Novel coiled-coil proteins regulate exocyst association with cortical microtubules in xylem cells via the conserved oligomeric golgi-complex 2 protein.

Xylem vessel cells develop secondary cell walls in distinct patterns. Cortical microtubules are rearranged into distinct patterns and regulate secondary cell wall deposition; however, it is unclear how exocytotic membrane trafficking is linked to cortical microtubules. Here, we show that the novel coiled-coil proteins vesicle tethering 1 (VETH1) and VETH2 recruit EXO70A1, an exocyst subunit essential for correct patterning of secondary cell wall deposition, to cortical microtubules via the conserved oligomeric Golgi complex (COG) 2 protein. VETH1 and VETH2 encode an uncharacterized domain of an unknown function designated DUF869, and were preferentially up-regulated in xylem cells. VETH1-green fluorescent protein (GFP) and VETH2-GFP co-localized at novel vesicle-like small compartments, which exhibited microtubule plus-end-directed and end-tracking dynamics. VETH1 and VETH2 interacted with COG2, and this interaction promoted the association between cortical microtubules and EXO70A1 These results suggest that the VETH-COG2 complex ensures the correct secondary cell wall deposition pattern by recruiting exocyst components to cortical microtubules.