Chromatin and Arabidopsis root development

During development cells transit through different states as they pass from stem cell to terminally differentiated cell. There is evidence that the transition from one state to another can be accompanied by changes in epigenetic state of genes, which is embodied in chromatin state. Here we give an overview of the changes in chromatin that accompany the regulation of expression and review the evidence for the involvement of such changes during epidermal root development and discuss the roles that these changes play in the differentiation of the cell types involved.     

Alcohol dehydrogenase isozymes of Triticum: Dissociation and recombination of subunits

Summary Conditions have been defined for the dissociation of active forms of Triticum alcohol dehydrogenase (alcohol: NAD oxidoreductase, E.C. 1.1.1.1) into monomers and for the reassociation of the subunits into active enzymes. Results of experiments in which the subunits of genetically controlled electrophoretic variants of alcohol dehydrogenase were dissociated and recombined in crude tissue extracts support the hypothesis that the enzyme exists functionally as a dimer in Triticum.     

Intragenic recombination in the CSR1 locus of Arabidopsis

Four classes of herbicides are known to inhibit plant acetolactate synthase (ALS). In Arabidopsis, ALS is encoded by a single gene, CSR1. The dominant csr1-1 allele encodes an ALS resistant to chlorsulfuron and triazolopyrimidine sulfonamide while the dominant csr1-2 allele encodes an ALS resistant to imazapyr and pyrimidyl-oxy-benzoate. The molecular distance between the point mutations in csr1-1 and csr1-2 is 1369 bp. Here we used multiherbicide resistance as a stringent selection to measure the intragenic recombination frequency between these two point mutations. We found this frequency to be 0.008 ± 0.0028. The recombinant multiherbicide-resistant allele, csr1-4, provides an ideal marker for plant genetic transformation.     

Sequence analysis of two null-mutant alleles of the single Arabidopsis Adh locus

Summary Data presented in this paper deal with a further molecular characterization of 2 out of 32 EMS-induced Arabidopsis ADH null mutants that we isolated previously. In order to localize and characterize each mutation at the molecular level, we have cloned and completely sequenced the R002 and R006 null mutant alleles. For mutant R002, which does not contain any detectable levels of ADH protein and mRNA, we have found that the mutation is due to a single C to T base pair substitution in the reading frame; this leads to the incorporation of a TAG stop codon (amber nonsense mutation). For mutant R006, which contains normal levels of inactive protein and mRNA levels, we found a G to A base pair transition. This gives rise to a Cys to Tyr amino acid substitution in the active site of the ADH enzyme.Abbreviations CRM cross-reacting material - 2,4-D 2,4-dichlorophenoxyacetic acid - EMS ethylmethanesulfonate     

Transposon-associated somatic gai-loss sectors in Arabidopsis

The gai mutation of Arabidopsis confers reduced gibberellin responses, and is inherited as a semidominant trait. Somatic sectors displaying wild-type phenotype were observed in plants which were heterozygous for gai and for a linked Ds element, and which also contained a source of the Ac transposase function. The frequency of these sectors was correlated with the level of transposase conferred by the transposase source, suggesting that the sectors are the result of transposon activity. The appearance of the sectors indicates that gai phenotype is restricted to cells containing a functional gai gene copy.     

The KEULE gene is involved in cytokinesis in Arabidopsis

 We present evidence to show that the KEULE gene of Arabidopsis is involved in cytokinesis. Mutant keule embryos have large multinucleate cells with gapped or incomplete cross walls, as well as cell wall stubs that are very similar to those observed upon caffeine inhibition of cytokinesis in plants. These defects are observed in all populations of dividing cells in the mutant, including calli, but less frequently in mature cells. Cell division appears to be slowed down, and the planes of cell division are often misoriented. In late embryos and seedlings, cross-wall formation usually appears complete, suggesting that the requirement for KEULE during cytokinesis is not absolute. Nonetheless, keule mutants die as seedlings with large polyploid cells. The bloated surface layer of keule seedlings does not uniformly behave like wild-type epidermis, and patches of this layer assume characteristics of the underlying ground tissue. The cytokinesis defect of keule mutants may influence aspects of cellular differentiation. Received: 24 April 1996 / Accepted: 11 June 1996     

Construction and characterization of the IGF Arabidopsis BAC library

A bacterial artificial chromosome (BAC) library has been established for Arabidopsis thaliana (ecotype Col-0) covering about seven haploid nuclear genome equivalents. This library, called the Institut für Genbiologische Forschung (IGF) BAC library, consists of 10 752 recombinant clones carrying inserts (generated by partial EcoRI digestion) of an average size of about 100 kb in a modified BAC vector, pBeloBAC-Kan. Hybridization with organellar DNA and nuclear repetitive DNA elements revealed the presence of 1.1% clones with mitochondrial DNA, 0.2% clones with plastid DNA, 3.2% clones with the 180 bp paracentromeric repeat, 1.6% clones with 5S rDNA, and 10.8% clones with the 18S-25S rDNA repeat. With its extensive genome coverage, its rather uniformly sized inserts (80 kb <85% <120 kb) and low contamination with organellar DNA, this library provides an excellent resource for A. thaliana genomic mapping, map-based gene cloning, and genome sequencing. Received: 26 November 1997 / Accepted: 19 February 1998     

Chitinase induction in onion tissue cultures

Chitinase activity in Allium cepa (onion) tissue cultures was investigated using a radioactive assay and polyacrylamide gel electrophoresis (PAGE). Increased chitinase activity was detected in callus cultured on agar-solidified media for 72 h with 1 mM salicylic acid or 0.05 M ethrel, and in callus cultured in liquid suspension for 72 h with 0.1 mM salicylic acid or 0.1 M ethrel. Non-denaturing PAGE analysis of callus suspension cultures treated with salicylic acid revealed a new chitinase activity which accumulated in the fluid of the suspension cultures.     

ISSR marker based analysis of micropropagated plantlets of Nothapodytes foetida

A DNA-based, inter simple sequence repeat (ISSR) markers were used to monitor genetic stability in micropropagated plantlets of Nothapodytes foetida. A total of 146 clear and distinct bands were produced using 26 primers resulting in 3 212 fragments. Out of 146, 135 bands (92.4 %) were monomorphic and 11 bands (7.53 %) were polymorphic which ranged from 200 to 21 226 bp in size. The number of bands per each primer varied from 1 to 11 with an average of 5.6 bands per primer. The banding pattern for each primer was uniform and comparable to mother plant from which the cultures had been established. The dendrogram based on the unweighted pair-group method with arithmetic averaging (UPGMA) depicted about 97 % homology between the mother plant and micropropagated plants. An attempt was made to reintroduce the micropropagated plants in the natural habitat and over 500 plants were successfully established.     

Storage and conversion of Eclipta alba synseeds and RAPD analysis of the converted plantlets

The encapsulated shoot tips and nodal segments of Eclipta alba were stored at 4, 12 and 20 °C under irradiance of 1.5 gmmol m⁻² s⁻¹ and high conversion was observed in synseeds stored at 4 °C for 8 weeks. Duration of storage was extended up to 12 weeks by decreasing sucrose concentration in the alginate matrix from 3 to 1 or 2 % and conversion frequency was 71.2–76.1 %. Synseed-derived plantlets survived by 100 % in ex vitro conditions. RAPD analysis revealed uniform amplification profile in donor and synseed derived plantlets.