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Biomedical subjects

A Spena

Publications and source records attributed to A Spena.

At least 37 records · Page 2Linked to original sources
PubMed1991

The indoleacetic acid-lysine synthetase gene of Pseudomonas syringae subsp. savastanoi induces developmental alterations in transgenic tobacco and potato plants.

The iaaL gene of Pseudomonas syringae subsp. savastanoi encodes an indoleacetic acid-lysine synthetase that conjugates lysine to indoleacetic acid. A chimaeric gene consisting of the iaaL coding region under the control of the 35S RNA promoter from cauliflower mosaic virus (35SiaaL) has been used to test if iaaL gene expression leads to morphological alterations in tobacco and potato. Transgenic tobacco plantlets bearing this construct have been shown to synthesize IAA-[14C]lysine when fed with [14C]lysine. In late stages of development, their leaves show an increased nastic curvature (epinasty) of the petiole and midvein, a finding suggestive of an abnormal auxin metabolism. The alteration is transmitted to progeny as a dominant Mendelian trait cosegregating with the kanamycin resistance marker. Transgenic potato plants harbouring the construct are also characterized by petiole epinasty. Moreover, 35SiaaL transgenic plants have an increased internode length in potato and decreased root growth in both tobacco and potato. An increased content of IAA-conjugates in leaf blade was found to correlate with the epinastic alterations caused by iaaL gene expression in tobacco leaves. These data provide evidence that IAA conjugation is able to modulate hormone action, suggesting that the widespread endogenous auxin-conjugating activities are of physiological importance.

Chromatography, High Pressure Liquid↗
PubMed1991

Single rol Genes from the Agrobacterium rhizogenes T(L)-DNA Alter Some of the Cellular Responses to Auxin in Nicotiana tabacum.

Two kinds of cellular responses to auxin, the hyperpolarization of protoplasts and the division of protoplast-derived cells, were compared in Nicotiana tabacum plants transformed by different T-DNA fragments of Agrobacterium rhizogenes strain A4. Using transmembrane potential difference measurements to characterize hormonal sensitivity of mesophyll protoplasts, we found a 30-fold increase in sensitivity to auxin in protoplasts transformed by the whole Ri A4 T-DNA. Furthermore, the rol genes of the Ri A4 T(L)-DNA, together or as single genes, were able to increase the sensitivity to auxin by factors up to 10(4). The different effects of the single rol genes on the sensitivity of mesophyll protoplasts to auxin, rolB being the most powerful, were consistent with their respective rhizogenic effects on leaf fragments (A Spena, T Schmülling, C Koncz, J Schell [1987] EMBO J 6: 3891-3899). No difference was seen concerning the effects of auxin on division of cells derived from normal or transformed protoplasts. These results suggest that only some cellular responses to auxin could be selectively altered by rol genes. They also show that rol-transformed tobaccos can be a model system to study auxin action in plants.

Journal Article↗
PubMed1990

Unstable liaisons: the use of transposons in plant genetic engineering.

Transposable elements can be used to activate gene expression in clonal populations of cells and consequently to generate genetic mosaics. Plant mosaics, having organs composed of intermixed tissues with wild-type and mutant appearance, can be used to evaluate whether the action of a morphogenetic gene is cell-autonomous. Transposon-split gene constructions could also be used to raise plants transgenic for lethal genes and, in more general terms, they could be an ancillary tool in several types of biological experiment.

DNA Transposable Elements↗
PubMed1989

Cell-autonomous behavior of the rolC gene of Agrobacterium rhizogenes during leaf development: a visual assay for transposon excision in transgenic plants.

We describe a genetic switch based on the Ac transposable element of maize and the rolC gene of Agrobacterium rhizogenes, a dominant gene, which has pleiotropic effects on plant growth and morphology. Moreover, rolC gene expression under the control of the 35S cauliflower mosaic virus promoter decreases chlorophyll content in transgenic tobacco plants. Chlorophyll is a visible cell-autonomous marker, and it is shown here that the reduction in chlorophyll content caused by the rolC gene product allows us to monitor, in palisade or spongy mesophyll cells, Ac excision events resulting in rolC gene expression as pale-green sectors and spots. Our results indicate that the rolC gene product behaves in a cell-autonomous manner during leaf development, at least as far as chlorophyll accumulation is concerned. In addition, the rolC gene can be useful to evaluate visually if and when a transposable element is active. Most important, we propose the use of a transposable element as a tool to activate expression of morphogenetic genes in a clonal population of cells. This could be particularly useful when studying genes affecting growth and development whose constitutive expression can severely impair regeneration of transgenic plants.

Brassica↗
PubMed1989

Promoters of the rolA, B, and C genes of Agrobacterium rhizogenesare differentially regulated in transgenic plants.

Chimeric genes containing the beta-glucuronidase reporter gene under the control of the rolA, B, and C promoters of Agrobacterium rhizogenes are expressed in a regulated manner in transgenic plants. The intergenic region separating the rolB and C genes represents a bidirectional promoter. This bidirectional promoter regulates transcription for both genes in a similar fashion in aerial organs of the plants, but in a distinct way in roots. Moreover, both rolB and C promoter activities differ from those characteristic of the rolA promoter. Thus, promoters of bacterial origin show differential expression in transgenic plants, and regulation of roI gene expression plays a role in the biological effects caused by the rolA, B, and C genes.

Culture Techniques↗
PubMed1988

Single genes from Agrobacterium rhizogenes influence plant development.

The combined expression of the rol A, B, and C loci of Agrobacterium rhizogenes Ri-plasmids establishes, in transgenic tobacco plants, a pathological state called hairy-root syndrome. However, when expressed separately they provoke distinct developmental abnormalities characteristic for each rol gene. Moreover, changes in their mode of expression obtained by replacing the promoters of the rol B and C genes with the cauliflower mosaic virus 35S promoter elicit new and distinct developmental patterns. These results indicate that the different rol gene products have either different targets, or have a qualitatively different effect on the same target. The target(s) must be involved in the control of plant development. Although each of the three rol genes are independently able to promote root formation in tobacco, efficient root initiation and growth is best achieved through the combined activities of more than a single rol gene. Models explaining the biological effects of A. rhizogenes-derived TL-DNA genes are discussed.

Bacterial Proteins↗
PubMed1987

Independent and synergistic activity of rol A, B and C loci in stimulating abnormal growth in plants.

The Ri plasmid A4 of Agrobacterium rhizogenes contains within its T-DNA genetic information able to trigger root formation in infected plants. Tobacco plants regenerated from transformed roots display the hairy root (hr) syndrome. We show that DNA fragments containing the rol B locus alone are able to induce root formation both in tobacco and kalanchoe tissues. The rol A and the rol C loci by themselves are also able to induce root formation in tobacco but not in kalanchoe. This capacity to induce root formation in either host is greatly increased when the rol A and/or C loci are combined with the rol B locus. Root induction is shown to be correlated with the expression of the rol loci. Transgenic plants exhibit all the characteristics of the hairy root syndrome only when all three loci are present and expressed. Although the activity of the rol encoded functions is synergistic, each of them appears to independently influence host functions involved in the determination of root differentiation.

Journal Article↗
PubMed1985

Translation efficiency of zein mRNA is reduced by hybrid formation between the 5'- and 3'-untranslated region.

The secondary structure of zein mRNA affects its translation potential. Here we show that in a cell-free system the translation efficiency of zein mRNA containing inverted repeats in the 5'- and 3'-untranslated regions is reduced. This translational block is released after deletion of the 3'-inverted repeat. We conclude that the translational block is caused by hybrid formation between the two inverted repeats. The translational efficiency of zein mRNAs, is also affected by varying the length or the primary structure of the 5'-untranslated region.

3' Untranslated Regions↗
PubMed1983

Two adjacent genomic zein sequences: structure, organization and tissue-specific restriction pattern.

A clone isolated from a library of genomic clones from Zea mays contains two adjacent zein light-chain genes. The nucleotide sequence of the two coding regions and their flanking sequences shows that the two genes represent two different subclasses of light-chain zeins. One belongs to an abundant and highly conserved class and the other, which is 88% homologous to the first, is less represented in the genome of maize line W64A. Both genes present in clone zE are anomalous: one contains a mutation that introduces a termination codon after 39 amino acids, the other has the ATG initiation codon mutated to CTG. The presence of inversions, insertions and short inverted or direct repeats in the flanking sequences suggests that zein genes may be subject to rearrangements and transpositions. Southern blot analysis of genomic DNA indicates that the particular arrangement represented by clone zE is present at least four times in maize line W64A but other arrangements are found in this and other maize lines. DNA extracted from different tissues and developmental stages is digested differently by enzymes sensitive to methylation of their target sequence. The results indicate that zein genes contain methylated sites that are demethylated in correlation with their expression.

Base Sequence↗
PubMed1983

[Echographic study of the inferior vena cava in abdominal neoplastic pathology. Comparison with the inferior cavography].

The authors evaluated the reliability of echography in the involvement of the inferior vena cava in the abdominal tumors. 137 patients were studied with echography and 125 with inferior cavography too. All the diagnosis were confirmed with arteriography and/or CT and/or surgical findings. The reliability of the echographic method was significant, and particularly in case of emboli and tumor invasion.

Abdominal Neoplasms↗
PubMed1982

A homologous repetitive block structure underlies the heterogeneity of heavy and light chain zein genes.

Heavy and light chain zein genes from maize, affected by different regulatory loci, are related in sequence and structure. The two kinds of genes code for a signal peptide, a head region of 67 amino acids, six and a half to eight repetitive blocks of 20 amino acids each and a short tail piece. This block structure would allow inter or intragenic recombination giving rise to heterogeneous zein genes. Length variation in zein polypeptides is also due to the occurrence of termination mutations within some genes. Homology between heavy and light chain zein genes extends to the flanking sequences where a short region at the 5' end of the transcript can base pair with the 3' end and may have regulatory implications.

Journal Article↗
PubMed1982

[Ultrasound in the diagnosis of Wilms' tumor].

Ultrasound (US) play a very important role in the diagnosis of Wilms' tumour. The authors analyze the findings in 12 children affected by this neoplasia. The resolution power of 4 different diagnostic levels is also analyzed. They are: a) mass identification; b) diagnosis of the tumour nature; c) diffusion balance; d) recurrence control. The most relevant resolution power lies in the diagnosis of nature and in the recurrence control.

Child↗