bluuebunny/crossref_metadata_2025_split huggingface dataset:
Membrane topology and sequence requirements for oil body targeting of oleosin
Authors: Abell Ben M. , Hahn Margaret , Holbrook Larry A. , Moloney Maurice M. 
Published: December 2004

SummaryOleosin protein is targeted to oil bodies via the endoplasmic reticulum (ER) and consists of a lipid‐submerged hydrophobic (H) domain that is flanked by cytosolic hydrophilic domains. We investigated the relationship between oleosin ER topology and its subsequent ability to target to oil bodies. Oleosin variants were created to yield differing ER membrane topologies and tagged with a reporter enzyme. Localisation was assessed by fractionation after transient expression in embryonic cells. Membrane‐straddled topologies with N‐terminal sequence in the ER lumen and C‐terminal sequence in the cytosol were unable to target to oil bodies efficiently. Similarly, a translocated topology with only ER membrane and lumenal sequence was unable to target to oil bodies efficiently. Both topology variants accumulated proportionately higher in ER microsomal fractions, demonstrating a block in transferring from ER to oil bodies. The residual oil body accumulation for the inverted topology was shown to be because of partial adoption of native ER membrane topology, using a reporter variant, which becomes inactivated by ER‐mediated glycosylation. In addition, the importance of H domain sequence for oil body targeting was assessed using variants that maintain native ER topology. The central proline knot motif (PKM) has previously been shown to be critical for oil body targeting, but here the arms of the H domain flanking this motif were shown to be interchangeable with only a moderate reduction in oil body targeting. We conclude that oil body targeting of oleosin depends on a specific ER membrane topology but does not require a specific sequence in the H domain flanking arms.
Membrane‐bound fatty acid desaturases are inserted co‐translationally into the ER and contain different ER retrieval motifs at their carboxy termini
Authors: McCartney Andrew W. , Dyer John M. , Dhanoa Preetinder K. , Kim Peter K. , Andrews David W. , McNew James A. , Mullen Robert T. 
Published: December 2004

SummaryFatty acid desaturases (FADs) play a prominent role in plant lipid metabolism and are located in various subcellular compartments, including the endoplasmic reticulum (ER). To investigate the biogenesis of ER‐localized membrane‐bound FADs, we characterized the mechanisms responsible for insertion of Arabidopsis FAD2 and Brassica FAD3 into ER membranes and determined the molecular signals that maintain their ER residency. Using in vitro transcription/translation reactions with ER‐derived microsomes, we show that both FAD2 and FAD3 are efficiently integrated into membranes by a co‐translational, translocon‐mediated pathway. We also demonstrate that while the C‐terminus of FAD3 (‐KSKIN) contains a functional prototypic dilysine ER retrieval motif, FAD2 contains a novel C‐terminal aromatic amino acid‐containing sequence (‐YNNKL) that is both necessary and sufficient for maintaining localization in the ER. Co‐expression of a membrane‐bound reporter protein containing the FAD2 C‐terminus with a dominant‐negative mutant of ADP‐ribosylation factor (Arf)1 abolished transient localization of the reporter protein in the Golgi, indicating that the FAD2 peptide signal acts as an ER retrieval motif. Mutational analysis of the FAD2 ER retrieval signal revealed a sequence‐specific motif consisting of Φ‐X‐X‐K/R/D/E‐Φ‐COOH, where ‐Φ‐ are large hydrophobic amino acid residues. Interestingly, this aromatic motif was present in a variety of other known and putative ER membrane proteins, including cytochrome P450 and the peroxisomal biogenesis factor Pex10p. Taken together, these data describe the insertion and retrieval mechanisms of FADs and define a new ER localization signal in plants that is responsible for the retrieval of escaped membrane proteins back to the ER.
Heterosis in the freezing tolerance of crosses between two Arabidopsis thaliana accessions (Columbia‐0 and C24) that show differences in non‐acclimated and acclimated freezing tolerance
Authors: Rohde Peter , Hincha Dirk K. , Heyer Arnd G. 
Published: December 2004

SummaryHeterosis is broadly defined as the increased vigour of hybrids in comparison to their parents. In the model plant Arabidopsis thaliana, a significant heterosis effect on leaf‐freezing tolerance was observed in the F1 generation of a cross between the accessions Columbia‐0 (Col) and C24. Parental Col plants were significantly more freezing‐tolerant than C24 plants in both the acclimated and non‐acclimated (NA) states. Mid‐parent heterosis was observed in the F1 plants, both in the basic tolerance of non‐adapted plants and in freezing tolerance after cold acclimation. Best‐parent heterosis, on the other hand, was only found after cold acclimation. The heterosis effect was reduced in the F2 populations such that only mid‐parent heterosis was evident. The leaf content of soluble sugars (fructose (Fru), glucose (Glc), sucrose (Suc) and raffinose (Raf)) increased dramatically in the F1 plants after cold acclimation as compared to the parental lines. The content of proline (Pro), however, was only moderately increased in the F1 plants under the same conditions. Correlation analyses showed that only Raf content was consistently related to leaf‐freezing tolerance in both the acclimated and NA states. A quantification of mRNA levels in leaves of parental and F1 lines using quantitative real‐time RT‐PCR showed no clear indication for an involvement of the investigated genes (CBF (C‐repeat binding factor)1, CBF2, (cold‐regulated protein (COR) 6.6, COR15a, COR15b, COR47 and COR78) in the heterosis effect.
The nuclear factor HCF145 affects chloroplast psaA‐psaB‐rps14 transcript abundance in Arabidopsis thaliana
Authors: Lezhneva Lina , Meurer Jörg 
Published: December 2004

SummaryThe high chlorophyll fluorescence (hcf)145 mutant of Arabidopsis thaliana is specifically affected in photosystem (PS)I function as judged from spectroscopic analysis of PSII and PSI activity. The defect is because of a severe deficiency of PSI core subunits, whereas levels of the four outer antenna subunits of PSI were less reduced in hcf145. Pulse labelling of chloroplast proteins indicated that synthesis of the two largest PSI reaction‐centre polypeptides, Psa (photosystem I subunit) A and PsaB, is significantly affected by the mutation. A comparison of stationary transcript levels with rates of transcription demonstrates that hcf145 induces a decreased stability and, probably, transcription of the tricistronic psaA‐psaB‐rps (small‐subunit ribosomal protein)14 mRNA, which is generated by the plastid‐encoded RNA polymerase. Translation inhibition experiments excluded translational defects as primary cause of impaired mRNA stability. Larger primary transcripts, which also contain sequences of the ycf3 (hypothetical chloroplast reading frame) gene located upstream of the psaA‐psaB‐rps14 operon and generated by the action of the nuclear‐encoded RNA polymerase, are not targeted by the mutation. Real‐time reverse transcription (RT)‐PCR analysis has successfully been applied to quantify defined intervals of the tricistronic transcript and it was established that the psaA region is less stable than the rps14 region in hcf145. The hcf145 gene has been mapped on the upper part of chromosome 5.
A modified viral satellite DNA that suppresses gene expression in plants
Authors: Tao Xiaorong , Zhou Xueping 
Published: December 2004

SummaryDNAβ is a type of single‐stranded (ss) circular satellite DNA found in association with monopartite‐genome begomoviruses, such as Tomato yellow leaf curl China virus isolate Y10 (TYLCCNV‐Y10). Y10 DNAβ is required for symptom expression in plants but depends on TYLCCNV‐Y10 genomic DNA (DNA‐A) for replication and encapsidation. When we converted DNAβ into a gene‐silencing vector (modified DNAβ (DNAmβ)) by replacing its C1 open‐reading frame (ORF) with a multiple cloning site (MCS), it was replicated but no longer induced symptoms in association with TYLCCNV‐Y10 DNA‐A, so allowing the effects of gene inserts to be recognized easily. Insertion into DNAmβ of sequences from any of the three host genes (proliferating cell nuclear antigen (PCNA), phytoene desaturase (PDS), and sulfur (Su)), or from a transgene (green fluorescent protein (GFP)), resulted in silencing of the cognate gene in Nicotiana benthamiana. The silencing persisted for more than a month and was associated with decreased levels of mRNA of the gene targeted. Although DNAmβ probably does not enter meristematic tissue, the PCNA gene could be silenced there. DNAmβ was an effective silencing vector in tested N. glutinosa, N. tabacum Samsun (NN or nn), and Lycopersicon esculentum plants, and was able to silence two genes simultaneously. This satellite DNA vector‐based form of virus‐induced gene silencing (VIGS) promises to be applicable to other begomovirus/DNAβ systems, which are recently reported to occur in several dicotyledonous crop species, thereby providing a powerful approach to gene discovery and the analysis of gene function in these crops.
Chromatin techniques for plant cells
Authors: Bowler Chris , Benvenuto Giovanna , Laflamme Pierre , Molino Diana , Probst Aline V. , Tariq Muhammad , Paszkowski Jerzy 
Published: December 2004

SummaryA large number of recent studies have demonstrated that many important aspects of plant development are regulated by heritable changes in gene expression that do not involve changes in DNA sequence. Rather, these regulatory mechanisms involve modifications of chromatin structure that affect the accessibility of target genes to regulatory factors that can control their expression. The central component of chromatin is the nucleosome, containing the highly conserved histone proteins that are known to be subject to a wide range of post‐translational modifications, which act as recognition codes for the binding of chromatin‐associated factors. In addition to these histone modifications, DNA methylation can also have a dramatic influence on gene expression. To accommodate the burgeoning interest of the plant science community in the epigenetic control of plant development, a series of methods used routinely in our laboratories have been compiled that can facilitate the characterization of putative chromatin‐binding factors at the biochemical, molecular and cellular levels.
AtPTR1, a plasma membrane peptide transporter expressed during seed germination and in vascular tissue of Arabidopsis
Authors: Dietrich Daniela , Hammes Ulrich , Thor Kathrin , Suter‐Grotemeyer Marianne , Flückiger Ricardo , Slusarenko Alan J. , Ward John M. , Rentsch Doris 
Published: December 2004

SummaryFor the efficient translocation of organic nitrogen, small peptides of two to three amino acids are posited as an important alternative to amino acids. A new transporter mediating the uptake of di‐ and tripeptides was isolated from Arabidopsis thaliana by heterologous complementation of a peptide transport‐deficient Saccharomyces cerevisiae mutant. AtPTR1 mediated growth of S. cerevisiae cells on different di‐ and tripeptides and caused sensitivity to the phytotoxin phaseolotoxin. The spectrum of substrates recognized by AtPTR1 was determined in Xenopus laevis oocytes injected with AtPTR1 cRNA under voltage clamp conditions. AtPTR1 not only recognized a broad spectrum of di‐ and tripeptides, but also substrates lacking a peptide bond. However, amino acids, ω‐amino fatty acids or peptides with more than three amino acid residues did not interact with AtPTR1. At pH 5.5 AtPTR1 had an apparent lower affinity (K0.5 = 416 μm) for Ala‐Asp compared with Ala‐Ala (K0.5 = 54 μm) and Ala‐Lys (K0.5 = 112 μm). Transient expression of AtPTR1/GFP fusion proteins in tobacco protoplasts showed that AtPTR1 is localized at the plasma membrane. In addition, transgenic plants expressing the β‐glucuronidase (uidA) gene under control of the AtPTR1 promoter demonstrated expression in the vascular tissue throughout the plant, indicative of a role in long‐distance transport of di‐ and tripeptides.
Potassium carrier TRH1 is required for auxin transport in Arabidopsis roots
Authors: Vicente‐Agullo Francisco , Rigas Stamatis , Desbrosses Guilhem , Dolan Liam , Hatzopoulos Polydefkis , Grabov Alexander 
Published: December 2004

SummaryDisruption of the TRH1 potassium transporter impairs root hair development in Arabidopsis, and also affects root gravitropic behaviour. Rescue of these morphological defects by exogenous auxin indicates a link between TRH1 activity and auxin transport. In agreement with this hypothesis, the rate of auxin translocation from shoots to roots and efflux of [3H]IAA in isolated root segments were reduced in the trh1 mutant, but efflux of radiolabelled auxin was accelerated in yeast cells transformed with the TRH1 gene. In roots, ProTRH1:GUS expression was localized to the root cap cells which are known to be the sites of gravity perception and are central for the redistribution of auxin fluxes. Consistent with these findings, auxin‐dependent DR5:GUS promoter‐reporter construct was misexpressed in the trh1 mutant indicating that partial block of auxin transport through the root cap is associated with upstream accumulation of the phytohormone in protoxylem cells. When [K+] in the medium was reduced from 20 to 0.1 mm, wild type roots showed mild agravitropic phenotype and DR5:GUS misexpression in stelar cells. This pattern of response to low external [K+] was also affected by trh1 mutation. We conclude that the TRH1 carrier is an important part of auxin transport system in Arabidopsis roots.
A subset of hypersensitive response marker genes, includingHSR203J, is the downstream target of a spermine signal transduction pathway in tobacco
Authors: Takahashi Yoshihiro , Uehara Yukiko , Berberich Thomas , Ito Akiko , Saitoh Hiromasa , Miyazaki Atsushi , Terauchi Ryohei , Kusano Tomonobu 
Published: December 2004

SummaryA cellular signal transduction pathway induced by the polyamine, spermine (Spm), and transmitted by mitochondrial dysfunction is proposed in tobacco. In this investigation, we further resolve the pathway by identifying a subset of hypersensitive response (HR) marker genes as downstream components. In a previous report, we identified harpin‐induced 1 (HIN1) and two closely related genes as responsive to Spm. Other HR marker genes,HSR203J,HMGR,HSR201, andHSR515, are also Spm‐responsive. Induction of these HR marker genes, includingHIN1, by Spm was suppressed by pre‐treatment with antioxidants, calcium channel blockers, inhibitor of mitochondrial permeability transition pore openings, and blockers of amine oxidase/polyamine oxidase. Such quenching is also observed for Spm‐induced activation of two mitogen‐activated protein kinases (MAPKs), salicylic acid‐induced protein kinase (SIPK), and wound‐induced protein kinase (WIPK), and upregulation of theWIPKgene, suggesting that all these components are part of the same signaling pathway. Furthermore, gain‐of‐function and loss‐of‐function studies on MAPK cascade members reveal that the expression of Spm‐induced HR marker genes varies with respect to involvement of SIPK/WIPK activation.
WRINKLED1 encodes an AP2/EREB domain protein involved in the control of storage compound biosynthesis in Arabidopsis
Authors: Cernac Alex , Benning Christoph 
Published: December 2004

SummaryThe accumulation of storage compounds during seed development ensures the survival of the young seedling, and also provides nutrition to humans and animals in the form of foods and feeds. The putative AP2/EREBP transcription factor WRINKLED1 (WRI1) is involved in the regulation of seed storage metabolism in Arabidopsis. A splicing mutant allele, wri1‐1, caused the reduction of seed oil accumulation. Glycolysis was compromised in this mutant, rendering developing embryos unable to efficiently convert sucrose into precursors of triacylglycerol biosynthesis. Expression of the WRINKLED1 cDNA under the control of the cauliflower mosaic virus 35S‐promoter led to increased seed oil content. Moreover, the ectopic expression of the WRINKLED1 cDNA caused the accumulation of triacylglycerols in developing seedlings. This effect depended upon the presence of glucose in the growth medium or other sugars readily metabolized to glucose. Oil‐accumulating seedlings showed aberrant development consistent with a prolonged embryonic state.
Outbreak of West Nile virus causing severe neurological involvement in children, Nuba Mountains, Sudan, 2002
Authors: Depoortere Evelyn , Kavle Justine , Keus Kees , Zeller Hervé , Murri Séverine , Legros Dominique 
Published: December 2004

SummaryAn atypical outbreak of West Nile virus (WNV) occurred in Ngorban County, South Kordophan, Sudan, from May to August 2002. We investigated the epidemic and conducted a case–control study in the village of Limon. Blood samples were obtained for cases and controls. Patients with obvious sequelae underwent cerebrospinal fluid (CSF) sampling as well. We used enzyme‐linked immunosorbent assay (ELISA) and neutralization tests for laboratory diagnosis and identified 31 cases with encephalitis, four of whom died. Median age was 36 months. Bivariate analysis did not reveal any significant association with the risk factors investigated. Laboratory analysis confirmed presence of IgM antibodies caused by WNV in eight of 13 cases, indicative of recent viral infection. The unique aspects of the WNW outbreak in Sudan, i.e. disease occurrence solely among children and the clinical domination of encephalitis, involving severe neurological sequelae, demonstrate the continuing evolution of WNV virulence. The spread of such a virus to other countries or continents cannot be excluded.
Quantitative evaluation of integrated schistosomiasis control: the example of passive case finding in Ghana
Authors: De Vlas Sake J. , Danso‐Appiah Anthony , Van Der Werf Marieke J. , Bosompem Kwabena M. , Habbema J. Dik F. 
Published: December 2004

SummaryPassive case finding based on adequate diagnosis and treatment of symptomatic individuals with praziquantel by the health care facilities is a minimum requirement for integrated schistosomiasis control. Two field studies were conducted in Ghana to obtain quantifications about the steps in this process: (1) a study of health‐seeking behaviour through interview of individuals with reported schistosomiasis‐related symptoms; (2) a study of the performance of the Ghanaian health system with regard to schistosomiasis case management by presenting clinical scenarios to health workers and collecting information about availability of praziquantel. It appeared that cases of blood in urine (the most typical symptom of Schistosoma haematobium) and blood in stool (the most typical symptom of S. mansoni) have a very small probability of receiving praziquantel (4.4% and 1.4%, respectively) from health facilities. Programmes aimed at making the drug available at all levels of the health care delivery system and encouraging health‐seeking behaviour through health education are not likely to increase these probabilities beyond 30%. This is because many cases with blood in urine do not consider it serious enough to seek health care, and blood in stool usually requires (imperfect) diagnostic testing and referral. We therefore conclude that additional control activities, especially for high‐risk groups, will remain necessary.
Disease control in primary health care: a historical perspective
Authors: Van Balen Harrie 
Published: December 2004

SummaryThe effectiveness of disease control by mobile teams decreased when countries became independent. Early case‐finding and continuity of care require permanently accessible health care facilities where rationalization by professionals and participation of the users are well balanced. The Primary Health Care concept, a plea for this equilibrium, has been discredited by different types of misapplication. Correctly functioning and accessible first line health services, completed by a referral level, are a precondition for effective participation of the users. Where ‘ideal health districts’ cannot be realized, a form of steady exchanges between generalists and the specialists of the referral level has lead to diverse ‘functional districts’.
The practical importance of permanent and semipermanent habitats for controlling aquatic stages of Anopheles gambiae sensu lato mosquitoes: operational observations from a rural town in western Kenya
Authors: Fillinger Ulrike , Sonye George , Killeen Gerry F. , Knols Bart G. J. , Becker Norbert 
Published: December 2004

SummaryControl of aquatic‐stage Anopheles is one of the oldest and most historically successful interventions to prevent malaria, but it has seen little application in Africa. Consequently, the ecology of immature afrotropical Anopheles has received insufficient attention. We therefore examined the population dynamics of African anopheline and culicine mosquitoes using operationally practicable techniques to examine the relative importance and availability of different larval habitats in an area of perennial malaria transmission in preparation for a pilot‐scale larval control programme. The study was conducted in Mbita, a rural town on the shores of Lake Victoria in Western Kenya, over 20 months. Weekly larval surveys were conducted to identify the availability of stagnant water, habitat characteristics and larval densities. Adult mosquitoes were collected indoors at fortnightly intervals. Availability of aquatic habitats and abundance of mosquito larvae were directly correlated with rainfall. Adult mosquito densities followed similar patterns but with a time‐lag of approximately 1 month. About 70% of all available habitats were man‐made, half of them representing cement‐lined pits. On average, 67% of all aquatic habitats on a given sampling date were colonized by Anopheles larvae, of which all identified morphologically were A. gambiae sensu lato. Natural and artificial habitats were equally productive over the study period and larval densities were positively correlated with presence of tufts of low vegetation and negatively with non‐matted algal content. The permanence of a habitat had no significant influence on larval productivity. We conclude that A. gambiae is broadly distributed across a variety of habitat types, regardless of permanence. All potential breeding sites need to be considered as sources of malaria risk at any time of the year and exhaustively targeted in any larval control intervention.
Clinical microbicide research: an overview
Authors: Damme Lut Van 
Published: December 2004

SummaryAt the end of 2003, 42 million people were HIV infected and the epidemic continues to spread, despite the availability and effectiveness of male condoms. For many women negotiating condom use is not feasible. Therefore there is an urgent need for a female controlled method for HIV prevention. This article gives an overview of the clinical research done with microbicides, chemicals with the potential to prevent an HIV infection. In the 1990s most research was done with spermicides, mainly nonoxynol‐9. Since the results of the COL‐1492 trial became available, new products were evaluated and some of them are now in phase III trials.