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Biomedical subjects

A Spena

Publications and source records attributed to A Spena.

At least 19 recordsLinked to original sources
PubMed2000

The spliceosomal intron of the rolA gene of agrobacterium rhizogenes is a prokaryotic promoter.

Agrobacterium rhizogenes transfers DNA (T-DNA) from its Ri plasmid to plant cells. All T-DNA genes are expressed in plant cells. The rolA gene is the only T-DNA gene that contains an intron in the untranslated leader region of its mRNA. This paper shows that (i) the rolA gene is also transcribed in bacteria; (ii) the 85 bp corresponding to the spliceosomal intron drives prokaryotic gene expression in agrobacteria, in free-living rhizobia and in bacteroids within root nodules; and (iii) promoter activity is abolished by the deletion of 63 bp from its 5' end and is reduced by mutations changing its sequence near the putative -10 region. The expression pattern of a chimeric reporter gene shows that, in free-living bacteria, gene expression takes place during the exponential phase of growth and increases at the onset of the stationary phase. Within root nodules, reporter gene expression occurs in the invasion, nitrogen fixing and senescent zones.

Bacterial Proteins↗
PubMed1997

Mutational analysis of the rolA gene of Agrobacterium rhizogenes in tobacco: function of the rolA pre-mRNA intron and rolA proteins defective in their biological activity.

The rolA gene of Agrobacterium rhizogenes contains in its untranslated leader region a spliceosomal intron, which is spliced in Arabidopsis and in Nicotiana tabacum. Expression under the control of the 35S promoter from cauliflower mosaic virus of a rolA gene derivative defective in splicing still causes alterations of growth in transgenic tobacco plants. Splicing of rolA mRNA is required for efficient expression of the rolA phenotype in vivo. Moreover, splicing is required for efficient in vitro translation of the rolA mRNA. In contrast, expression of a 35S-rolA gene derivative with the ATG initiation codon replaced by ATA does not cause any phenotypical alteration. Mutations leading to amino acid substitutions at positions 37 and 40 of the rolA coding region were isolated as null mutants in Arabidopsis plants transgenic for the rolA gene. However, when expressed in tobacco under the control of the 35S promoter, they cause a rolA phenotype reduced in the expressivity of its traits. The molecular characterization of rolA mutants might be useful for understanding the biochemical function of the rolA protein.

Bacterial Proteins↗
PubMed1997

Genetic engineering of parthenocarpic plants.

Transgenic tobacco and eggplants expressing the coding region of the iaaM gene from Pseudomonas syringae pv. savastanoi, under the control of the regulatory sequences of the ovule-specific DefH9 gene from Antirrhinum majus, showed parthenocarpic fruit development. Expression of the DefH9-iaaM chimeric transgene occurs during flower development in both tobacco and eggplant. Seedless fruits were produced by emasculated flowers. When pollinated, the parthenocarpic plants produced fruits containing seeds. In eggplant, the genetic manipulation allowed fruit set and growth under environmental conditions prohibitive for fruit setting in the untransformed line, which did not set fruit at all. Under normal environmental conditions, production of marketable fruits took place from pollinated and unpollinated transgenic flowers, while flowers of untransformed control plants did produce fruits of marketable size only from fertilized flowers.

Chimera↗
PubMed1995

Low molecular weight peptide from calf's liver mitochondrial DNA: structure and effect on DNA as a template.

A peptide fraction from the mitochondrial DNA of calf's liver was isolated using Drouin's method (1). This peptide fraction, which was extracted at pH 9.5 from an extensively purified mitochondrial DNA (2), has been shown to exert an in vitro regulatory role on the transcription and duplication activity of DNA (3). The same fraction also binds with mitochondrial DNA with a high affinity constant and stabilizes DNA from calf's thymus against thermal denaturation. The peptides from mitochondrial DNA have been subfractionated by fingerprinting-like techniques and one of them has been sequenced.

Amino Acid Sequence↗
PubMed1994

Splicing of the rolA transcript of Agrobacterium rhizogenes in Arabidopsis.

The rolA gene encoded on the Ri plasmid A4 of Agrobacterium rhizogenes is one of the transferred (TL-DNA) genes involved in the pathogenesis of hairy-root disease in plants. The function of the 100-amino acid protein product of rolA is unknown, although its expression causes physiological and developmental alterations in transgenic plants. The rolA gene of A. rhizogenes contains an intron in its untranslated leader region that has features typical of plant pre-messenger RNA introns. Transcription and splicing of the rolA pre-messenger RNA occur in the plant cell.

Arabidopsis↗
PubMed1994

Amino acid composition of two peptides purified from mitochondrial calf liver DNA.

In this research the amino acidic composition of a peptide fraction from mitochondrial DNA has been determined, using HPLC and the fingerprinting technique. This peptide fraction has been shown to be composed of two sub-fractions with different reactivity to ninhydrin, and thus supplied with several N-substitute groups. The composition of the first fraction is Gln, Glu, Pro, Leu. The second fraction composition is Pro, Glu or Gln, Asp or Asn, Ser.

Amino Acid Sequence↗
PubMed1993

Genes involved in the control of growth and differentiation in plants.

The mechanisms underlying totipotency, the unique ability of isolated plant cells to regenerate into plants, offer developmental biology a unique challenge. While it has been recognised for some time that phytohormones, such as auxin and cytokinin, play a role in this process by inducing a variety of growth patterns in both isolated cells, unorganised callus and intact plants, the molecular basis of their action remains unknown. The molecular and biochemical analysis of the novel interaction between tumour-inducing soil bacteria and the wounded plant has provided a valuable insight into how plants respond to phytohormones. During tumour formation, the bacteria transfer to the genome of the host plant a variety of genes which either short circuit the normal pathways of accumulation of phytohormones or modify how the plant cell responds to them. In parallel to these studies, we have been investigating plant genes involved directly or indirectly in the mechanism of phytohormone action. Auxin-binding proteins (putative receptors) have been localised in various cellular locations and the genes encoding them are currently undergoing analysis. Recently, a novel form of T-DNA has been devised by which mutant plant cell lines can be generated which grow in culture in the absence of exogenously applied auxin. The tagged genes, which are in effect plant cellular proto-oncogenes, are likely to shed more light on how auxin serves to regulate growth and development.

Cell Differentiation↗
PubMed1993

NTGLO: a tobacco homologue of the GLOBOSA floral homeotic gene of Antirrhinum majus: cDNA sequence and expression pattern.

We report the cloning and DNA sequence of a cDNA from Nicotiana tabacum, NTGLO, as well as the pattern of expression of the NTGLO gene in wild-type tobacco plants. The NTGLO cDNA encodes a protein of 209 amino acids, which shows 73% identity with the GLO protein encoded by the GLO gene of Antirrhinum majus, a homeotic gene involved in the genetic control of flower development. Northern blot analysis shows that the NTGLO gene is expressed mainly in floral organs and, within the flower, expression is restricted to petals and stamens. The NTGLO gene most probably represents a true homologue of the GLO gene because: i) the MADS boxes, of the two genes are highly homologous (56 out of 58 amino acids are identical): ii) at the carboxy-terminal a block of 19 amino acids is perfectly conserved between the NTGLO and GLO proteins and iii) their expression patterns in floral organs are identical.

Amino Acid Sequence↗
PubMed1993

Floral development and expression of floral homeotic genes are influenced by cytokinins.

Tobacco plants that are somatic mosaics for the expression of a cytokinin-synthesizing gene have viviparous leaves. Epiphyllous buds can be either vegetative or floral. Floral adventitious buds can be either normal or abnormal. Abnormalities of floral development correlate with: (i) a local activation of the cytokinin-synthesizing gene, (ii) a drastic increase in floral cytokinin content, and (iii) a decrease in the steady-state levels of mRNA homologous of the homeotic genes DEFA, GLO and PLENA of Antirrhinum majus. Thus, these data show in planta that cytokinins, a class of phytohormones, are able to alter the development of floral organs and to decrease the expression of three homeotic floral genes.

Base Sequence↗
PubMed1993

Effect of a peptide fraction extracted from mitochondrial DNA on rat liver cell viability.

The authors verified the effect of a peptidic fraction from mitochondrial DNA on liver cell cultures. Primary cultures treated with the mitochondrial peptidic fraction (final concentration 0.025 O.D./ml) showed a higher viability after 48 hours with respect to cultures without mitochondrial peptidic fraction (p < 0.05). The results indicate a probable action of the mitochondrial peptidic fraction on liver cell viability.

Animals↗
PubMed1992

Effect of thyroid hormones and their analogues on the mitochondrial calcium transport activity.

In this paper the authors studied the effects of thyroid hormones and their structural analogues on the mitochondrial calcium transport activities. The thyroid hormones, 3,5,3' L-triiodothyronine (LT3) and 3,5,3'5' L-tetraiodothyronine (LT4) at physiological intracellular concentrations between 7.2 and 9 nM, decouple total Ca++ transport, as well as inhibit the passive transport of Ca++, either due to oxidation of pyruvate, malate or succinate or after inhibition with rotenone. The optical isomers 3,5,3' D-triiodothyronine (DT3) and 3,5,3',5' D-tetraiodothyronine (DT4) are less effective at all the used concentrations. Furthermore the structural analogues 3,3',5' L-triiodothyronine (LrT3), 3,5-dicloro, 3',5' L-diiodothyronine (LDiClT2) and 3,5 L-diiodothyronine (LT2) furnished even less effects on the same activities. The effect of the thyroid hormones and of their structural analogues has revealed that the mitochondrial calcium transport may be influenced both by a stereospecific interaction between hormones and protein ligands and by a lipophilic chaotropic action on the mitochondrial membranes lipids. In this context it is interesting to consider that both thyroid hormones and Ca++ transport activity are interacting with the energetic metabolism by means of phosphorylation and substrate oxidation mechanism.

Animals↗
PubMed1991

The protein encoded by the rolB plant oncogene hydrolyses indole glucosides.

The rolB gene of Agrobacterium rhizogenes, whose expression stimulates the formation of roots by transformed plant tissues and other growth alterations in transgenic plants, codes for a beta-glucosidase able to hydrolyse indole-beta-glucosides. Indeed, we show that extracts of bacteria and/or plant tissue expressing the rolB protein hydrolyse indoxyl-beta-glucoside (plant indican). Because of the structural similarity between indoxyl-beta-glucoside and indole-3-acetyl-beta-glucoside (IAA-beta-glucoside), we propose that the physiological and developmental alterations in transgenic plants expressing the rolB gene could be the result of an increased intracellular auxin activity caused by the release of active auxins from inactive beta-glucosides. Thus two of the oncogenes carried by the T-DNA of the plant pathogen Agrobacterium rhizogenes (rolB and rolC) perturb plant growth and development by coding for beta-glucosidases with distinct specificities. Whereas the rolC beta-glucosidase releases cytokinins from their glucoside conjugates, the rolB encoded protein hydrolyses indole-beta-glucosides. The combined action of these two genes therefore is expected to modulate the intracellular concentration of two of the main growth factors active in plants.

Base Sequence↗
PubMed1991

The plant oncogene rolC is responsible for the release of cytokinins from glucoside conjugates.

The rolC gene of Agrobacterium rhizogenes, which drastically affects growth and development of transgenic plants, codes for a cytokinin-beta-glucosidase. Indeed, rolC protein expressed in Escherichia coli as a fusion protein hydrolyses cytokinin glucosides, thus liberating free cytokinins. Furthermore, beta-glucosidase activity present in E. coli extracts expressing the rolC protein was inhibited by affinity-purified antibodies specific for the rolC protein. Finally, rolC proteins expressed in transgenic plants were shown to be responsible for cytokinin-beta-glucosidase activity. Morphological and phytohormonal analysis, performed on transgenic plants that are somatic mosaics for the expression of the rolC gene, extend and confirm our interpretation that the developmental, physiological and morphological alterations caused by rolC expression in transgenic plants are primarily due to a modification of the cytokinin balance. These observations shed new light on the control of growth and differentiation in plants by growth factors.

Bacterial Proteins↗
PubMed1991

Cytosolic localization in transgenic plants of the rolC peptide from Agrobacterium rhizogenes.

The rolC gene of Agrobacterium rhizogenes codes for a peptide with an apparent molecular weight of approximately 20 kDa. Immunolocalization of the rolC peptide, in leaves of transgenic plants which are genetic mosaics for the expression of the rolC gene, is restricted to the phenotypically altered sectors. Subcellular fractionation of homogenates from 35S-rolC transgenic leaves shows the cytosolic localization of the rolC peptide.

Animals↗