Vz. Li et al., CELL-TO-CELL MOVEMENT OF TURNIP CRINKLE VIRUS IS CONTROLLED BY 2 SMALL OPEN READING FRAMES THAT FUNCTION IN TRANS, Virology, 244(2), 1998, pp. 405-416
Previous studies on turnip crinkle virus (TCV) have suggested that the
two small, centrally located ORFs, conserved in all Carmoviruses, are
both required for cell-to-cell movement (Hacker et al., 1992). We now
demonstrate that the cell-to-cell movement of TCV is mediated by in t
rans complementation of the two proteins. First, both of the putative
movement proteins (MPs p8 and p9) were shown to be translated in vitro
from transcripts representing the 1.7-kb subgenomic RNA. Western blot
analysis, using antisera prepared against GST fusion proteins of both
genes, was then used to show that the p8 but not the p9 protein accum
ulated to detectable levels in particulate fractions of infected cells
. Cell-to-cell movement of various MP mutants in Arabidopsis was evalu
ated by in situ hybridization of inoculated leaves. Changes in either
of the two MP genes resulted in failure of the mutants to move cell-to
-cell. Coat protein was found to be unnecessary for cell-to-cell movem
ent Complementation of cell-to-cell movement by cc-inoculating p8-defe
ctive mutants with a p9-defective mutant resulted in delayed systemic
infection. In contrast, efficient cell-to-cell movement was achieved w
hen the MP mutants were inoculated into transgenic plants expressing t
he corresponding functional gene(s). These experiments provide further
evidence that both MP genes encoded by Carmoviruses must function in
trans in the same cell in order to mediate cell-to-cell movement (C) 1
998 Academic Press.