Type-2 histones deacetylases and cryptogein-induced cell death in tabacco ; Les histones déacétylases de type 2 dans le contrôle de la mort cellulaire induite par la cryptogéine, un éliciteur des réactions de défense chez le tabac

Cryptogein, which is secreted by the oomycete Phytophthora cryptogea, is a proteinaceous elicitor of plant defense reactions that activates a set of signaling events leading to the hypersensitive response and to systemic acquired resistance. Although the early cytosolic signaling events induced by cryptogein are well described, the only nuclear events characterized to date are the variations in free calcium concentrations and defense-related gene expression. The characterization of the activation of cytosolic protein kinases, including WIPK and SIPK, by phosphorylation in response to cryptogein highlights the key-role played by posttranslational modifications in cryptogein-induced signaling events in tobacco cells. In this context, purification/sequencing approaches revealed that two redundant isoforms of type-2 nuclear histone deacetylases, NtHD2a and NtHD2b, were rapidly phosphorylated in cryptogein-treated tobacco cells.This thesis work is part of a comprehensive study of the role of NtHD2a/b in the establishment of the cell death process in tobacco cells and of the hypersensitive response in planta, in response to cryptogein. By using a pharmacological approach and overexpression and RNA interference-based approaches, we confirmed the involvement of NtHD2a/b as negative regulators of elicitin-induced cell death and we achieved a better understanding of cell death signaling events. The molecular events that underly the cell death process appear particularly complex and seem to involve the modulation of defense-related gene expression, de novo protein synthesis and protein kinase activation such as WIPK and SIPK.The study of (de)/acetylation events in tobacco cells treated by cryptogein and invalidated in NtHD2a/b expression suggests a role for posttranslational modifications in cryptogein-induced cell death. ; La cryptogéine, sécrétée par l’oomycète Phytophthora cryptogea, est un éliciteur protéique des réactions de défense qui active chez le tabac un ensemble d’événements de signalisation conduisant à la ...