The physiological role of SYP4 in the salinity and osmotic stress tolerances

The trans-Golgi network (TGN) contains multiple sorting domains and acts as the compartment for cargo sorting. Recent evidence indicates that the TGN also functions as an early endosome, the first compartment in the endocytic pathway in plants. The SYP4 group, plant Qa-SNAREs localized on the TGN, regulates both secretory and vacuolar transport pathways. Consistent with a secretory role, SYP4 proteins are required for extracellular resistance to fungal pathogens. However, the physiological role of SYP4 in abiotic stress remains unknown. Here, we report the phenotypes of a syp4-mutant in regard to salinity and osmotic response, and describe the physiological roles of the SYP4 group in the abiotic stress response.