Modulates cell-to-cell trafficking. (Microbial infection) Interacts with Grapevine fanleaf virus (GFLV) 2B-MP. Co-localizes with the Grapevine fanleaf virus (GFLV) 2B-MP at the base of tubules within modified plasmodesmata. Highly expressed in inflorescence shoot apex. Uniformly expressed within the inflorescence meristem with the exception of a boundary zone between floral primordia and the meristem where the expression is weaker (at protein level). Grows normally showing no detectable abnormalities in leaf or flower development under short or long day growth conditions. The pdlp2 and pdlp3 double mutant shows altered protein diffusion (measured using GFP). In pdlp1, pdlp2 and pdlp3 triple mutant there is inhibition of GFLV 2BMP tubule formation. Virus cell-to-cell movement is negatively affected. There is a 22% reduction in mean surface area of infection foci by GFLV and an approximately 12 h delay in long distance movement in comparison to wild-type plants. There is also a systemic delay in Cauliflower mosaic virus (CaMV) spread. Belongs to the cysteine-rich repeat secretory protein family. Plasmodesmata-located proteins (PDLD) subfamily. PDLPs were initially named Cysteine-rich secretory proteins based on a classification work that failed to predict the transmembrane region at the C-terminus (PubMed:11402176). However, it was later shown that PDLPs are membrane proteins.