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Éric Dion

Université Laval

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Sylvain Moineau

Université Laval

François Belzile

Centre Hospitalier Universitaire de Sherbrooke

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Éric Émond

Université Laval

Martine Jean

Université Laval

Richard Gabriel

Protagen (Germany)

Jeffery K. Kondo

Université Laval

E. R. Vedamuthu

Corvallis Environmental Center

Shirley A. Walker

University of Mary Hardin–Baylor

Frédéric Bissonnette

Groupe de Recherche en Économie Théorique et Appliquée

Diane Montpetit

Agriculture and Agri-Food Canada

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Université Laval

Université de Sherbrooke

Centre Hospitalier Universitaire de Sherbrooke

Groupe de Recherche en Économie Théorique et Appliquée

Oregon State University

North Carolina State University

Ministry of Agriculture, Fisheries and Food

Université de Montréal

McGill University

Guizhou University

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The Arabidopsis DNA mismatch repair gene PMS1 restricts somatic recombination between homeologous sequences

Plant Molecular Biology (2008)

Liangliang Li Éric Dion Richard Gabriel Olivier Domingue Martine Jean

Gene conversion

Non-allelic homologous recombination

Ectopic recombination

10.1007/s11103-008-9447-9

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Citations (23)

Microbiological and molecular impacts of AbiK on the lytic cycle of Lactococcus lactis phages of the 936 and P335 species

Microbiology (2000)

Isabelle Boucher Éric Émond Éric Dion Diane Montpetit Sylvain Moineau

The lactococcal abortive infection mechanism AbiK was previously shown to be highly effective against the small isometric-headed bacteriophage ul36 of the P335 species, as evidenced by an efficiency of plaquing (e.o.p.) of 10−6, a 14-fold reduction in the burst size and an efficiency at which centres of infection form (e.c.o.i.) of 0·5%. No phage DNA was detected in the infected AbiK+ cells [Émond, É., Holler, B. J., Boucher, I., Vandenbergh, P. A., Vedamuthu, E. R., Kondo, J. K. & Moineau, S. (1997) R15 . Appl Environ Microbiol 63, 1274–1283]. Here, the effects of AbiK are compared on the small isometric-headed phages p2 and P008 (936 species) and on the phage P335 (P335 species). The microbiological impacts of AbiK on p2 were relatively similar to those reported for ul36, with an e.o.p. of 10−6, an 11-fold reduction in the burst size and an e.c.o.i. of 5%. Contrary to phage ul36, replication of phage p2 DNA was observed in the AbiK+ cells. Only immature forms (concatemeric and circular DNA) of phage p2 DNA were found, indicating that the presence of AbiK prevented phage DNA maturation. These distinct molecular consequences of AbiK were also observed for phages P335 and P008, two phages that propagate on the same host. To the knowledge of the authors, this is the first time that different phage responses towards an Abi system have been reported.

Lytic cycle

10.1099/00221287-146-2-445

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Citations (41)

AbiQ, an Abortive Infection Mechanism fromLactococcus lactis

Applied and Environmental Microbiology (1998)

Éric Émond Éric Dion Shirley A. Walker E. R. Vedamuthu Jeffery K. Kondo

ABSTRACT Lactococcus lactis W-37 is highly resistant to phage infection. The cryptic plasmids from this strain were coelectroporated, along with the shuttle vector pSA3, into the plasmid-free host L. lactis LM0230. In addition to pSA3, erythromycin- and phage-resistant isolates carried pSRQ900, an 11-kb plasmid from L. lactis W-37. This plasmid made the host bacteria highly resistant (efficiency of plaquing <10 −8 ) to c2- and 936-like phages. pSRQ900 did not confer any resistance to phages of the P335 species. Adsorption, cell survival, and endonucleolytic activity assays showed that pSRQ900 encodes an abortive infection mechanism. The phage resistance mechanism is limited to a 2.2-kb Eco RV/ Bcl I fragment. Sequence analysis of this fragment revealed a complete open reading frame ( abiQ ), which encodes a putative protein of 183 amino acids. A frameshift mutation within abiQ completely abolished the resistant phenotype. The predicted peptide has a high content of positively charged residues (pI = 10.5) and is, in all likelihood, a cytosolic protein. AbiQ has no homology to known or deduced proteins in the databases. DNA replication assays showed that phage c21 (c2-like) and phage p2 (936-like) can still replicate in cells harboring AbiQ. However, phage DNA accumulated in its concatenated form in the infected AbiQ + cells, whereas the AbiQ − cells contained processed (mature) phage DNA in addition to the concatenated form. The production of the major capsid protein of phage c21 was not hindered in the cells harboring AbiQ.

Shuttle vector

Phagemid

10.1128/aem.64.12.4748-4756.1998

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Citations (79)

An Arabidopsis MLH1 mutant exhibits reproductive defects and reveals a dual role for this gene in mitotic recombination

The Plant Journal (2007)

Éric Dion Liangliang Li Martine Jean François Belzile

Summary The eukaryotic DNA mismatch repair (MMR) system contributes to maintaining genome integrity and DNA sequence fidelity in at least two important ways: by correcting errors arising during DNA replication, and also by preventing recombination events between divergent sequences. This study aimed to investigate the role of one key MMR gene in recombination. We obtained a mutant line in which the AtMLH1 gene has been disrupted by the insertion of a T‐DNA within the coding region. Transcript analysis indicated that no full‐length transcript was produced in mutant plants. The loss of a functional AtMLH1 gene led to a significant reduction in fertility in both homozygotes and heterozygotes, and we observed a strong bias against transmission of the mutant allele. To investigate the role of AtMLH1 in mitotic recombination, the mutant was crossed to a series of recombination reporter lines. A strong decrease (72%) in the frequency of homologous recombination was observed in the mutant. However, the decline in recombination due to homeology was less severe in the Atmlh1 mutant than in a wild‐type control. These data demonstrate a dual role for AtMLH1 in recombination: it is both required for recombination and acts to limit recombination between diverged sequences.

Mitotic crossover

Ectopic recombination

Non-allelic homologous recombination

FLP-FRT recombination

Gene conversion

Gene targeting

10.1111/j.1365-313x.2007.03145.x

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Citations (56)

Characterization of the Two-Component Abortive Phage Infection Mechanism AbiT from Lactococcus lactis

Journal of Bacteriology (2002)

Julie D. Bouchard Éric Dion Frédéric Bissonnette Sylvain Moineau

ABSTRACT During the production of fermented dairy products, virulent bacteriophages infecting Lactococcus lactis can delay or stop the milk acidification process. A solution to this biological problem consists of introducing natural phage barriers into the strains used by the dairy industry. One such hurdle is called abortive infection (Abi) and causes premature cell death with no or little phage progeny. Here, we describe the isolation and characterization of a novel Abi mechanism encoded by plasmid pED1 from L. lactis . The system is composed of two constitutively cotranscribed genes encoding putative proteins of 127 and 213 amino acids, named AbiTi and AbiTii, respectively. Site-directed mutagenesis indicated that a hydrophobic region at the C-terminal extremity of AbiTi is essential to the antiphage phenotype. The AbiT system is effective against phages of the 936 and P335 species (efficiency of plaquing between 10 −5 and 10 −7 ) and causes a 20-fold reduction in the efficiency to form centers of infection as well as a 10- to 12-fold reduction in the burst size. Its efficacy could be improved by raising the plasmid copy number, but changing the intrinsic ratio of AbiTi and AbiTii did not greatly affect the antiphage activity. The monitoring of the intracellular phage infection process by DNA replication, gene expression, and electron microscopy as well as the study of phage mutants by genome mapping indicated that AbiT is likely to act at a later stage of the phage lytic cycle.

Lytic cycle

Phagemid

Prophage

Lactococcus

10.1128/jb.184.22.6325-6332.2002

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Citations (65)