THE PLANT CELL, Vol 9, Issue 2 145-156, Copyright © 1997 by American Society of Plant Biologists
The Maize Pathogenesis-Related PRms Protein Localizes to Plasmodesmata in Maize Radicles
I. Murillo, L. Cavallarin and B. S. Segundo
Departamento de Genetica Molecular, Centro de Investigacion y Desarrollo de Barcelona, Consejo Superior de Investigaciones Cientificas, Jordi Girona 18, 08034 Barcelona, Spain
Pathogenesis-related (PR) proteins are plant proteins induced in response
to infection by pathogens. In this study, an antibody raised against the
maize PRms protein was used to localize the protein in fungal-infected
maize radicles. The PRms protein was found to be localized at the contact
areas between parenchyma cells of the differentiating protoxylem elements.
By using immunoelectron microscopy, we found that these immunoreactive
regions correspond to plasmodesmal regions. This was also true for the
parenchyma cells filling the central pith of the vascular cylinder,
although PRms mRNA accumulation was not detected in these cells. These
findings suggest that for one cell type, the parenchyma cells of the
central pith, the protein is imported rather than synthesized. The
localization of the PRms protein indicates the possible existence of
mechanisms for sorting of plant proteins to plasmodesmata and suggests that
this protein may have a specialized function in the plant defense response.
These findings are discussed with respect to the structure and function of
plasmodesmata in cell-to-cell communication processes in higher plants.
