THE PLANT CELL, Vol 7, Issue 12 2211-2225, Copyright © 1995 by American Society of Plant Biologists
Extensin-like Glycoproteins in the Maize Pollen Tube Wall
A. L. Rubinstein, J. Marquez, M. Suarez-Cervera and P. A. Bedinger
Biology Department, Colorado State University, Fort Collins, Colorado 80523
We recently described the cloning and characterization of Pex1, a maize
pollen-specific gene with an extensin-like domain. Here, we report that
antibodies raised against a Pex fusion protein and a Pex synthetic peptide
recognize a protein doublet with an apparent molecular mass of ~300 kD as
well as larger proteins in pollen extracts. These proteins were not
detected in extracts of seedling, endosperm, ear, silk, root, leaf, wounded
leaf, meiotic tassel, or young microspore. After deglycosylation, only the
protein doublet was detected by the anti-Pex antiserum, suggesting that the
higher molecular mass proteins represent a glycosylated form of the Pex
proteins. The anti-Pex antiserum was also used in immunolocalization
experiments with in vitro-germinated pollen. With the aid of a confocal
light microscope, the Pex proteins were localized to the pollen tube wall.
The Pex proteins could not be removed with high salt, SDS, or chaotropic or
reducing agents, suggesting a very tight association with the pollen tube
wall. Immunocytochemical analysis at the ultrastructural level localized
the Pex proteins to the intine in mature pollen and to the callosic sheath
of the pollen tube wall in germinated pollen. Localization to the pollen
tube wall strongly suggests that the Pex proteins play a role in pollen
tube growth during pollination.
