The Ral small GTPase is an essential regulator of exocyst complex function in secretion.

Abstract

Ral GTPases have long been proposed as regulators of the metazoan exocyst, a conserved secretory vesicle-tethering complex, but direct evidence for this role has been scarce. In contrast, the well-studied yeast exocyst relies on multiple Rab GTPases to regulate function, but yeast do not encode Ral. Using Caenorhabditis elegans, we demonstrate that endogenous RAL-1 directly engages the exocyst through conserved binding sites in its subunits. Loss of RAL-1 disrupts dendritic arborization of PVD sensory neurons, impairs vesicle trafficking, and causes broad developmental defects, acting both cell autonomously in neurons and non-autonomously through supporting epithelial cells. Structure-guided genome editing of RAL-1-exocyst interfaces produced synthetic phenotypes, underscoring the physiological importance of these contacts. Taken together, our findings establish RAL-1 as a bona fide regulator of the metazoan exocyst in vivo and suggest that Ral-exocyst interactions operate in parallel with other secretory pathways. More broadly, this work positions C. elegans as a powerful system to dissect Ral-exocyst mechanisms across molecular, cellular, and developmental scales.