Identification of nuclear pore proteins at plasmodesmata

Plasmodesmata (PD) exchange small molecules, RNAs and proteins between plant cells with an exclusion limit for passive, non-specific transport. PD also facilitate the transport of specific cargo that may require chaperones or carriers for transport. The mechanisms underlying PD transport are not understood. PD and nuclear pore complexes (NPC), are nanometer size micropores with similar transport properties. The permeability barrier in NPCs is a phase separation domain formed by FG-nucleoporins (FG-NUP). Here we used bioinformatics, proteomics and fluorescence imaging to identify proteins with similarities to phase separating FG-NUPs at PD. We identified 20 NUPs in PD fractions, and validated dual localization to NPC and PD for 7 NUPs. Structured illumination microscopy detected the transmembrane anchor NUP CPR5 at both orifices of PD. cpr5 mutants showed reduced intercellular transport of SHR from stele to endodermis. The identification of FG-NUPs at PD is consistent with the recruitment of NUPs in the green lineage to form a PD pore gating complex consistent with liquid phase separation domains as diffusion barriers at PD.