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Accueil du site > Equipes de recherche > Immunité Végétale et Effecteurs > Thèmes de recherche > Characterization of oomycete PAMPs, and perception mechanisms

Characterization of oomycete PAMPs, and perception mechanisms

Contact : mail to Bernard DUMAS, mail to Christophe JACQUET

The microbial cell wall is a structure playing a central role at the host-pathogen interface. Notably, its proteins and polysaccharides are reservoirs of PAMPs (Pathogen-Associated Molecular Patterns) involved in induction of plant immunity. Chitin is a structural crystalline polymer of the fungal cell wall, and fragments thereof (chitooligosaccharides) are widely studied PAMPs that are recognized by LysM-containing receptors in plants. In Legumes, this type of receptor is also involved in perception of Nod factors, lipochitooligosaccharides produced by nitrogen-fixing symbiotic bacteria such as Sinorhizobium. This raises the question of the mechanisms underlying the discrimination between structurally-related pathogenic and symbiotic signals by closely related receptors. Whereas phytopathogenic oomycetes such as Phytophthora have a cellulosic cell wall devoid of chitin, analysis of the cell wall of Aphanomyces euteiches showed the presence of chitosaccharides, compounds resembling chitin but of non-crystalline structure.
Ongoing work aims at characterizing these compounds (biosynthesis, purification and structural characterization), their biological activity (induction of defense-associated reactions), and the involvement of LysM receptors in their perception by the host legume plant Medicago truncatula (reverse genetics appproaches). The ongoing sequencing of the A. euteiches genome will allow the identification of new PAMPs as well as of enzymes involved in their biosynthesis, through bioinformatic analyses of the generated sequences but also proteomic analyses of the microbial cell wall and secretome.

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Perception of pathogenic and symbiotic signals in Medicago truncatula. Pathogenic and symbiotic microorganisms can produced signalling molecules sharing common characteristic but inducing contrasting responses in plants, either immunity (rejection) of symbiosis (acceptation). Moreover, perception of these molecules involved similar receptors (Receptor-Like Kinases containing extracellular LysM domains such as NFP and LyK3). These findings raise the question of how plants can distinguish friends and foes to respond with the right response to these signals.