Overexpressing plant ferredoxin-like protein enhances photosynthetic efficiency and carbohydrates accumulation in Phalaenopsis

Crassulacean acid metabolism (CAM) is one of three major models of carbon dioxide assimilation pathway with better water-use efficiency and slower photosynthetic efficiency in photosynthesis. Previous studies indicated that the gene of sweet pepper plant ferredoxin-like protein (PFLP) shows high homology to the ferredoxin-1(Fd-1) family that belongs to photosynthetic type Fd and involves in photosystem I. It is speculated that overexpressing pflp in the transgenic plant may enhance photosynthetic efficiency through the electron transport chain (ETC). To reveal the function of PFLP in photosynthetic efficiency, pflp transgenic Phalaenopsis, a CAM plant, was generated to analyze photosynthetic markers. Transgenic plants exhibited 1.2-folds of electron transport rate than that of wild type (WT), and higher CO2 assimilation rates up to 1.6 and 1.5-folds samples at 4 pm and 10 pm respectively. Enzyme activity of phosphoenolpyruvate carboxylase (PEPC) was increased to 5.9-folds in Phase III, and NAD+-linked malic enzyme (NAD+-ME) activity increased 1.4-folds in Phase IV in transgenic plants. The photosynthesis products were analyzed between transgenic plants and WT. Soluble sugars contents such as glucose, fructose, and sucrose were found to significantly increase to 1.2, 1.8, and 1.3-folds higher in transgenic plants. The starch grains were also accumulated up to 1.4-folds in transgenic plants than that of WT. These results indicated that overexpressing pflp in transgenic plants increases carbohydrates accumulation by enhancing electron transport flow during photosynthesis. This is the first evidence for the PFLP function in CAM plants. Taken altogether, we suggest that pflp is an applicable gene for agriculture application that enhances electron transport chain efficiency during photosynthesis.

Overexpression of plant ferredoxin-like protein promotes salinity tolerance in rice (Oryza sativa)

High-salinity stress is one of the major limiting factors on crop productivity. Physiological strategies against high-salinity stress include generation of reactive oxygen species (ROS), induction of stress-related genes expression, accumulation of abscisic acid (ABA) and up-regulation of antiporters. ROS are metabolism by-products and involved in signal transduction pathway. Constitutive expression of plant ferrodoxin-like protein (PFLP) gene enhances pathogen-resistance activities and root-hair growth through promoting ROS generation. However, the function of PFLP in abiotic stress responses is unclear. In this study, PFLP-1 and PFLP-2-transgenic rice plants were generated to elucidate the role of PFLP under salinity stress. PFLP overexpression significantly increased salt tolerance in PFLP-transgenic rice plants compared with non-transgenic plants (Oryza sativa japonica cv. Tainung 67, designated as TNG67). In high-salinity conditions, PFLP-transgenic plants exhibited earlier ROS production, higher antioxidant enzyme activities, higher ABA accumulation, up-regulated expression of stress-related genes (OsRBOHa, Cu/Zn SOD, OsAPX, OsNCED2, OsSOS1, OsCIPK24, OsCBL4, and OsNHX2), and leaf sodium ion content was lower compared with TNG67 plant. In addition, transgenic lines maintained electron transport rates and contained lower malondialdhyde (MDA) content than TNG67 plant did under salt-stress conditions. Overall results indicated salinity tolerance was improved by PFLP overexpression in transgenic rice plant. The PFLP gene is a potential candidate for improving salinity tolerance for valuable agricultural crops.

Constitutive expression of a plant ferredoxin-like protein (pflp) enhances capacity of photosynthetic carbon assimilation in rice (Oryza sativa)

The plant ferredoxin-like protein (PFLP) gene, cloned from sweet peppers predicted as an electron carrier in photosynthesis, shows high homology to the Fd-I sequence of Arabidopsis thaliana, Lycopersicon esculentum, Oryza sativa and Spinacia oleracea. Most of pflp related studies focused on anti-pathogenic effects, while less understanding for the effects in photosynthesis with physiological aspects, such as photosynthesis rate, and levels of carbohydrate metabolites. This project focuses on the effects of pflp overexpression on photosynthesis by physiological evaluations of carbon assimilation with significant higher levels of carbohydrates with higher photosynthesis efficiency. In this report, two independent transgenic lines of rice plants (designated as pflp-1 and pflp-2) were generated from non-transgenic TNG67 rice plant (WT). Both transgenic pflp rice plants exhibited enhanced photosynthesis efficiency, and gas exchange rates of photosynthesis were 1.3- and 1.2-fold higher for pflp-1 and pflp-2 than WT respectively. Significantly higher electron transport rates of pflp rice plants were observed. Moreover, photosynthetic products, such as fructose, glucose, sucrose and starch contents of pflp transgenic lines were increased accordingly. Molecular evidences of carbohydrate metabolism related genes activities (osHXK5, osHXK6, osAGPL3, osAGPS2α, osSPS, ospFBPase, oscFBPase, and osSBPase) in transgenic lines were higher than those of WT. For performance of crop production, 1000-grain weight for pflp-1 and pflp-2 rice plants were 52.9 and 41.1 g that were both significantly higher than 31.6 g for WT, and panicles weights were 1.4- and 1.2-fold higher than WT. Panicle number, tiller number per plants for pflp rice plants were all significantly higher compared with those of WT where there was no significant difference observed between two pflp rice plants. Taken altogether; this study demonstrated that constitutive pflp expression can improve rice production by enhancing the capacity of photosynthetic carbon assimilation.

Expression of plant ferredoxin-like protein (PFLP) enhances tolerance to heat stress in Arabidopsis thaliana

Under adverse environments, plants produce reactive oxygen species (ROS), which can trigger cell death when their accumulation surpasses the antioxidant capacity of ROS scavenging systems. These systems function in chloroplasts mainly through the ascorbate-mediated water-water cycle, in which ascorbate is photoreduced by ferredoxin in the photosynthetic system. Our previous study showed that the fraction of the reduced form of ascorbate was increased in ferredoxin-transgenic Arabidopsis (CPF) plants which overexpressed plant ferredoxin-like protein (PFLP) in their chloroplasts. Thus, we hypothesized that expression of PFLP could alter the tolerance of plants to abiotic stresses through increasing reduced form of ascorbate. In this study, we found that two CPF lines exhibited lower mortality rates at five days, following two days of heat treatment. Compared to non-transgenic wild type (Col-0) plants, CPF plants exhibited decreased H2O2 content, MDA accumulation, and ion leakage after heat treatment. To confirm the efficacy of ferredoxin against heat stress in chloroplasts, we evaluated two RNA interference (RNAi) lines on two endogenous ferredoxin isoforms, Atfd1 or Atfd2, of Arabidopsis plants. Both lines not only decreased their amounts of ascorbate, but also exhibited adverse reactions following heat treatment. Based on these results, we conclude that expression of PFLP in chloroplasts can confer tolerance to heat stress. This tolerance might be associated with the increasing of ascorbate in plants.

Ectopically expressed sweet pepper ferredoxin PFLP enhances disease resistance to Pectobacterium carotovorum subsp. carotovorum affected by harpin and protease-mediated hypersensitive response in Arabidopsis

Plant ferredoxin-like protein (PFLP) is a photosynthesis-type ferredoxin (Fd) found in sweet pepper. It contains an iron-sulphur cluster that receives and delivers electrons between enzymes involved in many fundamental metabolic processes. It has been demonstrated that transgenic plants overexpressing PFLP show a high resistance to many bacterial pathogens, although the mechanism remains unclear. In this investigation, the PFLP gene was transferred into Arabidopsis and its defective derivatives, such as npr1 (nonexpresser of pathogenesis-related gene 1) and eds1 (enhanced disease susceptibility 1) mutants and NAHG-transgenic plants. These transgenic plants were then infected with the soft-rot bacterial pathogen Pectobacterium carotovorum subsp. carotovorum (Erwinia carotovora ssp. carotovora, ECC) to investigate the mechanism behind PFLP-mediated resistance. The results revealed that, instead of showing soft-rot symptoms, ECC activated hypersensitive response (HR)-associated events, such as the accumulation of hydrogen peroxide (H2 O2 ), electrical conductivity leakage and expression of the HR marker genes (ATHSR2 and ATHSR3) in PFLP-transgenic Arabidopsis. This PFLP-mediated resistance could be abolished by inhibitors, such as diphenylene iodonium (DPI), 1-l-trans-epoxysuccinyl-leucylamido-(4-guanidino)-butane (E64) and benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone (z-VAD-fmk), but not by myriocin and fumonisin. The PFLP-transgenic plants were resistant to ECC, but not to its harpin mutant strain ECCAC5082. In the npr1 mutant and NAHG-transgenic Arabidopsis, but not in the eds1 mutant, overexpression of the PFLP gene increased resistance to ECC. Based on these results, we suggest that transgenic Arabidopsis contains high levels of ectopic PFLP; this may lead to the recognition of the harpin and to the activation of the HR and other resistance mechanisms, and is dependent on the protease-mediated pathway.

C-terminal region of plant ferredoxin-like protein is required to enhance resistance to bacterial disease in Arabidopsis thaliana

Protein phosphorylation is an important biological process associated with elicitor-induced defense responses in plants. In a previous report, we described how plant ferredoxin-like protein (PFLP) in transgenic plants enhances resistance to bacterial pathogens associated with the hypersensitive response (HR). PFLP possesses a putative casein kinase II phosphorylation (CK2P) site at the C-terminal in which phosphorylation occurs rapidly during defense response. However, the contribution of this site to the enhancement of disease resistance and the intensity of HR has not been clearly demonstrated. In this study, we generated two versions of truncated PFLP, PEC (extant CK2P site) and PDC (deleted CK2P site), and assessed their ability to trigger HR through harpin (HrpZ) derived from Pseudomonas syringae as well as their resistance to Ralstonia solanacearum. In an infiltration assay of HrpZ, PEC intensified harpin-mediated HR; however, PDC negated this effect. Transgenic plants expressing these versions indicate that nonphosphorylated PFLP loses its ability to induce HR or enhance disease resistance against R. solanacearum. Interestingly, the CK2P site of PFLP is required to induce the expression of the NADPH oxidase gene, AtrbohD, which is a reactive oxygen species producing enzyme. This was further confirmed by evaluating the HR on NADPH oxidase in mutants of Arabidopsis. As a result, we have concluded that the CK2P site is required for the phosphorylation of PFLP to enhance disease resistance.

Ectopic ferredoxin I protein promotes root hair growth through induction of reactive oxygen species in Arabidopsis thaliana

Ferredoxin I (Fd-1) is a protein existing in green tissues as an electron carrier for photosynthesis. Reactive oxygen species (ROS) are generated from an over-accumulation of electrons in photosynthetic electron chains. In previous studies, plant ferredoxin-like protein (PFLP) transgenic plants could be made resistant to virulent pathogens, by inducing the generation of ROS. The generation of ROS is closely associated with root hair development, increasing with the elongation of root hairs. We propose that an ectopic expression of pflp may alter root hair development through the enhanced generation of ROS. In this report, Arabidopsis transformed with pflp was generated to determine the potential role of PFLP in root development. Transgenic Arabidopsis exhibited longer root hairs with a significant increase in endogenous H(2)O(2) compared with wild type. The growth of transgenic lines in root hairs was inhibited when treated with NADPH oxidase inhibitor. Results suggest that an over-expression of pflp had enhanced the accumulation of H(2)O(2) in the roots and further promoted the growth of root hairs. Transcriptional activities of root hair development-related and redox-regulated genes were mediated through increased levels of ROS, to alter the growth of transgenic lines in root hairs. In summary, we propose that an ectopic expression of pflp promotes root hair growth, resulting from an enhancement of ROS production.

Plant ferredoxin-like protein (PFLP) outside chloroplast in Arabidopsis enhances disease resistance against bacterial pathogens

Protection of crops against bacterial disease is an important issue in agricultural production. One of the strategies to lead plants become resistant against bacterial pathogens is employing a transgene, like plant ferredoxin-like protein (PFLP). PFLP is a photosynthetic type ferredoxin isolated from sweet pepper and contains a signal peptide for targeting towards chloroplasts. Our previous reports indicated that transgenic plants with this protein are more resistant against bacterial pathogens. However, this heterologous protein was visualized not only inside the chloroplasts, but also in the cytoplasm. In this article, we moved to study its heterologous expression in Arabidopsis by expressing the protein in chloroplast, apoplast and cytoplasm. This work was achieved by engineering a chloroplast target (CPF), an apoplast target (ESF), and cytoplasm target (DF) plants. The expression and subcellular localization of PFLP were analyzed by Western blot and immuno-staining by confocal microscopy, respectively. We tested the ability of the transgenic Arabidopsis for resistance to two Ralstonia solanacearum strains and their ability to increase the hypersensitive response (HR) triggered by harpin (HrpZ) from Pseudomonas syringae. The DF and ESF plants conferred resistance against bacterial wilt strains and increased HR by harpin, but no resistance found in the CPF plants. In addition, we determined the level of reduced ascorbate in all transgenic plants and further analyzed the expression of two NADPH-oxidase genes (AtrbohD and AtrbohF) in ESF plant. Among the transgenic Arabidopsis plants, ESF plants confer the highest resistance to bacterial pathogens and followed by DF plants. We concluded that PFLP enhances disease resistance in Arabidopsis when expressed in the apoplast or in cytoplasm but not when targeted into the chloroplast. This study provides a strategy for molecular breeding to improve resistance of crops against bacterial pathogens.

Retinol-binding protein 4 is associated with impaired glucose regulation and microalbuminuria in a Chinese population

AIMS/HYPOTHESIS

Increased retinol-binding protein 4 (RBP4) has been reported in association with insulin resistance and type 2 diabetes. We aimed to investigate the association of serum RBP4 with impaired glucose regulation and microalbuminuria in Chinese adults aged 40 years or older.

METHODS

Serum RBP4 was measured in 763 individuals with normal glucose regulation, 508 with impaired glucose regulation and 524 newly diagnosed diabetic patients. Serum RBP4 was measured using ELISA and urine albumin/creatinine ratio was used to determine the urinary albumin excretion.

RESULTS

Serum RBP4 concentrations were significantly higher in participants with isolated impaired fasting glucose, isolated impaired glucose tolerance, combined impaired fasting glucose/impaired glucose tolerance and diabetes than in those with normal glucose regulation, whereas serum RBP4 levels were not different in the four groups with dysregulation of glucose metabolism. RBP4 was associated with a higher risk for impaired glucose regulation (OR 1.011 for each 1 microg/ml increase in RBP4, 95% CI 1.000-1.022, p = 0.04) after adjustment for sex, age, BMI, current smoking and alcohol intake, family history of diabetes, insulin resistance, triacylglycerol, total cholesterol, and HDL- and LDL-cholesterol; the corresponding OR of combined impaired glucose regulation and type 2 diabetes was 1.022 (95% CI 1.009-1.035, p = 0.0009). RBP4 was associated with the risk of microalbuminuria (OR 1.023, 95% CI 1.004-1.042, p = 0.01) after adjustment for sex, age, smoking habit and alcohol intake, BMI, waist/hip ratio, homeostasis model assessment of insulin resistance, GFR, triacylglycerol, total cholesterol, and HDL- and LDL-cholesterol.

CONCLUSIONS/INTERPRETATION

Serum RBP4 level is closely associated with impaired glucose regulation and is an independent risk factor for microalbuminuria.

Resistance enhancement of transgenic tomato to bacterial pathogens by the heterologous expression of sweet pepper ferredoxin-I protein

ABSTRACT Expression of a foreign gene to enhance plant disease resistance to bacterial pathogens is a favorable strategy. It has been demonstrated that expressing sweet pepper ferredoxin-I protein (PFLP) in transgenic plants can enhance disease resistance to bacterial pathogens that infect leaf tissue. In this study, PFLP was applied to protect tomato (Lycopersicon esculentum cv. cherry Cln1558a) from the root-infecting pathogen, Ralstonia solanacearum. Independent R. solanacearum resistant T(1) lines were selected and bred to produce homozygous T(2) generations. Selected T(2) transgenic lines 24-18-7 and 26-2-1a, which showed high expression levels of PFLP in root tissue, were resistant to disease caused by R. solanacearum. In contrast, the transgenic line 23-17-1b and nontransgenic tomato, which showed low expression levels of PFLP in root tissue, were not resistant to R. solanacearum infection. The expansion of R. solanacearum populations in stem tissue of transgenic tomato line 24-18-7 was limited compared with the nontransgenic tomato Cln1558a. Using a detached leaf assay, transgenic line 24-18-7 was also resistant to maceration caused by E. carotovora subsp. carotovora; however, resistance to E. carotovora subsp. carotovora was less apparent in transgenic lines 26-2-1a and 23-17-1b. These results demonstrate that PFLP is able to enhance disease resistance at different levels to bacterial pathogens in individual tissue of transgenic tomato.

Production of soft rot resistant calla lily by expressing a ferredoxin-like protein gene (pflp) in transgenic plants

An efficient protocol for the Agrobacterium tumefaciens-mediated transformation of calla lily (Zantedeschia elliottiana (W. Wats.) Engl. cultivar 'Florex Gold') is described. Shoot basal discs were co-cultivated with A. tumefaciens C58C1 carrying a plasmid containing neomycin phosphotransferase (nptII) and plant ferredoxin-like protein (pflp) genes. After Agrobacterium co-cultivation, the shoot basal discs were exposed to 100 mg l(-1) kanamycin for selection. Twenty-eight out of 260 discs (10.8%) were found to have survived and produced shoot clusters. Twenty-six of these were confirmed to contain the pflp transgene by PCR, ending up in 10% transformation efficiency. The disease resistance investigation revealed that 18 transgenic plants exhibited resistance to soft rot disease caused by Erwinia carotovora subsp. carotovora. The presence of pflp gene was demonstrated by PCR, and its accumulation and activity was confirmed by Western blot and disease resistance assay. This was the first report to show the successful transformation and resistance to a bacterial pathogen in Zantedeschia. The protocol is useful for the quality improvement of calla lily through genetic transformation.

Disease resistance to bacterial pathogens affected by the amount of ferredoxin-I protein in plants

SUMMARY Ferredoxin-I (Fd-I) is a fundamental protein that is involved in several metabolic pathways. The amount of Fd-I found in plants is generally regulated by environmental stress, including biotic and abiotic events. In this study, the correlation between quantity of Fd-I and plant disease resistance was investigated. Fd-I levels were increased by inoculation with Pseudomonas syringae pv. syringae but were reduced by Erwinia carotovora ssp. carotovora. Transgenic tobacco over-expressing Fd-I with the sense sweet pepper Fd-I gene (pflp) was resistant to E. carotovora ssp. carotovora and the saprophytic bacterium P. fluorescens. By contrast, transgenic tobacco with reduced total Fd-I and the antisense pflp gene was susceptible to E. carotovora ssp. carotovora and P. fluorescens. Both of these transgenic tobaccos were resistant to P. syringae pv. syringae. By contrast, the mutated E. carotovora ssp. carotovora, with a defective harpin protein, was able to invade the sense-pflp transgenic tobacco as well as the non-transgenic tobacco. An in vitro kinase assay revealed that harpin could activate unidentified kinases to phosphorylate PFLP. These results demonstrate that Fd-I plays an important role in the disease defence mechanism.

Expression of the hypersensitive response-assisting protein in Arabidopsis results in harpin-dependent hypersensitive cell death in response to Erwinia carotovora

Active defense mechanisms of plants against pathogens often include a rapid plant cell death known as the hypersensitive cell death (HCD). Hypersensitive response-assisting protein (HRAP) isolated from sweet pepper intensifies the harpin(Pss)-mediated HCD. Here we demonstrate that constitutive expression of the hrap gene in Arabidopsis results in an enhanced disease resistance towards soft rot pathogen, E. carotovora subsp. carotovora. This resistance was due to the induction of HCD since different HCD markers viz. Athsr3, Athsr4, ion leakage, H(2)O(2) and protein kinase were induced. One of the elicitor harpin proteins, HrpN, from Erwinia carotovora subsp. carotovora was able to induce a stronger HCD in hrap-Arabidopsis than non-transgenic controls. To elucidate the role of HrpN, we used E. carotovora subsp. carotovora defective in HrpN production. The hrpN(-) mutant did not induce disease resistance or HCD markers in hrap-Arabidopsis. These results imply that the disease resistance of hrap-Arabidopsis against a virulent pathogen is harpin dependent.

The sweet pepper ferredoxin-like protein (pflp) conferred resistance against soft rot disease in Oncidium orchid

Genetic engineering to date has not been used to introduce disease resistance genes into the orchid gene pool. The ferredoxin-like protein gene originally isolated from sweet pepper is thought to function as a natural defense against infection due to its antimicrobial properties. Hence it was reasoned that introduction of this gene might produce Oncidium plants resistant to Erwinia carotovora, the causal agent for the soft rot disease. An expression vector containing sweet pepper ferredoxin-like protein (pflp) cDNA, hph and gusA coding sequence was successfully transformed into protocorm-like bodies (PLBs) of Oncidium orchid, using Agrobacterium tumefaciens strain EHA105. A total of 17 independent transgenic orchid lines was obtained, out of which six transgenic lines (beta-glucuronidase (GUS) positive) were randomly selected and confirmed by Southern, northern and western blot analyses. A bioassay was conducted on the transgenic lines. Transgenic plants showed enhanced resistance to E. carotovora, even when the entire plant was challenged with the pathogen. Our results suggest that pflp may be an extremely useful gene for genetic engineering strategies in orchids to confer resistance against soft rot disease.

Sweet pepper ferredoxin-like protein ( pflp) gene as a novel selection marker for orchid transformation

A novel method for selection of transgenic plants utilizing the sweet pepper ( Capsicum annuum L.) ferredoxin-like protein ( pflp) gene as selection marker and Erwinia carotovora as the selection agent has been developed. An expression vector containing a pflp cDNA driven by a cauliflower mosaic virus 35S promoter was successfully transformed into protocorm-like bodies of Oncidium orchid by Agrobacterium tumefaciens and particle bombardment, respectively. Erwinia carotovora was used as a selection agent to screen transformants, thereby obtaining transgenic plants without the use of an antibiotic selection agent. A total of 32 independent transgenic orchid lines were obtained, out of which 9 transgenic lines (beta-glucuronidase positive) were randomly selected and confirmed by Southern and northern blot analyses. The transgenic orchid plants showed enhanced resistance to E. carotovora, even when the entire plant was challenged with the pathogen. Our results suggest the novel use of the pflp gene as a resistance selection marker in plant genetic engineering strategies. In the future, the use of the pflp gene as a selection marker may facilitate the use of smaller gene constructs due to removal of bulky antibiotic selection and reporter genes. These constructs can then be used to incorporate additional genes of choice.

Ferredoxin from sweet pepper (Capsicum annuum L.) intensifying harpin(pss)-mediated hypersensitive response shows an enhanced production of active oxygen species (AOS)

The hypersensitive response (HR) is a form of cell death associated with plant resistance to pathogen infection. Harpin(pss), an elicitor from the bacterium Pseudomonas syringae pv. syringae, induces a HR in non-host plants. Previously, we reported an amphipathic protein from sweet pepper interfering with harpin(pss)-mediated HR. In this report, we isolated and characterized a cDNA clone encoded that amphipathic protein from sweet pepper. This protein is designated as PFLP (plant ferredoxin-like protein) by virtue of its high homology with plant ferredoxin protein containing an N-terminal signal peptide responsible for chloroplast targeting and a putative 2Fe-2S domain responsible for redox activity. Recombinant PFLP obtained from Escherichia coli was able to significantly increase active oxygen species (AOS) generation when mixed with harpin(pss) in tobacco suspension cells. It also showed enhanced HR when co-infiltrated with harpin(pss) in tobacco leaves. We used a transgenic tobacco suspension cells system that constitutively expresses the Pflp gene driven by the CaMV 35S promoter to study the function of PFLP in enhancing harpin(pss)-mediated hypersensitive cell death in vivo. In response to harpin(pss), suspension cells derived from Pflp transgenic tobacco showed a significant increase both in the generation of AOS and in cell death as compared to the wild type. AOS inhibitors diphenylene iodonium chloride (DPI) and lanthanum chlorate (LaCl3) were used to study the involvement of AOS in harpin(pss)-induced cell death. Our results demonstrate enhanced generation of AOS is necessary to cause enhanced hypersensitive cell death in Pflp transgenic tobacco cells and it is plasma membrane-bound NADPH-oxidase-dependent. Sub-cellular localization studies showed that PFLP is present in the cytoplasm and chloroplast of Pflp transgenic tobacco cells, but only in the chloroplast, not in the cytoplasm, of wild-type tobacco cells. It is possible that PFLP can change the redox state of the cell upon harpin(pss) inoculation to increase AOS generation and hypersensitive cell death. Overall, this study will provide a new insight in the functional properties of ferredoxin in hypersensitive cell death.

Constitutive expression of hrap gene in transgenic tobacco plant enhances resistance against virulent bacterial pathogens by induction of a hypersensitive response

Hypersensitive response-assisting protein (HRAP) has been previously reported as an amphipathic plant protein isolated from sweet pepper that intensifies the harpin(Pss)-mediated hypersensitive response (HR). The hrap gene has no appreciable similarity to any other known sequences, and its activity can be rapidly induced by incompatible pathogen infection. To assess the function of the hrap gene in plant disease resistance, the CaMV 35S promoter was used to express sweet pepper hrap in transgenic tobacco. Compared with wild-type tobacco, transgenic tobacco plants exhibit more sensitivity to harpin(Pss) and show resistance to virulent pathogens (Pseudomonas syringae pv. tabaci and Erwinia carotovora subsp. carotovora). This disease resistance of transgenic tobacco does not originate from a constitutive HR, because endogenous level of salicylic acid and hsr203J mRNA showed similarities in transgenic and wildtype tobacco under noninfected conditions. However, following a virulent pathogen infection in hrap transgenic tobacco, hsr203J was rapidly induced and a micro-HR necrosis was visualized by trypan blue staining in the infiltration area. Consequently, we suggest that the disease resistance of transgenic plants may result from the induction of a HR by a virulent pathogen infection.

Modified plication of the tunica albuginea in treating congenital penile curvature

OBJECTIVE

To describe a modified plication technique and compare the results with the Nesbit procedure for treating congenital penile curvature.

PATIENTS AND METHODS

Eleven men with congenital penile curvature were treated by a modified tunica albuginea plication technique. An artificial erection was induced by normal saline injection; in the areas where plication was planned, Buck's fascia was opened longitudinally and dissected a short distance toward the midline to free the neurovascular bundles. Allis clamps were used to grasp the tunica albuginea and "bumps" created. Two interrupted U-shaped sutures using 2/0 polyglactin were placed underneath each Allis clamp to secure the bump. The results were analysed retrospectively and compared with the results of 11 other men treated using the Nesbit procedure.

RESULTS

The mean (range) follow-up was 25 (12-47) months for the Nesbit procedure and 15 (8-26) months for the modified plication procedure. In the Nesbit group, eight patients had satisfactory cosmetic and functional results; three complained of penile shortening and one had erectile dysfunction. In the modified plication group, 10 patients reported satisfactory cosmetic and functional results; one complained of penile shortening, two were concerned about the indurations of the penis but none had erectile dysfunction.

CONCLUSIONS

The modified plication technique is easier to perform, is more often successful and causes fewer surgical complications than the Nesbit procedure for treating congenital penile curvature.

Coronary artery stenosis in rats affects beta-adrenergic receptor signaling in myocytes

OBJECTIVE

The purpose of this study was to determine whether the early chronic ischemic cardiomyopathy produced by non-occlusive coronary artery constriction was characterized by alterations in the regulation of beta-adrenoreceptor (beta-AR) signaling.

METHODS

Coronary artery narrowing was surgically induced in rats and the animals sacrificed at 7 and 14 days. The changes in the biochemical properties of the multiple components of the beta-AR pathway were examined in enzymatically dissociated myocytes.

RESULTS

Coronary stenosis, involving an average 55% reduction in luminal diameter, was associated with left ventricular failure and right ventricular dysfunction at both time intervals. A decrease in the quantity of beta-AR was detected at 7 days and preceded the loss of high-affinity binding sites. This regulatory modification was characterized by a reduction in beta 1 and beta 2 receptors and a shift in the isoproterenol dose response curve indicating a functional correlation between the decrease in beta-AR and attenuated inotropic support of the myocardium. The percentage of beta-AR binding agonist with high affinity decreased significantly at 14 days along with a further reduction in the density of beta 1 and beta 2 receptors. Reconstitution studies with cyc S49 lymphoma cells did not detect an impairment of Gs alpha functional activity, but the quantity of Gi alpha was increased at both intervals. Finally, activation of the catalytic unit of adenylyl cyclase by forskolin and GTP was not altered by coronary stenosis, however, basal cyclic AMP in myocytes was depressed at 14 days.

CONCLUSIONS

Coronary stenosis induces distinct and progressive modifications in the beta-AR signaling cascade which may contribute to the impaired ventricular performance in this model of myocardial ischemia.

[Complications of percutaneous renal biopsy: an analysis of 1000 consecutive biopsies]

The complications of percutaneous renal biopsies in 1000 cases are analysed in this paper. Because the modern techniques for biopsy localization and operation were used, both accidental puncture of other organs and infection were avoided. However, the hemorrhage of renal wound was still a predominate complication. Gross hematuria developed in 7.4% of biopsies, perirenal hematomas 4.4% of biopsies, and serious renal bleeding complications, including arteriovenous fistula, requiring transfusion of more than 1000 ml of blood were detected in 0.6% of biopsies. In this paper the manifestations, diagnosis and treatment for every renal bleeding complication are discussed. It is emphasized that renal arteriography should be done for the patients with persistent or recurrent renal hemorrhage, and that selective arterial embolization by using self-blood coagulative pieces should be considered before deciding surgical correction of these serious bleeding complications.

ANG II receptors, c-myc, and c-jun in myocytes after myocardial infarction and ventricular failure

To determine the relationship between reactive cardiac hypertrophy and the expression of angiotensin II (ANG II) receptors in surviving myocytes after infarction, large infarcts were produced in rats that were killed 2-3 days later. Measurements of global ventricular dynamics indicated that left ventricular failure and right ventricular dysfunction occurred in experimental animals. These alterations in ventricular pump function were associated with increases in ventricular weight-to-body weight ratio, indicative of developing cardiac hypertrophy. Such a response was coupled with a 6.6-fold increase in ANG II receptor mRNA in myocytes from the left ventricle. A 2.3-fold increase in the expression of ANG II receptor in myocytes from the right ventricle was also found. Radioligand binding assay documented a 44% increase in the density of ANG II receptors on left ventricular myocytes of infarcted hearts. To establish whether the induction of genes commonly associated with myocyte hypertrophy was present, the message for c-myc and c-jun was biventricularly assessed. Myocardial infarction was accompanied by overexpressions of c-myc and c-jun that were more prominent in left than in right ventricular myocytes. In conclusion, the enhanced expression of ANG II receptor and its receptor protein and c-myc and c-jun in myocytes may participate in the reactive growth processes of these cells after infarction.