Background Plant viruses move through plasmodesmata (PD) to infect new cells. To overcome the PD barrier, plant viruses have developed specific protein(s) to guide their genomic RNAs or DNAs to path through the PD. Results In the present study, we analyzed the function of Pepper vein yellows virus P4 protein. Our bioinformatic analysis showed that the P4 protein contains an transmembrane domain, encompassing the amino acid residue 117-138. The P4 protein was found to target PD and form small

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... ctates near walls. The P4 deletion mutant or the substitution mutant lost their function to produce punctates near the walls inside the fluorescent loci. The P4-YFP fusion was found to move from cell to cell in infiltrated leaves, and P4 could complement Cucumber mosaic virus movement protein deficiency mutant to move between cells. Conclustion Taking together, we consider that the P4 protein is a movement protein of Pepper vein yellows virus.