Nuclear involvement of the Cell Division Cycle 48 protein during the plant immune response

The control of protein homeostasis, a balance between their synthesis and degradation, also called proteostasis, is essential for cell survival. Any imbalance of the proteome, for instance triggered by a stress, leads to an accumulation of misfolded proteins leading to proteotoxic stress that can induce cell death. The ubiquitin proteasome system (UPS) is a major actor in the selective degradation of misfolded proteins to preserve proteome balance.The chaperone-like Cdc48 is a member of the AAA+ ATPase enzyme family which isconserved in mammals (VCP), yeasts and plants (Cdc48: Cell Division Cycle 48/p97).Cdc48/VCP is a cytosolic and nuclear protein which segregates misfolded proteins fromsubcellular structures or protein complexes, and brings them to the proteasome to facilitate their recycling or degradation. Therefore, Cdc48/VCP is involved in numerous cellular pathways such as membranes associated degradation, cell cycle regulation, genome stability, vesicular trafficking, autophagy and apoptosis. The role of Cdc48 in response to biotic stresses has been investigated. However, nuclear function(s) of Cdc48 in plant immunity remain unclear and poorly understood.In this project, we aimed to characterize the nuclear function(s) of the Cdc48 protein during the plant immune response triggered by cryptogein (an elicitor produced by Phytophthora cryptogea) in tobacco cells. We analyzed the nuclear dynamic of Cdc48 under normal and elicitation conditions through Fluorescence Correlation Spectroscopy analysis (FCS). Thiscomparison has shown that during plant immune response, (i) the nuclear mobility of Cdc48 increased and (ii) Cdc48 interacted more quickly with more proteins. Then, nuclear partners interacting with the endogenous nuclear Cdc48 were identified through immunoprecipitation and mass spectrometry analysis.To summarize, this work provides new information regarding the role of Cdc48 and its dynamic in the nucleus during plant immunity.