In Arabidopsis, SYNTAXIN OF PLANTS 132 (SYP132) is an evolutionarily ancient SNARE that functions with syntaxins SYP121 and SYP122 at the plasma membrane. Whereas SYP121 and SYP122 mediate overlapping secretory pathways, albeit with differences in their importance in plant-environment interactions, the SNARE SYP132 is absolutely essential for plant development and survival. SYP132 promotes endocytic traffic of the plasma membrane H+-ATPase AHA1 and aquaporin PIP2;1, and it coordinates plant growth and bacterial pathogen immunity through PATHOGENESIS-RELATED1 (PR1) secretion. Yet, little else is known about SYP132 cargoes. Here, we used advanced quantitative Tandem Mass Tagging (TMT) mass spectrometry (MS) combined with immunoblot assays to track native secreted cargo proteins in the leaf apoplast from wild type, syp121/syp122 double mutant and Arabidopsis transgenics that exhibit altered SYP132 functions, SYP132-OX and SYP132Deterrent.