A phosphorylation-driven ubiquitination switch fine-tunes Alfin-like 7–induced ROS signaling in plant immunity

Abstract

Maintaining reactive oxygen species (ROS) homeostasis is essential for balancing growth-defense trade-offs in plants. Although the transcription factors (TFs) that regulate ROS production and scavenging genes have been studied, the regulation of these TFs to control ROS accumulation remains poorly understood. Here, we demonstrate that during N nucleotide-binding leucine-rich repeat–mediated immunity, Alfin-like 7 (AL7) is ubiquitinated by the ubiquitin protein ligase E3 component N-recognin 7 (UBR7). UBR7 interacts with AL7 and acts as a molecular brake to mediate the ubiquitination of AL7 at lysine-20, leading to its subsequent proteasomal degradation. UBR7 functions upstream of AL7 to reduce AL7-induced ROS accumulation during N-mediated defense. The phosphorylation of AL7 at serine-174 enhances its interaction with UBR7, thereby increasing AL7 ubiquitination and reducing AL7 stability. Our findings reveal a mechanism by which ROS accumulation is regulated through the phosphorylation and ubiquitination of a TF during the immune response. This ensures precise switching of ROS signaling to prevent excessive defense responses.