The Arabidopsis NPK1-related protein kinases regulate responses triggered by the endoplasmic reticulum stress

The Arabidopsis NPK1-related Protein kinases ANP1-3 belong to the MAPKKK superfamily and were previously described to be crucial for cytokinesis, elicitor-induced immunity, and development. Lack of ANPs also induce a typical cell wall damage syndrome similar to that observed in plants treated with the endoplasmic reticulum (ER) stress inducer tunicamycin (Tm). Here, we investigated the possible involvement of ANPs in signaling events mediating the ER stress, characterized by the accumulation of unfolded/misfolded proteins in the ER and the activation of the unfolded protein response (UPR). We uncover a role of ANPs in the regulation of UPR activation and show that plants overexpressing ANPs display higher resistance to prolonged ER stress. The aim of this study is to generate knowledge on signaling mechanisms mediating the ER stress response and cell wall deposition and how they contribute to sense and adapt to adverse environmental clues.