bluuebunny/crossref_metadata_2025_split huggingface dataset:
Isolation and characterization of signal transduction mutants of Arabidopsis thaliana that constitutively activate the octadecanoid pathway and form necrotic microlesions
Authors: Hilpert Bernadette , Bohlmann Holger , Den Camp Roel op , Przybyla Dominika , Miersch Otto , Buchala Anthony , Apel Klaus 
Published: March 2003

SummaryThionins are a group of antimicrobial polypeptides that form part of the plant's defense mechanism against pathogens. The Thi 2.1 thionin gene of Arabidopsis thaliana has been shown to be inducible by jasmonic acid (JA), an oxylipin‐like hormone derived from oxygenated linolenic acid and synthesized via the octadecanoid pathway. The JA‐dependent regulation of the Thi 2.1 gene has been exploited for setting up a genetic screen for the isolation of signal transduction mutants that constitutively express the Thi 2.1 gene. Ten cet‐mutants have been isolated which showed a constitutive expression of the thionin gene. Allelism tests revealed that they represent at least five different loci. Some mutants are dominant, others recessive, but all cet mutations behaved as monogenic traits when backcrossed with Thi 2.1‐GUS plants. Some of the mutants overproduce JA and its bioactive precursor 12‐oxophytodienoic acid (OPDA) up to 40‐fold while others have the same low levels as the control wildtype plants. Two of the mutants showed a strong induction of both the salicylic acid (SA)‐ and the JA‐dependent signaling pathways, while the majority seems to be affected only in the octadecanoid pathway. The Thi 2.1 thionin gene and the Pdf 1.2 defensin gene are activated independently, though both are regulated by JA. The cet‐mutants, except for one, also show a spontaneous leaf cell necrosis, a reaction often associated with the systemic acquired resistance (SAR) pathway.
E2F sites that can interact with E2F proteins cloned from rice are required for meristematic tissue‐specific expression of rice and tobacco proliferating cell nuclear antigen promoters
Authors: Kosugi Shunichi , Ohashi Yuko 
Published: March 2003

SummaryPlants have recently been found to have E2F‐like and Rb‐like proteins, regulators responsible for the G1(G0)‐S phase transition of the cell cycle in animals. Here we show that E2F is involved in transcription of plant genes for proliferating cell nuclear antigen (PCNA), which is required for DNA replication. Potential E2F binding sites found in the rice PCNA promoters mediated transcriptional activation in actively dividing cells and tissues of tobacco, but not transcriptional repression in terminally differentiated tissues, as also observed for the PCF binding sites previously found in the rice promoter. Similar results were obtained from analyses for a PCNA promoter isolated from tobacco, which contained two E2F‐like sites, each with a different degree of contribution to the promoter activation. These E2F‐like sites except for a rice site were indeed bound specifically by recombinant proteins of rice E2F, OsE2F1 and OsE2F2, and complexes of OsE2F1 with Arabidopsis DP proteins. Furthermore, OsE2F1 had the ability to transactivate an E2F‐reporter gene containing the tobacco E2F site on co‐expression with an Arabidopsis DP, and the transactivation was greatly enhanced by tagging a canonical nuclear localization signal to OsE2F1, suggesting a nuclear import‐mediated regulation of the OsE2F1 function. In addition, we found that a large number of replication‐ and mismatch repair‐associated genes in Arabidopsis contain E2F binding sequences conserved in their predicted promoter regions.
The ArabidopsisREF8 gene encodes the 3‐hydroxylase of phenylpropanoid metabolism
Authors: Franke Rochus , Humphreys John M. , Hemm Matthew R. , Denault Jeff W. , Ruegger Max O. , Cusumano Joanne C. , Chapple Clint 
Published: March 2003

SummaryThe activity of p‐coumarate 3‐hydroxylase (C3H) is thought to be essential for the biosynthesis of lignin and many other phenylpropanoid pathway products in plants; however, no conditions suitable for the unambiguous assay of the enzyme are known. As a result, all attempts to purify the protein and clone its corresponding gene have failed. By screening for plants that accumulate reduced levels of soluble fluorescent phenylpropanoid secondary metabolites, we have identified a number of Arabidopsis mutants that display a reduced epidermal fluorescence (ref) phenotype. Using radiotracer‐feeding experiments, we have determined that the ref8 mutant is unable to synthesize caffeic acid, suggesting that the mutant is defective in a gene required for the activity or expression of C3H. We have isolated the REF8 gene using positional cloning methods, and have verified that it encodes C3H by expression of the wild‐type gene in yeast. Although many previous reports in the literature have suggested that C3H is a phenolase, the isolation of the REF8 gene demonstrates that the enzyme is actually a cytochrome P450‐dependent monooxygenase. Although the enzyme accepts p‐coumarate as a substrate, it also exhibits significant activity towards other p‐hydroxylated substrates. These data may explain the previous difficulties in identifying C3H activity in plant extracts and they indicate that the currently accepted version of the lignin biosynthetic pathway is likely to be incorrect.
Fucosylated arabinogalactan‐proteins are required for full root cell elongation in arabidopsis
Authors: Van Hengel Arjon J. , Roberts Keith 
Published: March 2003

SummaryThe Arabidopsis thaliana mutant mur1 is affected in the biosynthesis of l‐fucose and has less than 2% of the normal amounts of this sugar in the cell walls of its aerial parts. Although in roots the reduction of l‐fucose is only 40%, this causes a decrease of about 50% in root cell elongation. Since arabinogalactan‐proteins (AGPs) are known to play a role in plant cell expansion we studied the composition of mur1 root AGPs. Arabidopsis root AGPs were shown to contain l‐fucose, which was reduced in level in mur1 AGPs. In wild‐type plants, an l‐fucose containing epitope is present in AGPs in the cell wall of differentiating root cells. Addition of eel lectin, which specifically recognizes this epitope, and not fucose in other wall polymers, can phenocopy mur1 roots. Several lines of evidence are presented to support the contention that l‐fucose containing root AGPs are required for the full elongation of root cells.
Phototropin LOV domains exhibit distinct roles in regulating photoreceptor function
Authors: Christie John M. , Swartz Trevor E. , Bogomolni Roberto A. , Briggs Winslow R. 
Published: March 2003

SummaryPhototropins (phot1 and phot2) are autophosphorylating serine/threonine kinases that function as photoreceptors for phototropism, light‐induced chloroplast movement, and stomatal opening in Arabidopsis. The N‐terminal region of phot1 and phot2 contains two specialized PAS domains, designated LOV1 and LOV2, which function as binding sites for the chromophore flavin mononucleotide (FMN). Both LOV1 and LOV2 undergo a self‐contained photocycle, which involves the formation of a covalent adduct between the FMN chromophore and a conserved active‐site cysteine residue (Cys39). Replacement of Cys39 with alanine abolishes the light‐induced photochemical reaction of LOV1 and LOV2. Here we have used the Cys39Ala mutation to investigate the role of LOV1 and LOV2 in regulating phototropin function. Photochemical analysis of a bacterially expressed LOV1 + LOV2 fusion protein indicates that LOV2 functions as the predominant light‐sensing domain for phot1. LOV2 also plays a major role in mediating light‐dependent autophosphorylation of full‐length phot1 expressed in insect cells and transgenic Arabidopsis. Moreover, photochemically active LOV2 alone in full‐length phot1 is sufficient to elicit hypocotyl phototropism in transgenic Arabidopsis, whereas photochemically active LOV1 alone is not. Further photochemical and biochemical analyses also indicate that the LOV1 and LOV2 domains of phot2 exhibit distinct roles. The significance for the different roles of the phototropin LOV domains is discussed.
On‐line measurements of K+ activity in the tensile water of the xylem conduit of higher plants
Authors: Wegner Lars H. , Zimmermann Ulrich 
Published: March 2003

SummaryIn higher plants the xylem is the main pathway for anti‐gravitational, long‐distance transport of nutrients and water from the root through the shoot to the upper leaves. In the xylem conduit water is in a metastable state if tension larger than 0.1 MPa (i.e. negative pressure) is developed. While diurnal changes in negative pressure of individual xylem vessels can quite accurately be recorded by the minimal‐invasive xylem pressure probe technique and water flow by non‐invasive NMR techniques, the problem of continuous monitoring of solute flow remains a hitherto unresolved challenge. As shown here, integration of a K+ selective and a potential measuring microelectrode into the xylem pressure probe allowed on‐line measurements of the K+ activity in individual xylem vessels of maize roots together with pressure and trans‐root potential, the potential difference between the xylem and the external medium (i.e. the overall driving force of ions through the root tissue). When light irradiation was increased from 10 µmol m−2 s−1 to 300 µmol m−2 s−1 and negative pressure developed in the vessel, xylem K+ activity dropped from 3.6 ± 2.6 mm to 0.9 ± 0.7 mm (n = 16), whereas the trans‐root potential depolarized from −2 ± 11 mV to + 12 ± 11 mV (n = 11), i.e. by + 14 ± 7 mV. The effect of light on all three parameters was reversible. Exposure of the root to various K+ activities in the bath ranging from 0.1 to 43 mm revealed that the K+ activity of the xylem sap was shielded against short‐term fluctuations in K+ supply to a large extent. In contrast, control experiments in which the root was cut 1 cm below the probe insertion point, allowing direct entry of external K+ into the xylem vessels, demonstrated that the xylem equilibrated rapidly with external K+. This was taken simultaneously as a proof for the correct reading of the probe.
Sulfate reduction is increased in transgenic Arabidopsis thaliana expressing 5′‐adenylylsulfate reductase from Pseudomonas aeruginosa
Authors: Tsakraklides George , Martin Melinda , Chalam Radhika , Tarczynski Mitchell C. , Schmidt Ahlert , Leustek Thomas 
Published: March 2003

SummaryThe two‐electron reduction of sulfate to sulfite in plants is mediated by 5′‐adenylylsulfate (APS) reductase, an enzyme theorized to be a control point for cysteine synthesis. The hypothesis was tested by expression in Arabidopsis thaliana under transcriptional control of the CaMV 35S promoter of the APS reductase from Pseudomonas aeruginosa (PaAPR) fused with the rbcS transit peptide for localization of the protein to plastids. PaAPR was chosen for the experiment because it is a highly stable enzyme compared with the endogenous APS reductase of A. thaliana, and because PaAPR is catalytically active in combination with the plant thioredoxins m and f indicating that it would likely be catalytically active in plastids. The results indicate that sulfate reduction and O‐acetylserine (OAS) production together limit cysteine synthesis. Transgenic A. thaliana lines expressing PaAPR accumulated sulfite, thiosulfate, cysteine, γ‐glutamylcysteine, and glutathione. Sulfite and thiosulfate increased more than did cysteine, γ‐glutamylcysteine and glutathione. Thiosulfate accumulation was most pronounced in flowers. Feeding of OAS to the PaAPR‐expressing plants caused cysteine and glutathione to increase more rapidly than in comparably treated wild type. Both wild‐type and transgenic plants accumulated sulfite and thiosulfate in response to OAS feeding. The PaAPR‐expressing plants were slightly chlorotic and stunted compared with wild type. An attempt to uncover the source of thiosulfate, which is not thought to be an intermediate of sulfate reduction, revealed that purified β‐mercaptopyruvate sulfurtransferase is able to form thiosulfate from sulfite and β‐mercaptopyruvate, suggesting that this class of enzymes could form thiosulfate in vivo in the presence of excess sulfite.
Developmental events and shoot apical meristem gene expression patterns during shoot development in Arabidopsis thaliana
Authors: Cary Andrew J. , Che Ping , Howell Stephen H. 
Published: March 2003

SummaryCritical developmental and gene expression profiles were charted during the formation of shoots from root explants in Arabidopsis tissue culture. Shoot organogenesis is a two‐step process involving pre‐incubation on an auxin‐rich callus induction medium (CIM) during which time root explants acquire competence to form shoots during subsequent incubation on a cytokinin‐rich shoot induction medium (SIM). At a histological level, the organization of shoot apical meristems (SAMs) appears to occur during incubation on SIM about the time of shoot commitment, i.e. the transition from hormone‐dependent to hormone‐independent shoot development. Genes involved in SAM formation, such as SHOOTMERISTEMLESS (STM) and CLAVATA1 (CLV1), were upregulated at about the time of shoot commitment, while WUSCHEL (WUS) was upregulated somewhat earlier. Genes required for STM expression, such as CUP‐SHAPED COTYLEDON 1 and 2 (CUC1 and 2) were upregulated prior to shoot commitment. Gene expression patterns were determined for two GFP enhancer trap lines with tissue‐specific expression in the SAM, including one line reporting on CUC1 expression. CUC1 was generally expressed in callus tissue during early incubation on SIM, but later CUC1 was expressed more locally in presumptive sites of shoot formation. In contrast, the expression pattern of the enhancer trap lines during zygotic embryogenesis was more localized to the presumptive SAM even in early stages of embryogenesis.
Interaction of NtCDPK1 calcium‐dependent protein kinase with NtRpn3 regulatory subunit of the 26S proteasome in Nicotiana tabacum
Authors: Lee Sang Sook , Cho Hye Sun , Yoon Gyeong Mee , Ahn Joon‐Woo , Kim Hyong‐Ha , Pai Hyun‐Sook 
Published: March 2003

SummaryUsing a yeast two‐hybrid system, we identified NtRpn3, a regulatory subunit of 26S proteasome, as an interacting protein of NtCDPK1 calcium‐dependent protein kinase in Nicotiana tabacum. Rpn3 in yeast is an essential protein involved in proteolysis of cell cycle regulatory proteins, and the carrot homolog of Rpn3 was previously isolated as a nuclear antigen that is mainly expressed in the meristem. NtCDPK1 physically interacts with NtRpn3 in vitro in a Ca2+‐independent manner and phosphorylates NtRpn3 in a Ca2+‐dependent manner with Mg2+ as a cofactor. NtCDPK1 and NtRpn3 are co‐localized in the nucleus, nuclear periphery, and around plasma membrane in vivo. Both NtCDPK1 and AtRpn3, an NtRpn3 homolog of Arabidopsis, are mainly expressed in the rapidly proliferating tissues including shoot and root meristems, and developing floral buds. Virus‐induced gene silencing of either NtRpn3 or NtCDPK1 resulted in the phenotypes of abnormal cell morphology and premature cell death in newly emerged leaves. Finally, NtCDPK1 interacts with NtRpn3 in vivo as shown by co‐immunoprecipitation. Based on these results, we propose that NtCDPK1 and NtRpn3 are interacting in a common signal transduction pathway possibly for regulation of cell division, differentiation, and cell death in tobacco.
Intravenous immunoglobulin: regulatory perspectives on use and supply
Authors: Farrugia A. , Poulis P. 
Published: March 2003

Technological advancements in the fractionation of plasma in the early 1970s led to the production of immunoglobulin preparations which could be administered intravenously. The ability to deliver larger doses than was possible with intramuscular products was accompanied by clinical studies demonstrating the efficacy of immunoglobulin treatment in a number of autoimmune and inflammatory conditions. This has led to a continuing increase in the usage of this product such that, currently, it is considered to be the driving force for plasma procurement. In recent years, difficulties have been experienced in the supply of this product in various markets.While intravenous immunoglobulins (IVIG) have undoubted clinical superiority over intramuscular products for the majority of indications, their use should be tempered with caution. Early clinical studies revealed that the risk of viral transmission from these products was higher than that of the traditional intramuscular presentation. This has had a profound impact on blood transfusion science as it has provided a major impetus for nucleic acid testing (NAT) for viral agents in blood donations. Perhaps less widely appreciated are the pressures which may be felt in blood services as the traditional drivers for plasma procurement – factor VIII and albumin – become secondary to IVIG. This review discusses the factors affecting the supply and safety of IVIG and the implications of recent global regulatory decisions on the delivery of this product and other therapeutic products derived from human plasma.
Risk factors for death in hospitalized dysentery patients in Rwanda
Authors: Legros Dominique , Paquet Christophe , Dorlencourt Fabienne , Le Saoult Elizabeth 
Published: March 2003

Summary To evaluate the management of severe dysentery cases in in‐patient facilities during an epidemic of Shigella dysenteriae type 1 (Sd1), and to identify the factors associated with the risk of death, we conducted a prospective cohort study in 10 Rwandese hospitals between September and December 1994. Data were obtained from 849 cases admitted to hospitals with diarrhoea and visible blood in stools. The proportion of patients with persistent bloody diarrhoea was 51.0% at treatment day 3 and 27.9% at treatment day 5. At discharge, 79.9% had improved or were cured. The case fatality ratio was 13.2%, higher for patients treated with nalidixic acid than for those treated with ciprofloxacin (12.2%vs. 2.2%, RR = 5.80, 95% CI = 0.83–40.72). In a logistic regression model three risk factors were significantly associated with an increased risk of death during hospitalization: severe dehydration on admission (adjusted OR = 2.79, 95% CI = 1.46–5.33), age over 50 (adjusted OR vs. 5–49 age group = 3.22, 95% CI = 1.70–6.11) and prescription of nalidixic acid (adjusted OR vs. ciprofloxacin = 8.66, 95% CI = 1.08–69.67). Those results were consistent with reported high levels of resistance of Sd1 to the commonest antibiotics, including nalidixic acid. Patients belonging to groups with a higher risk of dying should be given special medical attention and supportive care. In areas of high resistance to nalidixic acid, severe cases of dysentery should be treated with fluoroquinolones in order to reduce the mortality associated with these epidemics.
Determinants of mortality among children in the urban slums of Dhaka city, Bangladesh
Authors: Hussain Akhtar , Ali S. M. Keramat , Kvåle Gunnar 
Published: March 2003

Summary The growing slum population in the developing world is an increasing challenge for local health authorities. Little is known of the patterns of disease occurrence including treatment types offered in this population. The paper describes reported child mortality and its determinants, including the main diseases affecting children and treatments, in the slum population of Dhaka city, Bangladesh. 1500 households in three slum communities were included in a cross‐sectional survey. Reported death rates in the households per 1000 children (0–107 months) within the last year from the interview were 20.5 for boys and 27.0 for girls. More girls than boys died in infancy (age < 12 months). The most frequent reported causes of deaths were tetanus in infancy and diarrhoea among children aged ≤ 12 months. Vaccination coverage (DPT, polio, measles and BCG) was 73% for children < 3 years of age. The results showed that gender difference in mortality may have been influenced by the patterns of treatment received during sickness and the choice of treatment was determined by the financial ability of the households. Household income, children's vaccinations, TT immunization of mothers and personal cleanliness appeared to be significantly associated with child mortality. Despite the relatively high vaccination coverage for this population, child mortality remained alarmingly high, indicating that socioeconomic and environmental conditions must be improved to substantially reduce morbidity and mortality in this population.
Treatment of two patients with diffuse cutaneous leishmaniasis caused by Leishmania mexicana modifies the immunohistological profile but not the disease outcome
Authors: Salaiza‐Suazo Norma , Volkow Patricia , Pérez Tamayo Ruy , Moll Heidrun , Gillitzer Reinhard , Pérez‐Torres Armando , Pérez‐Montfort Ruy , Domínguez Jose Delgado , Velasco‐Castrejón Oscar , Crippa Marco , Becker Ingeborg 
Published: March 2003

Summary Two patients with diffuse cutaneous leishmaniasis caused by Leishmania mexicana were treated with two leishmanicidal drugs (pentamidine and allopurinol) combined with recombinant interferon‐γ restoring Th‐1 favouring conditions in the patients. Parasites decreased dramatically in the lesions and macrophages diminished concomitantly, while IL‐12‐producing Langerhans cells and interferon‐γ– producing NK and CD8 + lymphocytes increased in a reciprocal manner. The CD4+/CD8 + ratio in the peripheral blood normalized. During exogenous administration of interferon‐γ the parasites' capacity to inhibit the oxidative burst of the patients' monocytes was abolished. Even though Th‐1‐favouring conditions were restored, both patients relapsed two months after therapy was discontinued. We conclude that the tendency to develop a disease‐promoting Th‐2 response in DCL patients is unaffected by, and independent of, parasite numbers. Even though intensive treatment in DCL patients induced Th‐1 disease restricting conditions, the disease‐promoting immunomodulation of few persistent Leishmania sufficed to revert the immune response.
Pregnancy and HIV‐1 incidence in 178 married couples with discordant HIV‐1 serostatus: additional experience at an HIV‐1 counselling centre in the Democratic Republic of the Congo
Authors: Ryder R. W. , Kamenga C. , Jingu M. , Mbuyi N. , Mbu L. , Behets F. 
Published: March 2003

Summary To determine the effect of an HIV‐1 counselling programme on rates of HIV‐1 infection and pregnancy in a large group of married couples in Kinshasa, DRC with discordant HIV‐1 infection status, we conducted a baseline cross‐sectional HIV‐1 seroprevalence study in two large Kinshasa businesses. We identified 178 married couples (mean duration of marriage = 12.3 years) with discordant HIV‐1 serostatus (92 M+F‐/86 M‐F+). Seroincidence and pregnancy rates were observed during 310 person‐years of follow‐up (PYFU). The 92 M+F‐ couples had an HIV‐1 incidence of 3.7/100 PYFU and a pregnancy rate of 8.6/100. The 86 M‐F+ couples had a pregnancy rate of 6.8/100 PYFU and an HIV‐1 incidence of 6.8/100 PYFU. Couples seeking to have children but minimize their HIV‐1 transmission risk frequently had unprotected sex only during the woman's perceived monthly fertility period. This strategy resulted in the birth of 24 live‐born children and only one (4%; 95% CL = 0.0–21.6%) new HIV infection in couples having a child. Only 1 of 6 women who developed HIV‐1 infection (16.7%; 95 C.L. = 0–40.4%) became pregnant. While seronegative men had more extramarital sex once their wives' positive HIV‐1 infection status became known, most of these episodes involved safe sex. Divorce was rare. This study provides additional information concerning issues of safe sex in married couples with discordant HIV‐1 infection status, the dynamics of HIV transmission within couples and the effect of serostatus notification on the marriage and on intramarital and extramarital sexual behaviour in Kinshasa, Congo.