Plant responses to salt stress include an altered root architecture mediated by ion imbalances, reactive oxygen species (ROS) accumulation, and altered hormonal responses. Auxin is implicated in these processes. To understand better the molecular network we investigated the role of VAMP714, an R-SNARE essential for correct trafficking of the auxin efflux carrier PIN-FORMED (PIN) proteins (implicated in the salt stress response), but also with a reported role in ROS vesicular transport in Arabidopsis. We show that under salt stress the VAMP714 gene shows a rapid transient increase in expression but subsequent perturbed localization of VAMP714 and PIN proteins and altered auxin-responsive gene expression. RNA-seq analysis revealed that pathways related to oxygen signaling, SALT OVERLY SENSITIVE (SOS) pathway activation and ROS response are influenced by salt stress in a VAMP714-dependent manner. Low levels of transgenic overexpression of VAMP714 enhanced root salt tolerance, an effect enhanced by exogenous auxin, showing that maintenance of VAMP714 expression under salt stress allows auxin-mediated maintenance of root growth. We conclude that VAMP714 contributes to the coordinated regulation of auxin signaling and the SOS pathway during salt stress via distinct roles in vesicle trafficking to the plasma membrane (for auxin) and vacuole (for SOS).
Sun et al. (Tue,) studied this question.