Elucidation of the Arabidopsis NPK1-related Protein kinases (ANPs) role in danger signalling

Plants deploy an enormous number of cell-surface and intracellular immune receptors to perceive danger signals. Danger signal is transmitted inside the plant cells by activated key immune signaling modules and involves several subcellular organelles and interactions between them, coordinated by the exchange of metabolites and signaling molecules, including calcium and reactive oxygen species. Membrane dynamics, cytoskeletal rearrangements and protein transport are essential for the proper activation of plant immune mechanisms and, therefore, critical plant trafficking regulators represent favorite targets of pathogen effectors. Arabidopsis NPK1-related Protein kinases ANP1, ANP2 and ANP3 are MAP kinase kinase kinases that have been shown to be key regulators of essential physiological processes, such as cytokinesis, resistance to pathogens, ROS homeostasis. Moreover, multiple anp double KO and silenced triple mutants display reduced growth, spontaneous cell death and constitutive resistance to Botrytis as well as higher susceptibility to Pst DC3000 hrcC-. Most of the above listed processes are also regulated by JA, which in fact was found to be considerably higher in anp double and triple mutants, suggesting a possible role for ANPs as negative regulators of JA biosynthesis/accumulation. We show here that, lack of ANPs also prevents the expression of downstream jasmonate target genes VSP1 and VSP2, accompanied by an overexpression of ORA59, PDF1.2 and THI2.1, hinting a role of these MAP3Ks in regulating the MYC2-dependent branch in response to JA. Moreover, we show here a novel function of these kinases in the actin cytoskeleton organization and Golgi bodies motility. Elucidation of how danger signalling is generated at a cellular level and transmitted sub-cellularly and to the hole plant will allow the combination of basic research derived knowledge with fast and precise genetic engineering techniques