GBPL3 is a novel plant nucleoporin that recruits RNA processing and transcription machinery at the nuclear basket by promoting condensates formation

Abstract

The basket of nuclear pore complex (NPC) is an assembly of flexible protein filaments and acts as a dynamic scaffold at the nucleoplasmic side that regulates various essential cellular processes, including nuclear transport, RNA processing, chromatin organization, and gene expression. However, the mechanisms behind the regulation are still poorly understood, especially in plants. Here, we identified a guanylate-binding protein (GBP)-like GTPase (GBPL3) as a specific component of the NPC basket in Arabidopsis. GBPL3 is located at the nuclear rim and confers robust physical and genetic interactions with various NPC and nucleoskeleton constituents. Proximity labeling proteomics experiment suggests that GBPL3 is predominantly distributed at the NPC basket and that it is intimately associated with chromatin remodelers, transcription regulators, and RNA processing machinery. Importantly, we found that GBPL3 promotes the formation of biomolecular condensates at the NPC basket, which is capable of recruiting its interactors. Loss of GBPL3 led to severely stunted plant growth, aberrant transcription of abiotic and biotic stress-related genes, and retention of total mRNA in the nucleus. These results suggest that GBPL3 is a plant-specific NPC basket component and can recruit transcription and RNA processing machinery through condensate formation to modulate gene expression and subsequent RNA processing, which is required for plant growth and stress responses.