Delivery of endocytosed proteins to the cell-division plane requires change of pathway from recycling to secretion

Membrane trafficking is essential to fundamental processes in eukaryotic life, including cell growth and division. In plant cytokinesis, post-Golgi trafficking mediates a massive flow of vesicles that form the partitioning membrane but its regulation remains poorly understood. Here, we identify functionally redundant Arabidopsis ARF guanine-nucleotide exchange factors (ARF-GEFs) BIG1-BIG4 as regulators of post-Golgi trafficking, mediating late secretion from the trans-Golgi network but not recycling of endocytosed proteins to the plasma membrane, although the TGN also functions as an early endosome in plants. In contrast, BIG1-4 are absolutely required for trafficking of both endocytosed and newly synthesized proteins to the cell-division plane during cytokinesis, counteracting recycling to the plasma membrane. This change from recycling to secretory trafficking pathway mediated by ARF-GEFs confers specificity of cargo delivery to the division plane and might thus ensure that the partitioning membrane is completed on time in the absence of a cytokinesis-interphase checkpoint.