The barley disease resistance protein AvrPphB Response 1 exhibits nucleocytoplasmic localization

Authors: Helm, Matthew; MYERS, ARIANA - US Department Of Agriculture (USDA); HILES, RACHEL - Purdue University; Jaiswal, Namrata; IYER-PASCUZZI, ANJALI - Purdue University; Scofield, Steven

Submitted to: microPublication Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/11/2026
Publication Date: 5/19/2026
Citation: Helm, M.D., Myers, A., Kelly, R., Jaiswal, N., Iyer-Pascuzzi, A., Scofield, S.R. 2026. The barley disease resistance protein AvrPphB Response 1 exhibits nucleocytoplasmic localization. microPublication Biology. https://doi.org/10.17912/micropub.biology.002041.
DOI: https://doi.org/10.17912/micropub.biology.002041

Interpretive Summary: Plants have their own immune system that helps them defend against diseases. Inside plant cells are special “alarm” proteins that can sense when harmful microbes are attacking. One of these alarm proteins from the crop plant barley is called PBR1. Scientists already knew that PBR1 can detect a bacterial attack, but they did not know where this protein is located inside the cell or whether its position changes when the protein is altered or turned off. In this study, we used highly advanced microscopes to track where PBR1 and different versions of it go inside plant cells. We found that PBR1 always stays in the main interior of the cell, no matter which parts of the protein are present or whether it is active. This information helps scientists better understand how plant immune systems work and supports future efforts to protect crops from disease.

Technical Abstract: Plant immunity is, in part, governed by intracellular immune receptor proteins known as nucleotide-binding leucine-rich repeat (NLR) proteins that detect the activity of pathogen-secreted effector proteins, and NLR function is often closely linked to their subcellular localization. We previously showed the barley NLR immune receptor AvrPphB Response 1 (PBR1) mediates recognition of the Pseudomonas syringae effector protease AvrPphB. However, the subcellular localization of PBR1 within plant cells as well as whether its localization is dictated by specific protein domains, activate state, or fluorescent tag placement has not been previously reported. To address this knowledge gap, we systemically examined the subcellular localization of full-length PBR1, its individual domains and truncations, an N-terminally tagged PBR1 derivative, and a signaling-inactive mutant using laser scanning confocal microscopy following Agrobacterium-mediated transient expression in Nicotiana benthamiana. Here, we show that PBR1 predominantly localizes to the nucleocytosol, and that all individual domains (CC, NB-ARC, and LRR), domains truncations (CC–NB-ARC and NB-ARC–LRR), the N-terminally tagged PBR1, and the inactive PBR1K203N derivative similarly localize to the nucleocytosol, despite none of the domains or truncations inducing immune signaling. Collectively, these data demonstrate that nucleocytosolic localization of PBR1 is independent of individual domains, activation state, or N-terminal tag placement, providing insights for future studies aimed at defining the requirements for PBR1-mediated immune signaling.