Component of the exocyst complex involved in the docking of exocytic vesicles with fusion sites on the plasma membrane during regulated or polarized secretion (PubMed:31299202). Involved in PIN4 exocytosis and gravitropic responses in columella cells (PubMed:31299202). By monitoring PIN4 distribution in columella cells, modulates auxin repartition and subsequently regulates the root system architecture (RSA), thus being a component of the auxin-dependent root directional growth (ARD) (PubMed:31299202). Subunit of the exocyst complex. Confined to the outer layer of the columella cells in the root tips of young seedlings. Alteration of root gravitropic responses (e.g. delay, auxin-dependent root directional growth and larger variation of root tip angles) resulting in deeper root system architecture (RSA) and enhanced drought resistance (PubMed:31299202). Disturbed PIN4 distribution in columella cells associated with a perturbation of the auxin distribution pattern and an asymmetric accumulation of DR5 in the downward peripheral layer under gravistimulus (PubMed:31299202). Associated with natural variation of agravitropic root growth upon auxin transport perturbation with N-1-naphtylphthalamic acid (NPA). Belongs to the EXO70 family.