Plasmodesmata are the conduits for many non–cell-autonomous proteins (NCAPs). Lee et al. figured that some NCAPs might bind to plasmodesmal proteins, so they used an affinity column based on an NCAP called CmPP16 and a cell wall fraction highly enriched for plasmodesmal proteins to identify NCAPP1.
As expected for a plasmodesmal function, colocalization of NCAPP1 and CmPP16 was observed at the ER near the orifice to plasmodesmata. A dominant–negative form of NCAPP1 altered trafficking of the NCAPs CmPP16, LEAFY, and the movement protein of Tobacco mosaic virus, but left trafficking of other NCAPs unaffected. Thus, NCAP movement is a regulated process, similar to nuclear pore trafficking. Lucas' group is now purifying other potential plasmodesmal proteins that traffic NCAPP1-independent cargos. ▪