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L Jouanin

Publications and source records attributed to L Jouanin.

50 records · Page 3Linked to original sources
PubMed1994

Enhancement of the endogenous cytokinin concentration in poplar by transformation with Agrobacterium T-DNA gene ipt.

The agrobacterial isopentenyltransferase (ipt) gene, under the control of its native promoter, was transferred to poplar (Populus tremula x P. alba) by an Agrobacterium co-cultivation method. The ipt-transformed stem explants developed calli that regenerated many buds in the absence of exogenous cytokinins. Microcuttings of the ipt transformants exhibited frequently branching shoots with short internodes that were unable to root. In this material, the concentrations of zeatin, zeatin riboside and isopentenyladenosine, determined by an indirect enzyme-linked immunosorbent assay (ELISA), were 4.8-. 17.1- and 14.6-fold higher, respectively, than in non-transformed shoots. Results are discussed with regard to cytokinin metabolism.

Journal Article↗
PubMed1993

Multiple regions of a divergent promoter control the expression of the Agrobacterium rhizogenes aux1 and aux2 plant oncogenes.

The two auxin biosynthesis genes, aux1 and aux2 of Agrobacterium rhizogenes strain A4, are located on opposite DNA strands with a short integenic region (394 bp) between their coding sequences. A functional analysis of this divergent promoter is presented. The transcription initiation sites of the two aux genes were determined and regions important for promoter activity were identified by deletion and transient expression analyses in tobacco protoplasts. The promoter activity of the aux intergenic region was demonstrated. A strong enhancer element contained within an 84 bp promoter fragment was identified. Far upstream regions were shown to have negative effects on the promoter activity of the short intergenic region. Interactions between positive elements in the intergenic region and negative effects of the upstream sequences may be the basis of strict control of the auxin biosynthesis necessary for the induction and maintenance of hairy root growth.

Base Sequence↗
PubMed1991

An alternative approach for gene transfer in trees using wild-type Agrobacterium strains.

Micropropagated shoots of three forest tree species, poplar (Populus tremula x P. alba), wild cherry (Prunus avium L.) and walnut (Juglans nigra x J. regia), were inoculated each with six different wild-type Agrobacterium strains. Poplar and wild cherry developed tumors that grew hormone-independently, whereas on walnut, gall formation was weak. On poplar and wild cherry, tumors induced by nopaline strains developed spontaneously shoots that had a normal phenotype and did not carry oncogenic T-DNA. From these observations, we have established a co-inoculation method to transform plants, using poplar as an experimental model. The method is based on inoculation of stem internodes with an Agrobacterium suspension containing both an oncogenic strain that induces shoot differentiation and a disarmed strain that provides the suitable genes in a binary vector. We used the vector pBI121 carrying neo (kanamycin resistance) and uidA (beta-glucuronidase) genes to facilitate early selection and screening. Poplar plants derived from kanamycin-resistant shoots that did not carry oncogenic T-DNA, were shown to contain and to express neo and uidA genes. These results suggest that wild-type Agrobacterium strains that induce shoot formation directly from tumors can be used as a general tool for gene transfer, avoiding difficult regeneration procedures.

Culture Techniques↗
PubMed1990

Identification of different agrobacterium strains isolated from the same forest nursery.

Several Agrobacterium strains isolated from the same forest nursery from 1982 to 1988 were compared by serological, biochemical, and DNA-DNA hybridization methods. Similarities among strains belonging to biovar 2 were observed by indirect immunofluorescence, whereas biovar 1 strains showed serological heterogeneity. Electrophoretic analysis of bacterial envelope-associated proteins showed that few bands appeared in the strains belonging to biovar 1, whereas many proteins appeared in the case of biovar 2 strains. Chromosomal DNA was analyzed with six random C58 chromosomal fragments. None of the six probes hybridized to the DNA of the two biovar 2 strains. One of the probes gave the same hybridization pattern with all biovar 1 strains, whereas the other probes yielded different patterns. The vir regions were closely related in the different pathogenic strains. The T-DNA and replication regions were less conserved and showed some variations among the strains.

Journal Article↗
PubMed1987

Expression vectors based on the Agrobacterium rhizogenes Ri plasmid transformation system.

This article describes several new expression vectors that capitalize on the ability of Agrobacterium rhizogenes to transfer DNA from its Ri plasmid to the plant nuclear genome. The intermediate vectors described include an expression cassette based on one of the three following promoters: the nopaline synthase promoter, or the cauliflower mosaic virus (CaMV) promoters responsible for transcription of either the 19S or 35S CaMV RNA. The termination and polyadenylation signals are either from the nopaline synthase gene or from CaMV. The expression micro-Ri plasmid described bears a selectable marker gene and an expression cassette cloned between the borders of the TL-region of the Ri plasmid of A. rhizogenes A4. Different strategies for using these vectors to introduce chimeric genes into plants are described, and the advantages and disadvantages of the two types of vectors are discussed.

Chromosomes, Bacterial↗
PubMed1986

Nucleotide sequence analysis of TL-DNA of Agrobacterium rhizogenes agropine type plasmid. Identification of open reading frames.

We have determined the nucleotide sequence of the Ri TL-DNA region from an Agrobacterium rhizogenes agropine-type plasmid using subcloned regions from the essentially identical Ri TL-DNAs from strains A4 and HRI. This sequenced region of 21,126 base pairs (bp) contains the complete TL-DNA region of the Ri plasmid as determined by analysis of TL-DNA borders in the genome of infected, clonal, Convolvulus arvensis plants. The left and right borders of the TL-DNA are flanked by 25-bp sequences which match the 25-bp terminal sequences found near the borders of T-DNA regions of Agrobacterium tumefaciens Ti plasmids. Other DNA sequences similar to these 25-bp terminal sequences are found within the TL region, and some of these sequences appear to be associated with Ri TL-DNA structures found in transformed tobacco plants. The TL-DNA region contains 18 open reading frames, many of which have 5' and 3' regulatory elements similar to those found in eukaryotic genes. In many cases, CCAAT and TATA elements were found upstream from putative transcriptional initiation codons, and poly(A) addition (AATAAA) elements were observed in presumed 3'-noncoding regions. Comparison of Ri TL-DNA coding and noncoding sequence regions with T-DNA sequence regions from octopine type Ti plasmid pTi15955 reveals no extensive sequence homologies.

Base Sequence↗
PubMed1986

Restriction maps and homologies of the three plasmids of Agrobacterium rhizogenes strain A4.

Agrobacterium rhizogenes strain A4 is a virulent agropine-type strain possessing three plasmids: plasmid a (pArA4a, 180 kb) is not necessary for plant transformation, plasmid b (250 kb) is the root-inducing plasmid (pRiA4), and plasmid c (pArA4c) is a cointegrate of pArA4a and pRiA4. The total plasmid DNA (pArA4) of strain A4 was cloned in the cosmid pHSG262 and the library obtained was used to establish BamHI maps of the three plasmids. The plasmids a and Ri have an apparently identical region and a partly homologous region, and are different in the remaining regions including their origins of replication. Another agropine-type A. rhizogenes strain, HRI, bears only one plasmid, which is the Ri plasmid (pRiHRI). pRiHRI and pRiA4 present the same restriction maps for a great part, but are different in a region of 48 kb; however, this region of pRiHRI is found unmodified in pArA4a and may have a role in the virulence of the bacteria. The comparison between the restriction maps of the plasmids of strain A4 leads us to propose that the recombination event leading to pArA4c formation occurs within the identical regions of pArA4a and pRiA4. In addition, the comparison with the already established map of pRiHRI suggests that strain HRI could have been derived from a recombination event between the two homologous regions of pArA4c with subsequent loss of the smaller plasmid.

Chromosome Mapping↗
PubMed1985

Isolation and identification of TL-DNA/plant junctions in Convolvulus arvensis transformed by Agrobacterium rhizogenes strain A4.

We have constructed a Charon 4A phage library containing insert DNA isolated from a morning glory (Convolvulus arvensis) plant (clone 7) regenerated from a root organ culture incited by Agrobacterium rhizogenes, strain A4. Using a subcloned region of the Ri plasmid as P-labeled probe, two lambda clones containing most of the 'left' T-DNA (TL) region were isolated. One of these lambda clones contains the left TL-DNA/plant junction, which was located by comparing nucleotide sequences from the appropriate regions of the Ri plasmid and this lambda clone. A 25-bp sequence found near this left TL-DNA/plant junction matches the 25-bp terminal sequence found at or near T-DNA/plant junctions of both nopaline- and octopine-type A. tumefaciens Ti plasmids. A possible location for the right Ri TL-DNA/plant junction in C. arvensis clone 7 was found by obtaining the nucleotide sequence surrounding its mapped location. Hybridization of plant DNA found adjacent to the left TL-DNA/plant junction against total C. arvensis DNA shows that this T-DNA integration occurred in a plant DNA region that does not contain highly repetitive DNA sequences. Nucleotide sequence analysis of 1004 bp of this plant DNA revealed no complete or partial open reading frames, but this plant DNA does have the potential to form various secondary structures which might play a role in the T-DNA integration event.

Journal Article↗
PubMed1984

Restriction map of an agropine-type Ri plasmid and its homologies with Ti plasmids.

The Ri plasmid of an agropine-type Agrobacterium rhizogenes, strain HRI, was cloned in a cosmid and mapped with the restriction endonucleases BamHI, EcoRI, KpnI, SmaI, and XbaI. This plasmid is almost identical to pRi1855 and pRiA4b. A study by Southern hybridizations of the homologies with octopine pTiB6806 and nopaline pTiC58 makes it possible to propose the localization of certain functions on this plasmid, such as virulence, agropine catabolism, agropine synthesis, and the origin of replication.

Base Sequence↗
PubMed1981

DNA sequence homology in Rhizobium meliloti plasmids.

Plasmids were recovered by an alkaline procedure from six symbiotically effective strains of Rhizobium meliloti of diverse geographical origin, reported to harbour only one middle-size large plasmid (ranging from 89 to 143 Megadaltons). Each purified plasmid was digested with eight restriction endonucleases; cleavage patterns were very complex: only KpnI and XbaI gave a limited number of bands. Fingerprints were very different, whatever the restriction enzyme or the geographical origin of the strains. However, Southern DNA-DNA hybridizations revealed that the plasmids showed homologous sequences having a high thermal stability. We gave evidence that some of these sequences are common to all the plasmids of R. meliloti. The biological function of these common sequences is unknown. Hybridization with cloned nitrogen fixation (nif) genes from Klebsiella pneumoniae had demonstrated that nif genes were not located on the middle -- size plasmids of R. meliloti studied in this paper.

Base Sequence↗
PubMed1978

Characterization of inverted repeated sequences in wheat nuclear DNA.

The properties of inverted repeated sequences in wheat nuclear DNA have been studied by HAP(1) chromatography, nuclease S1 digestion and electron microscopy. Inverted repeated sequences comprise 1.7% of wheat genome. The HAP studies show that the amount of "foldback HAP bound DNA" depends on DNA length. Inverted repeats appear to be clustered with an average intercluster distance of 25 kb. It is estimated that there are approximately 3 x 10(6) inverted repeats per haploid wheat genome. The sequences around inverted repeats involve all families of repetition frequencies. Inverted repeats are observed as hairpins in electron microscopy. 20% of hairpins are terminated by a single-stranded spacer ranging from 0.3 to 1.5 kb in length. Duplex regions of the inverted repeats range from 0.1 to 0.45 kb with number average values of 0.24 kb and 0.18 kb for unlooped and looped hairpin respectively. Thermal denaturations and nuclease S1 digestions have revealed a length of about 100 bases for duplex regions. The methods used to study inverted repeated sequences are compared and discussed.

Base Sequence↗
PubMedDate not supplied

The TR-DNA region carrying the auxin synthesis genes of the Agrobacterium rhizogenes agropine-type plasmid pRiA4: nucleotide sequence analysis and introduction into tobacco plants.

We have determined the nucleotide sequence of a 6-kilobase fragment of the Agrobacterium rhizogenes plasmid pRiA4 TR-region that carries genes (aux1 and aux2) responsible for auxin biosynthesis in transformed plant cells. Sequence analysis revealed two open reading frames corresponding to proteins of 749 amino acids for the aux1 gene and 466 amino acids for the aux2 gene. We observed significant similarity between the amino acid sequences deduced from the pRiA4 aux genes and those of the auxin biosynthesis genes of A. tumefaciens octopine-type Ti plasmids, the iaaM and iaaH genes of Pseudomonas savastanoi, and different genes of the pRiA4 TL-region; however, the 5'-flanking regions of the pRi and pTi auxin biosynthesis genes were found to be completely different. Transgenic tobacco plants containing this entire 6-kilobase fragment of the pRiA4 TR-region have been obtained. Regenerated plants are phenotypically normal. The aux1 gene is not or is very weakly expressed in these plants, but expression of the aux2 gene leads to a modified root phenotype when plants are grown on medium containing an auxin precursor (naphthalene acetamide).

Agrobacterium tumefaciens↗