Small GTPase RAN-driven PNET2 oligomerization and phase separation at the nuclear lamina promote nuclear envelope...

The nuclear envelope is a fundamental organizer of eukaryotic cells, yet how its architecture and integrity are regulated in plants remains poorly understood. Here we identify that plant inner nuclear membrane protein PNET2 as a central scaffold that maintains nuclear envelope integrity and genome stability. Loss of PNET2 compromises nuclear membrane structure and sensitizes cells to DNA damage, whereas overexpression drives aberrant expansion of the nuclear membrane. Mechanistically, PNET2 cooperates with the nuclear lamin protein KAKU4 and CRWN1 within the nuclear lamina to promote nuclear membrane remodeling, a process driven by biomolecular condensate formation via their intrinsically disordered regions. We further uncover a direct interaction between PNET2 and the small GTPase RAN. Structural modelling and biochemical analyses reveal its active GTP-bound form stimulates PNET2 oligomerization, potentially promoting its phase separation to drive membrane expansion. Genetic analyses confirm that PNET2 and RAN function in a shared pathway essential for nuclear membrane integrity. Together, our findings define a regulatory module that orchestrates GTPase signaling to control nuclear membrane homeostasis in plants, positioning PNET2 as a key nexus linking membrane dynamics, nuclear lamina organization, and genome protection.