GBPL3 localizes to the nuclear pore complex and functionally connects the nuclear basket with the nucleoskeleton in plants

Abstract

The nuclear basket (NB) is an essential structure of the nuclear pore complex (NPC) and serves as a dynamic and multifunctional platform that participates in various critical nuclear processes, including cargo transport, molecular docking, and gene expression regulation. However, the underlying molecular mechanisms are not completely understood, particularly in plants. Here, we identified a guanylate-binding protein (GBP)-like GTPase (GBPL3) as a novel NPC basket component in Arabidopsis. Using fluorescence and immunoelectron microscopy, we found that GBPL3 localizes to the nuclear rim and is enriched in the nuclear pore. Proximity labeling proteomics and protein-protein interaction assays revealed that GBPL3 is predominantly distributed at the NPC basket, where it physically associates with NB nucleoporins and recruits chromatin remodelers, transcription apparatus and regulators, and the RNA splicing and processing machinery, suggesting a conserved function of the NB in transcription regulation as reported in yeasts and animals. Moreover, we found that GBPL3 physically interacts with the nucleoskeleton via disordered coiled-coil regions. Simultaneous loss of GBPL3 and one of the 4 Arabidopsis nucleoskeleton genes CRWNs led to distinct development- and stress-related phenotypes, ranging from seedling lethality to lesion development, and aberrant transcription of stress-related genes. Our results indicate that GBPL3 is a bona fide component of the plant NPC and physically and functionally connects the NB with the nucleoskeleton, which is required for the coordination of gene expression during plant development and stress responses.