RABC1-ABI1 module coordinates lipid droplet mobilization and post-germination growth arrest in Arabidopsis

Abscisic acid (ABA) promotes post-germination growth arrest (PGGA), thereby enhancing plant survival under adverse conditions such as high salinity. Lipid droplets (LDs) are universally conserved dynamic organelles that can store and mobilize neutral lipids for their multiple cellular roles. The molecular mechanism whereby a plant coordinates LD mobilization and PGGA in response to environmental stresses remains poorly understood. Here, we report that RABC1 deficiency enhances PGGA, which could be efficiently mitigated by either inhibiting ABA biosynthesis or promoting LD breakdown. ABI1 interacts with and dephosphorylates RABC1 and promotes the interactions between RABC1 and its effectors SEIPIN2 and SEIPIN3, consequently enhancing LD mobilization. Taken together, these results report a regulatory mechanism of LD mobilization for plant stress tolerance and highlight a concerted interplay between lipid metabolism and hormonal signaling.