NO signaling in tobacco elicited by the MAMP cryptogein

Abstract

SPEPôle IPMInternational audienceDuring the past years, nitric oxide (NO) has been shown to be a major cell signaling messenger in plants. Its importance has been highlighted during plant responses to pathogen attack or MAMPs (microbe associated molecular patterns) and during induced resistance or priming phenomenon. The major focus of our research is to understand how nitric oxide can modulate the activity of protein involved in plant defense. We identified several proteins undergoing S-nitrosylation, a redox-based post-translational modification of proteins, in tobacco cells elicited by cryptogein, a 10 kDa protein produced by the oomycete Phytophthora cryptogea and inducing immune responses in tobacco. These proteins include the chaperone-like AAA+-ATPase CDC48 and a calmodulin isoform. The incidence of NO on the structure and function of both proteins has been investigated. Concerning CDC48, the S-nitrosylated cystein is located in the vicinity of the ATP binding site in the second ATPase domain. Its S-nitrosylation triggers local structural changes that correlates with a strong reduction of the ATPase activity. Calmodulins are Ca2+ sensors that decode Ca2+ signals in all eukaryotes organisms. Ca2+ binds to 4 EF-hand domains inducing a conformational change of the protein. This change is required for CaM binding to target protein then modulating their activities. We showed that a recombinant CaM is S-nitrosylated on a unique cystein residue either in the presence or in the absence of Ca2+. This cystein residue is located in the first EF-hand domain suggesting a role of the S-nitrosylation in CaM function. Through the identification of new components of NO signaling, our work further supports the concept that NO is a key mediator in the signaling cascade leading to immune responses in plants