P-114 - Cleavage, Translocation, and Inhibition: The Dual Regulation of Membrane-Associated NACs in plant-microbe interactions

Land plants encode over 300 variants of membrane-associated transcription factors, emphasizing their role in environmental sensing. Tethered to membranes, these proteins activate and cleave in response to environmental cues, enabling nuclear translocation and gene regulation.
Here we investigate activation and translocation mechanisms of membrane-associated NAC transcription factors. We focus on the Arabidopsis ANAC013 cluster within the membrane-associated NACs, key regulators of cellular reactive oxygen species levels and organelle signaling. These proteins remain inactive while tethered to the ER via a C-terminal transmembrane domain. Rhomboid-like proteases mediate their cleavage, releasing the transcription factor domain. Our data indicate that translocation depends on phosphorylation and 14-3-3 protein interaction. Furthermore, RXLR effectors co-localize and interact with ANAC013/017 proteins in planta. Results indicate these effectors inhibit translocation by interacting with the critical Rhomboid recognition domain, preventing cleavage. Interestingly, analysis of the effectors revealed a distinct conserved motif in the transmembrane domain, potentially involved in both NAC-effector and effector-effector interactions. ANAC013/017 are key regulators of retrograde signaling and ROS regulation, functioning as central hubs in signaling crosstalk. We will discuss our findings in the context of existing knowledge to highlight their broader role in plant stress responses.