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RESEARCH PRODUCT

Cryptogein signaling in tobacco: in search for nitric oxide targets

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Nitric oxide (NO) triggers various physiological responses in plants. Notably, NO is recognized to account for the response to biotic stresses. We previously reported that NO is produced in tobacco cells exposed to cryptogein, a 10 kDa elicitor secreted by the oomycete Phytophthora cryptogea. To decipher the role of NO, we identified and characterized S-nitrosylated proteins in tobacco cell suspensions elicited by cryptogein. Several candidates were identified including the chaperone-like AAA+ATPase CDC48 and a calmodulin isoform (CaM). Interestingly, the Cys residue undergoing S-nitrosylation in CaM is located in the first Ca2+ binding EF hand and is not or poorly conserved in other organisms. The possibility that NO regulates CaM at a post-translational level further confirms our previous finding that NO and Ca2+ works together in plant immune signalling. To complete our investigation, we undertook a microarray analysis in order to identify cryptogein-modulated genes regulated through a NO-dependent process. Part of the genes of interest were also reactive oxygen species (ROS)-dependent, highlighting the occurrence of a cross-talk between NO and ROS. The mechanisms underlying this cross-talk will be discussed.