DIRECT FUNCTIONAL ASSAY FOR TOBACCO MOSAIC-VIRUS CELL-TO-CELL MOVEMENT PROTEIN AND IDENTIFICATION OF A DOMAIN INVOLVED IN INCREASING PLASMODESMAL PERMEABILITY
E. Waigmann et al., DIRECT FUNCTIONAL ASSAY FOR TOBACCO MOSAIC-VIRUS CELL-TO-CELL MOVEMENT PROTEIN AND IDENTIFICATION OF A DOMAIN INVOLVED IN INCREASING PLASMODESMAL PERMEABILITY, Proceedings of the National Academy of Sciences of the United Statesof America, 91(4), 1994, pp. 1433-1437
Plasmodesmata are cytoplasmic bridges between plant cells thought to g
enerally allow only the passage of small molecules and metabolites. Ho
wever, large structures such as plant viruses also move from cell to c
ell via plasmodesmata. In tobacco mosaic virus (TMV) infection a viral
movement protein (TMV-MP) mediates viral spread. Here, a microinjecti
on assay is used to monitor the dynamics of TMV-MP function directly i
n wild-type plants. The results indicate that TMV-MP interacts with an
endogenous plant pathway increasing plasmodesmal size exclusion limit
to permit passage of 20-kDa dextrans. Furthermore, TMV-MP influences
plasmodesmal size exclusion limit several cells distant from the injec
tion site, indicating either that TMV-MP itself crosses plasmodesmata
or that TMV-MP induces a diffusable signal capable of dilating microch
annels of plasmodesmata. The region of TMV-MP responsible for increasi
ng plasmodesmal size exclusion limit was mapped to the carboxyl-termin
al part of the 268-amino acid residue protein between amino acid resid
ues 126 and 224.