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D J Llewellyn

Publications and source records attributed to D J Llewellyn.

7 recordsLinked to original sources
PubMed1990

Nonlegume hemoglobin genes retain organ-specific expression in heterologous transgenic plants.

Hemoglobin genes from the nitrogen-fixing nonlegume Parasponia andersonii and the related non-nitrogen-fixing nonlegume Trema tomentosa have been isolated [Landsmann et al. (1986). Nature 324, 166-168; Bogusz et al. (1988). Nature 331, 178-180]. The promoters of these genes have been linked to a beta-glucuronidase reporter gene and introduced into both the nonlegume Nicotiana tabacum and the legume Lotus corniculatus. Both promoters directed root-specific expression in transgenic tobacco. When transgenic Lotus plants were nodulated by Rhizobium loti, both promoter constructs showed a high level of nodule-specific expression confined to the central bacteroid-containing portion of the nodule corresponding to the expression seen for the endogenous Lotus leghemoglobin gene. The T. tomentosa promoter was also expressed at a low level in the vascular tissue of the Lotus roots. The hemoglobin promoters from both nonlegumes, including the non-nodulating species, must contain conserved cis-acting DNA signals that are responsible for nodule-specific expression in legumes. We have identified sequence motifs postulated previously as the nodule-specific regulatory elements of the soybean leghemoglobin genes [Stougaard et al. (1987). EMBO J. 6, 3565-3569].

Base Sequence↗
PubMed1990

OCSBF-1, a maize ocs enhancer binding factor: isolation and expression during development.

The ocs-elements comprise a family of related 20-base pair DNA sequences with dyad symmetry that are functional components of the promoters of several genes introduced into the plant nucleus by Agrobacterium transformation or infection by DNA viruses. We describe the isolation and characterization of a maize cDNA that encodes a protein, OCSBF-1, that binds specifically to ocs-element sequences. The 21-kilodalton OCSBF-1 protein was encoded by a single copy, intron-less gene. The gene was differentially expressed in maize plants. Developing leaves had a gradient of OCSBF-1 mRNA with the basal portion of the leaves, which contain dividing and differentiating cells, having 40-fold to 50-fold higher levels of OCSBF-1 transcripts than the apical portion of the leaves, where the cells are fully differentiated. Roots and shoots of young plants had levels of OCSBF-1 mRNA similar to the basal portions of developing leaves. OCSBF-1 contained a small basic amino acid region and a potential leucine zipper motif homologous to the DNA-binding domains of the basic region-leucine zipper family of transcription factors such as Jun and GCN4. A truncated protein with the amino-terminal 76 amino acids of OCSBF-1, encompassing the basic domain and leucine zipper motif, still bound to ocs-element sequences in vitro. OCSBF-1 was able to bind to a site within each half of the ocs-element as well as to animal AP-1 and CREB sites.

Amino Acid Sequence↗
PubMed1989

The ocs-element is a component of the promoters of several T-DNA and plant viral genes.

The ocs-element is an enhancer element first identified in the promoter of the octopine synthase gene (OCS) where it occurs as a 16 bp palindromic sequence. The transcriptional enhancing activity of the ocs-element correlated with in vitro binding of a transcription factor. We have now identified ocs-elements in the promoter regions of six other T-DNA genes involved in opine synthesis and three plant viral promoters including the 35S promoter of cauliflower mosaic virus. These elements bind the ocs transcription factor in vitro and enhance transcription in plant cells. Comparison of the sequences of these 10 elements has defined a 20 bp consensus sequence, TGACG(T/C)AAG(C/G)(G/A)(A/C)T(G/T)ACG(T/C)(A/C)(A/C), which includes the 16 bp palindrome in its central region. We propose the name ocs-element for this class of promoter elements of similar sequence and function.

Base Sequence↗
PubMed1989

Expression of a bacterial gene in transgenic tobacco plants confers resistance to the herbicide 2,4-dichlorophenoxyacetic acid.

Plants resistant to the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) were produced through the genetic engineering of a novel detoxification pathway into the cells of a species normally sensitive to 2,4-D. We cloned the gene for 2,4-D monooxygenase, the first enzyme in the plasmid-encoded 2,4-D degradative pathway of the bacterium Alcaligenes eutrophus, into a cauliflower mosaic virus 35S promoter expression vector and introduced it into tobacco plants by Agrobacterium-mediated transformation. Transgenic tobacco plants expressing the highest levels of the monooxygenase enzyme exhibited increased tolerance to 2,4-D in leaf disc and seed germination assays, and young plants survived spraying with levels of herbicide up to eight times the usual field application rate. The introduction of the gene for 2,4-D monooxygenase into broad-leaved crop plants, such as cotton, should eventually allow 2,4-D to be used as an inexpensive post-emergence herbicide on economically important dicot crops.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1987

Structure and expression of an alcohol dehydrogenase 1 gene from Pisum sativum (cv. "Greenfeast").

Three genomic clones for anaerobically inducible alcohol dehydrogenase (Adh) have been isolated from Pisum sativum cv. "Greenfeast" via cDNA cloning. One of these contains a complete gene, has exon sequences corresponding to one of the cDNA sequences and is likely to be an expressed gene. This gene has a structure similar to the Adh genes of maize, with introns in the same positions in the coding sequence but differing in their lengths and nucleotide sequences. At the nucleotide level the coding sequence is 75% homologous to both maize Adh1 and Adh2 and 80% homologous to the Adh gene from Arabidopsis, but has an extra coding triplet in exon 1 that is not found in the other plant Adh genes. The non-translated regions of all the gene transcripts are widely divergent between species. A short segment of the pea Adh promoter region (-290 to +57) was fused to a reporter gene and introduced into protoplasts of Nicotiana plumbaginifolia by electroporation. Transient expression of the introduced gene increased markedly when the transfected protoplasts were incubated under anaerobic conditions, showing that cis-acting regulatory signals necessary for anaerobic control of expression reside in the -290 to +57 segment. Sequence comparisons between this region and the corresponding regions of maize and Arabidopsis Adh genes have identified short sequences that may be involved in the anaerobic regulation of plant Adh genes.

Alcohol Oxidoreductases↗