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J. Bacteriol., May 1995, 2870-2877, Vol 177, No. 10
J Renaudin, A Marais, E Verdin, S Duret, X Foissac, F Laigret and JM Bove
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. Bove, 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.
Copyright © 1995, American Society for Microbiology
Integrative and free Spiroplasma citri oriC plasmids: expression of the Spiroplasma phoeniceum spiralin in Spiroplasma citri
Laboratoire de Biologie Cellulaire et Moleculaire, Institut National de la Recherche Agronomique, Villenave d'Ornon, France.
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