in the maintenance of heavy metal homeostasis and/or in detoxification by endowing plasma membranes with the capacity to serve as an initial barrier against inflow of free heavy metal ions into cells.

Immunosuppressive properties of human amniotic membrane for mixed lymphocyte reaction

The combination of allograft limbal transplantation (ALT) and amniotic membrane transplantation (AMT) has been applied in the treatment of severe ocular surface diseases. The beneficial effect of this combination has been thought to result from possible immunosuppressive ability of amniotic membrane (AM). However, the mechanisms of any such ability remain unknown. In this study, we investigated whether human AM has the ability to suppress allo-reactive T cell responses in vitro. For mixed lymphocyte reaction (MLR), lymphocytes isolated from lymph nodes of C57BL/6 mice (Mls1b, Vbeta6+) were cultured with irradiated splenocytes from DBA/2 mice (Mls1a, Vbeta6-) with or without human AM. For carboxyfluorescein diacetate succinimidyl ester (CFSE) experiments, responder lymph node cells were labelled with a stable intracellular fluorescent dye and cultured with irradiated stimulator cells. The ratio of responder Vbeta6+ T cells was then determined by FACS analysis, and the division profiles of responder Vbeta6+ T cells were analysed by CFSE content. Furthermore, Th1 and Th2 cytokine synthesis by allo-reactive T cells in MLR culture supernatants was determined by enzyme-linked immunosorbent assay (ELISA). Addition of AM to the MLR culture resulted in the significant inhibition of thymidine incorporation compared with control culture lacking AM. The population of responder CD4+Vbeta6+ T cells was significantly reduced in the AM-treated culture in comparison to control. CFSE analysis revealed less division and lower proliferation of responder CD4+Vbeta6+ T cells in cultures with AM than without. In addition, allo-rective T cell synthesis of both Th1 (IL-2 and IFNgamma) and Th2 (IL-6 and IL-10) type cytokine was significantly decreased in the presence of AM. These results indicate that human AM has the ability to suppress allo-reactive T cells in vitro. This inhibitory effect likely contributes to the success of the ALT-AMT combination.

Genomic structure and promoter analysis of phosphoenolpyruvate carboxylase in a C3 plant, Nicotiana sylvestris

Three genes encoding phosphoenolpyruvate carboxylase were isolated from Nicotiana sylvestris and designated Nsppc1-3. Sequencing of nucleotides showed that the coding sequence and deduced amino acid sequences were highly conserved among the genes, but sequences for noncoding regions including introns and 5'-flanking regions were not conserved. Analysis of the transcript level of the genes by a combination of reverse transcriptase-PCR and restriction fragment polymorphism showed mostNsppc1 in the leaves, stems, roots, and cultured cells of N. sylvestris. beta-Glucuronidase activity was detected histochemically in mesophyll cells in leaves, lateral buds, and vascular bundles in roots of transgenic tobacco harboring a chimeric construct of the Nsppc1 promoter and the gene for beta-glucuronidase. Deletion analysis indicated the presence of a silencer-like element for basal expression in the promoter region of Nsppc1.

CAR- or alphav integrin-binding ablated adenovirus vectors, but not fiber-modified vectors containing RGD peptide, do not change the systemic gene transfer properties in mice

Targeted gene delivery to the tissue of interest by recombinant adenovirus (Ad) vectors is limited by the relatively broad expression of the primary receptor, the coxsackievirus and adenovirus receptor (CAR), and the secondary receptor, alphav integrin. This problem could be overcome by mutating the fiber and penton base, which bind with CAR and alphav integrin, respectively. In this study, we constructed CAR-binding ablated Ad vectors and alphav integrin-binding ablated Ad vectors by mutation in the FG loop of fiber knob and in the RGD motif of penton base, respectively, and compared the gene transfer properties of their vectors into various types of cultured cells and mice with conventional Ad vectors. We also generated Ad vectors containing RGD peptide in the HI loop of the fiber knob. CAR-binding ablated Ad vectors mediated about 1% of gene transfer activity into CAR-positive cultured cells, compared with conventional Ad vectors, while alphav integrin-binding ablated Ad vectors maintained at least 76% of gene transfer activity into cultured CAR-positive cells. Inclusion of the RGD peptide into the HI loop of the fiber knob of CAR-binding ablated Ad vectors restored gene transfer activity in vitro. On the other hand, systemically administered CAR-binding ablated Ad vectors, as well as alphav integrin-binding ablated Ad vectors mediated similar levels of gene transfer into mouse liver with the conventional Ad vectors. These results suggest that continued interaction of either the fiber with CAR or the penton base with alphav integrin offers an effective route of virus entry into mouse liver in vivo. Inhibition of the interaction of both the fiber with CAR and the penton base with alphav integrin is likely to be crucial to the development of targeted Ad vectors.

Isolation and characterization of a putative transducer of endoplasmic reticulum stress in Oryza sativa

Following endoplasmic reticulum (ER) stress that prevents correct folding or assembly of ER proteins, at least three responses occur to maintain cell homeostasis: induction of chaperones, attenuation of protein synthesis, and enhancement of lipid synthesis. Transducers that transmit ER stress to the nucleus have already been identified in yeast and mammals. We report here isolation of a cDNA, OsIre1, from rice encoding a putative homolog of Ire1p, a yeast transducer of ER stress. OsIre1 encodes a polypeptide consisting of 893 amino acids, in which two hydrophobic stretches are present in the amino-terminal (N-terminal) and middle regions, possibly serving as a signal peptide and a transmembrane domain, respectively. The carboxyl-terminal (C-terminal) domain was found to possess serine/threonine protein kinase and ribonuclease-like domains showing high similarities with regions in Ire1 homologs from other organisms. A fusion protein of OsIre1 and green fluorescent protein (GFP) expressed in tobacco BY2 cells could be demonstrated to localize to the ER and the N-terminal domain of OsIre1 could substitute for yeast Ire1p in yeast cells. When produced in bacteria as a fusion protein, the C-terminal region of OsIre1 showed autophosphorylation activity. These results thus indicate that OsIre1 encodes a putative plant transducer of ER stress.

Diminished inibitory action of ethanol on the contraction of gallbladder isolated from chronically ethanol-fed Guinea pigs

Ethanol is known to decrease the gallbladder contractility. The purpose of this study was to clarify the mechanism of tolerance to the inhibitory action of ethanol on the gallbladder contractility. Male guinea pigs were fed ethanol (3%) or calorie-matched sucrose in the drinking water for 4 weeks. Then, the gallbladder was isolated, and its isometric tension was measured. The contractile responses to KCl, BAY K8644, histamine, and phorbol 12,13-dibutyrate in the normal medium were not different between the gallbladder strips from ethanol-fed and control guinea pigs. Ethanol at 25 mmol/l in vitro did not affect the contractile responses to KCl and BAY K8644 in the gallbladder strips from both ethanol-fed and control guinea pigs. On the other hand, ethanol at 25 mmol/l in vitro significantly inhibited the contractile responses to histamine and phorbol 12,13-dibutyrate in the gallbladder strips from the control guinea pigs, but it did not affect the contractile response to histamine and significantly augmented that to phorbol 12,13-dibutyrate in the strips from the ethanol-fed guinea pigs. Diphenhydramine, a selective H(1) receptor antagonist, abolished the histamine contraction in gallbladder strips from both control and ethanol-fed guinea pigs, while cimetidine, a selective H(2) receptor antagonist, did not affect histamine contraction, implying that histamine-induced contraction of guinea pig gallbladders is mediated only by H(1) receptors. Verapamil (1 micromol/l) completely inhibited the phorbol 12,13-dibutyrate-induced contraction of the strips from both ethanol-fed and control guinea pigs. The histamine-induced contraction was partly inhibited in the absence of Ca(2+) in the medium. In the gallbladder strips from both ethanol-fed and control guinea pigs, ethanol at 25 mmol/ in vitro did not affect the histamine-induced contraction in the absence of extracellular Ca(2+). Tolerance to the inhibitory action of ethanol developed selectively on contractile responses to histamine and phorbol 12,13-dibutyrate. Chronic ethanol administration produces tolerance to in vitro gallbladder contractility mediated by the Ca(2+) entry through L-type Ca(2+) channels linked with protein kinase C activation.

A chloroplast-resident DNA methyltransferase is responsible for hypermethylation of chloroplast genes in Chlamydomonas maternal gametes

Chloroplast DNA of the green alga Chlamydomonas reinhardtii is maternally inherited. Methylation mapping directly revealed that, before mating, chloroplast DNA of maternal (mating type plus; mt(+)) gametes is heavily methylated whereas that of paternal (mating type minus; mt(-)) gametes is not. Indirect immunofluorescence analyses with anti-5-methylcytosine mAbs visually showed methylation to occur exclusively in chloroplast DNA of mt(+) gametes, and not in mt(-) gametes or nuclear DNA of either mt. To clarify the relationship between methylation and maternal inheritance of chloroplast DNA, we have isolated and characterized a cDNA encoding a DNA methyltransferase. The deduced protein, CrMET1, consists of 1,344 aa and contains a conserved catalytic domain at the C terminal and a nonconserved N-terminal region. The predicted N-terminal region has an arginine-rich domain, suggesting CrMET1 is transferred to chloroplasts. This finding could be directly shown by green fluorescent protein epifluorescence microscopy analyses. CrMET1 transcripts were found to be absent in both mt(+) and mt(-) vegetative cells. Upon gametogenesis, however, transcript levels clearly increased in mt(+) but not mt(-) cells. These experiments suggest that the CrMET1 protein is located in chloroplasts and that it specifically methylates cytosine residues of chloroplast DNA in mt(+) gametes. This conclusion was further strengthened by the observation that, during gametogenesis, CrMET1 is expressed in a mt(-) mutant, mat-1, whose chloroplast DNA is heavily methylated in gametes and paternally inherited. The results provide evidence that cytosine methylation plays a critical role in maternal inheritance of chloroplast genes in C. reinhardtii.

Identification of early-responsive genes associated with the hypersensitive response to tobacco mosaic virus and characterization of a WRKY-type transcription factor in tobacco plants

In order to identify genes that are involved in the defense reaction against pathogen attack, we screened for examples that are regulated during the hypersensitive response (HR) to infection by tobacco mosaic virus (TMV) of tobacco ( Nicotiana tabacum cv. Xanthi nc) carrying the N gene, which confers resistance to TMV. Among seven genes initially identified by fluorescent differential display, one clone was further characterized because its transcripts accumulated rapidly and transiently after the onset of HR. Its full-length cDNA of 1346 bp encoded a polypeptide consisting of 258 amino acids. The deduced protein contained a single WRKY domain, a Cys(2)His(2) zinc-finger motif and a leucine-zipper motif, showing high similarity to WIZZ, a member of the family of WRKY transcription factors in tobacco. The gene was thus designated TIZZ. A GFP-TIZZ fusion protein was found to localize to the nucleus upon introduction into epidermal cells of onion. Bacterially expressed TIZZ was able to bind to the W-box (TTGAC) element that is recognized by other WRKY proteins, but transactivation assays showed it to be unable to activate reporter gene expression by itself. TIZZ transcripts were induced in TMV-infected nahG transgenic tobacco plants, in which salicylic acid fails to accumulate. Neither exogenously applied salicylic acid nor mechanical wounding induced TIZZ transcript accumulation. These results indicate the presence of salicylic acid-independent pathways for HR signal transduction, in which a novel type of WRKY protein(s) may play a critical role for the activation of defense.

flaB-polymerase chain reaction (flaB-PCR) and its restriction fragment length polymorphism (RFLP) analysis are an efficient tool for detection and identification of Leptospira spp

For establishment of a rapid-identification method of Leptospira species, a flaB gene of Leptospira was investigated and the following results were obtained. 1) HaeIII- or HindIII-restriction fragment length polymorphism (RFLP) of polymerase chain reaction (PCR) products (793 bp) of flaB gene was effectual for the classification of species of Leptospira. 2) Twenty cells of Leptospira in 1 ml of coagulated blood and 100 cells of Leptospira in 1 ml of anti-coagulated blood could be detected by flaB-PCR. These results suggested that PCR-RFLP based on the flaB gene was an efficient tool for rapid detection and identification of species of infected Leptospira from clinical specimens.

[A case of leptospirosis infected in Borneo Island, Malaysia]

We report a case of leptospirosis infected in Sabah, Borneo island, Malaysia. The case is 25-year-old male who had participated in the EcoChallenge Sabah 2000 Expedition Race, a multisport event held during August 20 to September 3, 2000 at various sites in Sabah in Malaysian Borneo. He developed a high fever and headache on September 7, and he was admitted to our hospital on September 9. On admission he also had conjunctivitis and myalgias. Laboratory findings on admission revealed leukocytosis with left shift, slightly elevated transaminase levels, high CRP levels and proteinuria. Plasmodium spp. were negative on blood smears, and no bacteria were isolated from blood and feces cultures. We performed the laboratory tests for leptospirosis, based on the information about the probable leptospirosis outbreak among athletes who participated in the EcoChallenge Race, however both Leptospira antigens and antibodies were negative at that time. We diagnosed leptospirosis clinically because he manifested persistent symptoms, and minocycline 100 mg b.i.d. was administered intravenously resulting in excellent efficacy. Serum antibody tests by microscopic agglutination test (MAT) at convalescent stage revealed significant increased antibodies against Leptospira interrogans serovar hebdomadis, and the diagnosis of leptospirosis was confirmed. Infectious diseases have been global and it is important to have information concerning worldwide infectious disease situations as much as possible for accurate diagnosis.

Efficient gene transfer by fiber-mutant adenoviral vectors containing RGD peptide

One of the hurdles to adenovirus (Ad)-mediated gene transfer is that Ad vectors mediate inefficient gene transfer into cells lacking in the primary receptors, Coxsackievirus and adenovirus receptor (CAR). We previously developed a fiber-mutant Ad vector containing the Arg-Gly-Asp (RGD)-containing peptide motif on the HI loop of the fiber knob, and showed that the mutant vector had enhanced gene transfer activity to human glioma cells, which showed little CAR expression, compared to the vector containing wild type fiber. In this study, the feasibility of the Ad vector containing RGD peptide on the fiber knob was examined in a wide variety of cell types: CAR-positive or -negative human tumor cells, mouse cells, and leukemia cells. The mutant vector infected the cells, which lacked CAR expression but showed alpha(v) integrin expression, about 10-1000 times more efficiently than the vector containing wild type fiber via an RGD-integrin (alpha(v)beta3 and alpha(v)beta5)-dependent, CAR-independent cell entry pathway. The results of this study indicate that Ad vector containing RGD peptide on the fiber knob could be of great utility for gene therapy and gene transfer experiments.

Molecular characterization of two Arabidopsis Ire1 homologs, endoplasmic reticulum-located transmembrane protein kinases

A major response of eukaryotic cells to the presence of unfolded proteins in the lumen of the endoplasmic reticulum (ER) is to activate genes that encode ER-located molecular chaperones, such as the binding protein. This response, called the unfolded protein response, requires the transduction of a signal from the ER to the nucleus. In yeast (Saccharomyces cerevisiae) and mammalian cells, an ER-located transmembrane receptor protein kinase/ribonuclease called Ire1, with a sensor domain in the lumen of the ER, is the first component of this pathway. Here, we report the cloning and derived amino acid sequences of AtIre1-1 and AtIre1-2, two Arabidopsis homologs of Ire1. The two proteins are located in the perinuclear ER (based on heterologous expression of fusions with green fluorescent protein). The expression patterns of the two genes (using beta-glucuronidase fusions) are nearly nonoverlapping. We also demonstrate functional complementation of the sensor domains of the two proteins in yeast and show that the Ire1-2 protein is capable of autotransphosphorylation. These and other findings are discussed in relation to the involvement of these genes in unfolded protein response signaling in plants.

Cultivated corneal epithelial stem cell transplantation in ocular surface disorders

PURPOSE

To investigate the outcome of cultivated corneal epithelial transplantation for severe stem cell deficiencies using denuded amniotic membrane (AM) as a carrier.

DESIGN

Retrospective, noncomparative case series.

PARTICIPANTS

Thirteen eyes of 11 patients were studied. These consisted of five eyes with acute Stevens-Johnson syndrome (SJS), two with chronic SJS, one with an acute chemical injury, two with chronic chemical injuries, two with ocular cicatricial pemphigoid, and one with drug-induced pseudopemphigoid. All of these eyes had total stem cell deficiencies.

MAIN OUTCOME MEASURES

Adaptation of the cultivated corneal epithelium onto the host corneal surface was confirmed 48 hours after surgery. The reconstruction of the ocular surface and visual acuity were measured.

METHODS

Corneal limbal epithelium from donor corneas was cultivated for 4 weeks on a denuded AM carrier, with 3T3 fibroblast coculture and air lifting. The cultivated corneal epithelium showed four to five layers of stratification and was well differentiated. After conjunctival tissue removal from the cornea up to 3 mm outside the limbus and subconjunctival tissue treatment with 0.04% mitomycin C, cultivated allocorneal epithelium, including the AM carrier, was transplanted onto the corneal surface up to the limbus. Lamellar keratoplasty, using preserved donor graft without epithelium, was performed simultaneously for five chronic-phase patients showing corneal stromal scarring. Systemic immunosuppression was used to prevent allograft rejection.

RESULTS

In all 13 eyes, the entire corneal surface, on which cultivated allocorneal epithelium had been placed, was free from epithelial defects 48 hours after surgery, indicating complete survival of the transplanted corneal epithelium. Visual acuity improved in all eyes after surgery, and 10 of the 13 eyes were restored to good vision (postoperative visual acuity improved two or more lines) 6 months after the operation. During the follow-up period (mean +/- standard deviation, 11.2 +/- 1.3 months), the corneal surfaces were clear, although three eyes experienced epithelial rejection.

CONCLUSIONS

Cultivated corneal epithelial transplantation using denuded AM as a carrier can be used for severe stem cell deficiencies.

An Arabidopsis SNF1-related protein kinase, AtSR1, interacts with a calcium-binding protein, AtCBL2, of which transcripts respond to light

AtSR1 is a protein kinase of Arabidopsis thaliana, which belongs to the SNF1-related protein kinase subfamily 3. We previously showed accumulation of its transcripts to be responsive to light. In this study, we examined the interaction between AtSR1 and six calcineurin B like proteins of Arabidopsis and found that AtSR1 prominently interacts with one of them, AtCBL2, by yeast two-hybrid assay. Interaction between AtSR1 and AtCBL2 could also be directly confirmed in vitro by pull down assay. RNA blot and reverse transcription-polymerase chain reaction analyses showed that transcripts of AtCBL2, and also of AtCBL1, another CBL, increased upon illumination of leaves. The physiological meaning of the interaction of AtSR1and AtCBL2 is not clear, but they presumably function in signal transduction of light.

A simplified system for constructing recombinant adenoviral vectors containing heterologous peptides in the HI loop of their fiber knob

The use of recombinant adenovirus (Ad) vectors containing genetically modified capsid proteins is an attractive strategy for achieving targeted gene transfer. The HI loop of the fiber knob is a promising candidate location for the incorporation of foreign ligands for achieving this goal. However, the method of constructing an Ad vector containing a foreign ligand in the HI loop of the fiber knob has proved difficult. In this study, we developed a simple system to construct fiber-modified vectors. To do this, a vector plasmid containing a complete E1/E3-deleted Ad type 5 genome and a unique Csp45I and/or ClaI site between positions 32679 and 32680 of the Ad genome (residues threonine-546 and proline-547 of the fiber protein) was constructed. Oligonucleotides corresponding to the Arg-Gly-Asp (RGD) or Asn-Gly-Arg (NGR)-containing peptide motif (as a model) and containing a Csp45I and/or ClaI recognition site, were ligated into the Csp45I and/or ClaI-digested plasmid. The foreign transgene expression cassette was inserted into the E1 deletion site of the vector plasmid and the fiber-mutant Ad vector was produced by transfection of the PacI-digested plasmid into 293 cells. The virus containing the RGD or NGR peptide on the fiber knob was able to infect human glioma cells, which do not express coxsackievirus and adenovirus receptor (CAR), one of the Ad virus receptors, about 100-1000 times more efficient than the virus containing wild-type fiber. This suggested that the mutant virus mediated CAR-independent cell entry pathway. The simplicity of this method allows not only for easy construction of fiber-mutant Ad vectors, but also for screening of the peptides that target the vector to the desired cells and tissues.