Genome maps 9. Arabidopsis thaliana. Wall chart.
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Arabidopsis↗
Biomedical subjects
C Lister
Publications and source records attributed to C Lister.
Development of an AFLP based linkage map of Ler, Col and Cvi Arabidopsis thaliana ecotypes and construction of a Ler/Cvi recombinant inbred line population.
An amplified fragment polymorphism (AFLP) based linkage map has been generated for a new Landsberg erecta/ Cape Verde Islands (Ler/Cvi) recombinant inbred line (RIL) population. A total of 321 molecular PCR based markers and the erecta mutation were mapped. AFLP markers were also analysed in the Landsberg erecta/Columbia (Ler/Col) RIL population (Lister and Dean, 1993) and 395 AFLP markers have been integrated into the previous Arabidopsis molecular map of 122 RFLPs, CAPSs and SSLPs. This enabled the evaluation of the efficiency and robustness of AFLP technology for linkage analyses in Arabidopsis. AFLP markers were found throughout the linkage map. The two RIL maps could be integrated through 49 common markers which all mapped at similar positions. Comparison of both maps led to the conclusion that segregating bands from a common parent can be compared between different populations, and that AFLP bands of similar molecular size, amplified with the same primer combination in two different ecotypes, are likely to correspond to the same locus. AFLPs were found clustering around the centromeric regions, and the authors have established the map position of the centromere of chromosome 3 by a quantitative analysis of AFLP bands using trisomic plants. AFLP markers were also used to estimate the polymorphism rate among the three ecotypes. The larger polymorphism rate found between Ler and Cvi compared to Ler and Col will mean that the new RIL population will provide a useful material to map DNA polymorphisms and quantitative trait loci.
Arabidopsis↗
The transposition frequency of Tag1 elements is increased in transgenic Arabidopsis lines.
Tag1 was identified as a highly active endogenous transposable element in transgenic Arabidopsis thaliana Landsberg erecta plants carrying the maize transposable element Activator (Ac). Here, we describe experiments designed to determine the basis for the high activity of Tag1. The frequency of transposition of Tag1 elements was compared in lines containing or lacking Ac transposase to assess the effect of Ac transposase on Tag1 activity. Three populations of nontransgenic plants, including nontransformed regenerants, were also analyzed. The high level of activity of Tag1 did not correlate with the presence or absence of Ac transposase but was significantly higher in transgenic lines. This result was maintained through at least six generations after transformation. These data suggest that Tag1 transposition is stimulated by processes that occur during the Agrobacterium transformation and that thereafter remain active. Two Tag1 elements are tightly linked in the Landsberg erecta genome and map to the lower arm of chromosome 1. Tag1 elements were found in only a few A. thaliana ecotypes but were present in four other Arabidopsis species.
Arabidopsis↗
FCA, a gene controlling flowering time in Arabidopsis, encodes a protein containing RNA-binding domains.
A strong promoter of the transition to flowering in Arabidopsis is encoded by FCA. FCA has been cloned and shown to encode a protein containing two RNA-binding domains and a WW protein interaction domain. This suggests that FCA functions in the posttranscriptional regulation of transcripts involved in the flowering process. The FCA transcript is alternatively spliced with only one form encoding the entire FCA protein. Plants carrying the FCA gene fused to the strong constitutive 35S promoter flowered earlier, and the ratio and abundance of the different FCA transcripts were altered. Thus, FCA appears to be a component of a posttranscriptional cascade involved in the control of flowering time.
Amino Acid Sequence↗
The future of dentistry.
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Dentistry, Operative↗
Cytosolic ascorbate peroxidase from Arabidopsis thaliana L. is encoded by a small multigene family.
A second cytosolic ascorbate peroxidase (cAPX; EC 1.11.1.11) gene from Arabidopsis thaliana has been characterised. This second gene (designated APX1b) maps to linkage group 3 and potentially encodes a cAPX as closely related to that from other dicotyledonous species as to the other member of this gene family (Kubo et al., 1993, FEBS Lett 315: 313 317; here designated APX1a), which maps to linkage group 1. In contrast, the lack of sequence similarity in non-coding regions of the genes implies that they are differentially regulated. Under non-stressed conditions only APX1a is expressed. APX1b was identified during low-stringency probing using a cDNA coding for pea cAPX which, in turn, was recovered from a cDNA library by immunoscreening with an antiserum raised against tea plastidial APX (pAPX). No pAPX cDNAs were recovered, despite the antiserum displaying specificity for pAPX in Western blots.
Amino Acid Sequence↗
Isolation and mapping of a new set of 129 RFLP markers in Arabidopsis thaliana using recombinant inbred lines.
A new collection of 129 Arabidopsis thaliana RFLP markers has been established based upon DNA fragments cloned in the pUC119 plasmid vector and insert end sequences of P1 clones. Dominant/null alleles affecting low-copy number sequences account for nine of the mapped polymorphisms, suggesting that deletions are not rare in A. thaliana. Recombinant inbred (RI) lines were used for mapping these marker loci. RI line-based mapping allows integration of this set of markers with markers previously reported as well as with any markers mapped in the future using this replenishable mapping resource. These markers are useful for map-based gene isolation and genome physical mapping in A. thaliana as well as studies of chromosome colinearity (synteny) with related species.
Arabidopsis↗
Use of Ac as an insertional mutagen in Arabidopsis.
A pilot-scale transposon mutagenesis experiment using a modified autonomous Activator (Ac) element, Ac delta Nael, was carried out in Arabidopsis thaliana. Four different transformants carrying Ac elements in different and defined genomic locations were used to generate 1000 plants carrying approximately 500 independent germinal transposition events. These plants were then selfed and the 1000 families screened in tissue culture and soil for phenotypic mutants. Fifty different families segregated mutations in their progeny. Preliminary Southern blot analysis of 29 families which segregated mutant progeny, showed that 28 had a transposed Ac. Six of the families were further tested for linkage between the transposed Ac and the mutant phenotype, and instability of the putatively tagged locus. Two of the mutants were shown to be tagged as they were tightly linked to a transposed Ac, and somatic and germinal reversion was associated with loss of Ac. One other mutant locus was shown to be closely linked to a transposed Ac, and therefore was likely to be tagged. The remaining three mutations were not tagged as they were not linked to a transposed Ac. In two of the tagged mutants Ac had transposed to closely linked sites, while in a third mutant the co-segregating Ac had transposed to a site which was not tightly linked to the donor T-DNA. Multiple insertions into the DIF1 locus were found, due to the preferential transposition of Ac to a linked site.
Arabidopsis↗
Physical map and organization of Arabidopsis thaliana chromosome 4.
A physical map of Arabidopsis thaliana chromosome 4 was constructed in yeast artificial chromosome clones and used to analyze the organization of the chromosome. Mapping of the nucleolar organizing region and the centromere integrated the physical and cytogenetic maps. Detailed comparison of physical with genetic distances showed that the frequency of recombination varied substantially, with relative hot and cold spots occurring along the whole chromosome. Eight repeated DNA sequence families were found in a complex arrangement across the centromeric region and nowhere else on the chromosome.
Arabidopsis↗
Differential inhibition of DNA synthesis by paracetamol in the rat testis and GI tract.
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Acetaminophen↗
A new theory of enterorecirculation of amino acids and its use for depleting unwanted amino acids using oral enzyme-artificial cells, as in removing phenylalanine in phenylketonuria.
Oral binders remove intestinal bile acid and prevent its reabsorption and recycling thereby lowering systemic cholesterol levels. The results in this paper demonstrate the presence of another extensive enterorecirculation for amino acids. Pancreatic and other glandular secretions into the intestine contain large amounts of proteins, enzymes and polypeptides. Tryptic digestion converts these into amino acids which are then reabsorbed back into the body as they pass down the intestine. This paper shows that this forms a large enterorecirculation of amino acids between the body and intestine. The dietary protein source of amino acids is negligible when compared to the endogenous source, since this paper shows that protein-free diet did not alter the intestinal amino acid concentration. This raises the possibility of using this for the selective depletion of specific body amino acids. In this paper we use a phenylketonuria (PKU) model in rats to test the use of this hypothesis. In PKU rats, artificial cells microencapsulated phenylalanine ammonia lyase (PAL) given orally is more effective than a phenylalanine-free diet. The enzyme artificial cells are more efficient in lowering PHE in the intestine, plasma and cerebrospinal fluid. Compared to PKU on PHE-free diet, this has resulted in better weight gain and general physical condition. Preliminary studies also show that artificial cells microencapsulated asparaginase, glutaminase and tyrosinase given orally can deplete the corresponding amino acid from the intestine.
Amino Acids↗
Integration of CAPS markers into the RFLP map generated using recombinant inbred lines of Arabidopsis thaliana.
Konieczny and Ausubel have described a technique whereby Arabidopsis thaliana loci can be rapidly mapped to one of the ten chromosome arms using a small number of F2 progeny from crosses between the ecotypes Landsberg erecta and Columbia. The technique involves the use of 18 co-dominant, cleaved amplified polymorphic sequence (CAPS) markers which are evenly distributed throughout the Arabidopsis genome. We have mapped these 18 markers using recombinant inbred (RI) lines generated in our laboratory. These data enable a better integration of loci mapped relative to the CAPS markers into the restriction fragment length polymorphism (RFLP) map generated using Arabidopsis RI lines.
Arabidopsis↗
Hospital administrative costs.
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Hospital Administration↗
Transposon-induced inversion in Antirrhinum modifies nivea gene expression to give a novel flower color pattern under the control of cycloidearadialis.
The nivea (niv) gene of Antirrhinum majus encodes chalcone synthase, an enzyme involved in synthesis of anthocyanin pigments. The nivrec:98 allele contains a single copy of the transposon Tam3 inserted at the niv locus. A large chromosomal rearrangement derived from this mutant has been shown to be flanked by two copies of Tam3. In this study, we compared sequences involved in this rearrangement with their progenitor sequences and concluded that the rearrangement is an inversion resulting from an aberrant transposition occurring shortly after replication of Tam3 that left both copies of Tam3 active after the rearrangement. Excision of Tam3 from its position adjacent to the niv coding region resulted in a novel distribution of anthocyanin pigment in the flower tube, caused by the interaction of the new sequences with the remnant of the niv promoter. The new sequences upstream of niv serve both to enhance niv transcription and to redirect the pattern of gene expression, placing niv under the control of the gene cycloidearadialis, which determines the morphogenetic polarity of the flower.
Alleles↗
A preclinical screening test for modified hemoglobin to bridge the gap between animal safety studies and use in human.
The infusion of large amount of modified hemoglobin as blood substitute can potentially result in hypersensitivity and anaphylactic reactions, antibody-antigen reactions and others. Animal safety studies are important. However, response in animals may not be the same as in human. Before injecting into human, we may need to use an in-vitro screening procedure. One approach is based on testing the effects of modified Hb on complement activation (C3a) of human plasma. This paper describes this screening test. It also discusses how this may potentially be used. For instance using this to test for contamination from trace membrane fragments with blood group antigen or lipids, antibody-antigen complexes, endotoxin, trace fragments of microorganisms, residual amounts of some polymers, emulsifying agents, and organic solvents. There is also the possibility of obtaining plasma from a very large human population and analyse each of these to study the epidemiology of adverse reactions in different groups and types of patients.
Anaphylaxis↗
Immunological effects of hemoglobin, encapsulated hemoglobin, polyhemoglobin and conjugated hemoglobin using different immunization schedules.
Repeated subcutaneous immunizing injections into rats of Freund's adjuvant containing rat hemoglobin or o-raffinose rat polyhemoglobin did not result in increase in IgG antibody titers. However, heterologous hemoglobin injected as above is antigenic (49.50 + 6.70 % CPM). Crosslinking heterologous hemoglobin into o-raffinose polyhemoglobin further increased its antigenicity (75.60 + 4.08). Thus, unlike homologous hemoglobin, cross-linking of heterologous hemoglobin increased its antigenicity. Liposome encapsulated homologous hemoglobin injected subcutaneously with or without Freund's adjuvant did not show antigenicity. Encapsulated heterologous hemoglobin resulted in a minimal increase in antibody titers (10.73 + 4.64) only with Freund's adjuvant, but no increase when injected without Freund's adjuvant. Conjugated heterologous hemoglobin (PEG-Hb) injected intravenously by itself at weekly intervals did not result in significant increase in antibody titers on the 5th week.
Animals↗
Development of an efficient transposon tagging system in Arabidopsis thaliana.
We are currently developing a transposon tagging system in Arabidopsis thaliana using the maize transposable elements Ac and Ds. In order to make the system as efficient as possible, four different antibiotic resistance markers have been tested for their usefulness in monitoring excision and reinsertion of transposons in the Arabidopsis genome. Owing to the low transposition frequency of wild-type Ac in Arabidopsis we have also tested a number of modifications to the Ac element. Deletion of the CpG-rich region in the transposase 5' untranslated leader was found to significantly increase the activity of Ac in Arabidopsis. In our first non-targeted tagging experiment, 200 individuals with an inherited transposed Ac element have been collected and their progeny are being screened in families of twelve for segregation of mutant phenotypes. A two-element system, using Ac and Ds, is also being developed and a way of stabilising the Ds-induced mutations by counter selecting plants carrying the transposase source is being investigated. The Agrobacterium T-DNA insertions carrying the different transposons are currently being mapped onto the Arabidopsis RFLP map. Inverse polymerase chain reaction (IPCR) is being used to generate flanking DNA probes, that will be used on the RFLP blots to map the T-DNA relative to the other known markers. Once the first few have been mapped the first targeted tagging experiment will be initiated.
Arabidopsis↗