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Endomembrane protein (EMP) belongs to the evolutionarily conserved transmembrane nine superfamily, which is characterized by the presence of a large lumenal N-terminal region, followed by nine putative transmembrane domains (TMD) and a short cytoplasmic tail (CT).In Arabidopsis, there are 12 EMP isoforms (termed AtEMP1 to AtEMP12 in this study) with little information about their subcellular localization and function.Here we study the subcellular localization and trafficking of AtEMP12 in Arabidopsis and demonstrated that 1) both endogenous AtEMP12 (detected by AtEMP12 antibodies) and (GFP)-AtEMP12 fusion localized to the Golgi apparatus in Arabidopsis plants; 2) GFP fusion at the C-terminus of AtEMP12 caused mis-localization of AtEMP12-GFP to reach post-Golgi compartments and vacuoles for degradation in Arabidopsis cells; 3) mutagenesis and biochemical analysis showed that the AtEMP12 CT contains dual sorting signals: an ER export motif and a Golgi retention signal that interact with COPII and COPI subunit respectively; 4) gain-of-function analysis further demonstrated that the Golgi retention motif of AtEMP12 retained post-Golgi membrane proteins within the Golgi apparatus.These sorting signals are highly conserved in all the plant EMP isoforms, thus likely representing a general mechanism for EMP targeting in plant cells.Our research programs have been supported by grants from the Research Grants Council (RGC) of Hong Kong and CUHK Schemes.