Pleiotropic regulatory locus 1 maintains actin cytoskeleton integrity and cellular homeostasis to enable Arabidopsis root growth.

Cell functions are based on the integrity of actin filaments. The actin cytoskeleton is typically the target but also the source of signals. Arabidopsis PRL1 (Pleiotropic Regulatory Locus 1), regulates multiple cellular processes and physiological responses. However, the precise mechanisms underlying PRL1s multiple functions are unclear. Here, we show that PRL1 maintains actin integrity and concomitant cellular homeostasis. The cortical actin cytoskeleton was de-polymerized in the mutant, causing the developmental root defect. Actin depolymerization, rather than reactive oxygen species (ROS) imbalance, constituted the fundamental cause of retarded root growth in . upregulation by, and cooperation with, actin depolymerization triggered stele cell death in roots. Differential gene expression and alternative splicing defects resulting from actin depolymerization occurred independently in . Our work establishes the cause-effect relationships between actin depolymerization and downstream stress-related signals, revealing a novel function of PRL1 and enhancing the understanding of PRLs functional mechanisms.