Search PubMed⌕ Search

Biomedical subjects

A Marais

Publications and source records attributed to A Marais.

27 records · Page 2Linked to original sources
PubMed1996

Characterization of the recA gene regions of Spiroplasma citri and Spiroplasma melliferum.

In previous studies (A. Marais, J. M. Bove, and J. Renaudin, J. Bacteriol. 178:862-870, 1996), we have shown that the recA gene of Spiroplasma citri R8A2 was restricted to the first 390 nucleotides of the N-terminal part. PCR amplification and sequencing studies of five additional strains of S. citri have revealed that these strains had the same organization at the recA region as the R8A2 strain. In contrast to S. citri, Spiroplasma melliferum was found to contain a full-length recA gene. However, in all five S. melliferum strains tested, a TAA stop codon was found within the N-terminal region of the recA reading frame. Our results suggest that S. melliferum, as well as S. citri, is RecA deficient. In agreement with the recA mutant genotype of S. citri and S. melliferum, we have shown that these organisms are highly sensitive to UV irradiation.

Amino Acid Sequence↗
PubMed1996

Spiroplasma citri virus SpV1-derived cloning vector: deletion formation by illegitimate and homologous recombination in a spiroplasmal host strain which probably lacks a functional recA gene.

We have previously described the use of the replicative form (RF) of Spiroplasma citri virus SpV1 as a vector for expressing an epitope of the P1 adhesin protein from Mycoplasma pneumoniae in S. citri (A. Marais, J. M. Bové, S.F. Dallo, J. B. Baseman, and J. Renaudin, J. Bacteriol. 175:2783-2787, 1993). We have now studied the structural instability of the recombinant RF leading to loss of the DNA insert. Analyses of viral clones with deletions have shown that both illegitimate and homologous recombination were involved in deletion formation. For one such clone, deletion has occurred via a double crossing-over exchange between the circular free viral RF and SpV1 viral sequences present in the S. citri host chromosome. The homologous recombination process usually requires the RecA protein. However, characterization of the recA gene of the S. citri R8A2 host strain revealed that over two-thirds of the open reading frame of the recA gene was deleted from the C-terminal part, indicating that this particular strain is probably RecA deficient.

Amino Acid Sequence↗
PubMed1995

Integrative and free Spiroplasma citri oriC plasmids: expression of the Spiroplasma phoeniceum spiralin in Spiroplasma citri.

The replication region (oriC) of the Spiroplasma citri chromosome has been recently sequenced, and a 2-kbp DNA fragment was characterized as an autonomously replicating sequence (F. Ye, J. Renaudin, J. M. Bové, and F. Laigret, Curr. Microbiol. 29:23-29, 1994). In the present studies, we have combined this DNA fragment, containing the dnaA gene and the flanking dnaA boxes, with a ColE1-derived Escherichia coli replicon and the Tet M determinant, which confers resistance to tetracycline. The recombinant plasmid, named pBOT1, was introduced into S. citri cells, in which it replicated. Plasmid pBOT1 was shuttled from E. coli to S. citri and back to E. coli. In S. citri, replication of pBOT1 did not require the presence of a functional dnaA gene on the plasmid. However, the dnaA box region downstream of the dnaA gene was essential. Upon passaging of the S. citri transformants, the plasmid integrated into the spiroplasmal host chromosome by recombination at the replication origin. The integration process led to duplication of the oriC sequences. In contrast to the integrative pBOT1, plasmid pOT1, which does not contain the E. coli replicon, was stably maintained as a free extrachromosomal element. Plasmid pOT1 was used as a vector to introduce into S. citri the G fragment of the cytadhesin P1 gene of Mycoplasma pneumoniae and the spiralin gene of Spiroplasma phoeniceum. The recombinant plasmids, pOTPG with the G fragment and pOTPS with the spiralin gene, were stably maintained in spiroplasmal transformants. Expression of the heterologous S. phoeniceum spiralin in S. citri was demonstrated by Western immunoblotting.

Adhesins, Bacterial↗
PubMed1993

Expression in Spiroplasma citri of an epitope carried on the G fragment of the cytadhesin P1 gene from Mycoplasma pneumoniae.

We have previously described the use of the replicative form (RF) of Spiroplasma citri virus SpV1 as a vector for cloning and expressing foreign genes in S. citri, an organism which reads UGA as a tryptophan codon (C. Stamburski, J. Renaudin, and J.M. Bové, J. Bacteriol. 173:2225-2230, 1991). We now report cloning and expression in S. citri of the G fragment of cytadhesin P1 gene from Mycoplasma pneumoniae. The G fragment was inserted in the SpV1 RF downstream of a synthetic ribosome binding site and introduced into S. citri by electroporation. Northern (RNA) blot analyses showed that in S. citri, the G fragment was transcribed from an SpV1 RF promoter as a 1.2-kb mRNA. The translation product was detected by Western blotting (immunoblotting) with a rabbit antiserum raised against total proteins from M. pneumoniae (strain FH) and was proved to be P1 specific by using monoclonal antibodies specific for the G region of the P1 protein. The apparent molecular mass of the polypeptide (24.5 kDa) indicates that in S. citri, the G fragment was fully translated in spite of the seven UGA codons present in the reading frame.

Adhesins, Bacterial↗
PubMed1988

Role of polyamines and intracellular pH change in the hypertrophy of the denervated rat hemidiaphragm.

The transient hypertrophy of the denervated rat hemidiaphragm is associated with a rise in concentrations of putrescine and spermidine. Hypertrophy still occurs following denervation in rats injected with difluoromethylornithine which reduces the increase in spermidine and particularly putrescine levels. Administration of isobutylmethylxanthine tended to raise putrescine concentrations in the denervated but not innervated tissue. No evidence could be found that the enhanced protein synthesis rate in the denervated tissue is associated with an increase in intracellular pH.

1-Methyl-3-isobutylxanthine↗
PubMed1988

The effect of benzoic acid derivatives on Nicotiana tabacum growth in relation to PR-b1 production.

Using HPLC quantification, we have shown that benzoic acid derivatives stimulate PR-b1 protein synthesis in the leaf discs of Nicotiana tabacum Xanthi nc. The stimulation of PR-b protein synthesis during treatment with several benzoic acid derivatives is described for the first time in the root system of in vitro grown Nicotiana tabacum plantlets. In healthy in vitro grown plantlets the PR-b1 concentration is similar in roots and leaves (200 ng per gram of fresh material). During chemical treatment, however, the PR-b1 concentration increases to a lesser extent in roots than in leaves (10-fold higher in treated roots and 100-fold higher in treated leaves). Benzoic acid derivatives also have a detrimental effect on the growth of in vitro plantlets, which may be related to the accumulation of PR-b proteins.

Benzoates↗
PubMed1988

Luteolysis in early diestrous beagle bitches.

To induce luteolysis early in diestrus, 15 mated beagles were treated with 250 microg/kg prostaglandin F2alpha (PG), administered subcutaneously twice daily for 4 d, from Day 5 to Day 8 after the onset of cytological diestrus. They were divided into three groups of five bitches each: Group 1 received PG only. Group 2 received PG and 20 microg/kg/day bromocryptine orally. Group 3 received PG and 0.1 mg/kg/day dexamethasone intramuscularly. Fifteen untreated beagles served as controls. In each of the three treatment groups, four of the five bitches (80%) underwent complete luteolysis and did not whelp. The three bitches which did not undergo luteolysis whelped normally. All control bitches whelped normally. It was concluded that luteolysis is possible in bitches early in diestrus and the inclusion of bromocryptine or dexamethasone did not appear to influence luteolysis.

Journal Article↗
PubMedDate not supplied

Characterization of a gene cluster of Phytophthora cryptogea which codes for elicitins, proteins inducing a hypersensitive-like response in tobacco.

Elicitins, proteinaceous elicitors secreted by Phytophthora spp., act as inducers of a hypersensitive-like response in tobacco during incompatible interactions. We have isolated and cloned sequences encoding cryptogein and related isoforms from P. cryptogea that belong to the elicitin family. The isolation of a genomic clone led to the characterization of four clustered genes. Two of these genes encode distinct elicitins, and two genes would encode, if expressed, a class of highly acidic elicitins which had not been observed so far. Northern blots indicate that elicitin genes are expressed in the fungus grown in vitro, though at different levels. Southern hybridization revealed that elicitins are encoded by a multigene family in several other species of Phytophthora. Moreover, isolates of Phytophthora parasitica var. nicotianae, pathogenic to tobacco, which do not produce elicitins, possess several elicitin-encoding genes. Involvement of elicitins in plant-pathogen interactions is discussed.

Algal Proteins↗