EXTENSIN-LIKE GLYCOPROTEINS IN THE MAIZE POLLEN-TUBE WALL

We recently described the cloning and characterization of Pex1, a maiz e pollen-specific gene with an extensin-like domain, Here, we report t hat antibodies raised against a Per fusion protein and a Per synthetic peptide recognize a protein doublet with an apparent molecular mass o f similar to 300 kD as well as larger proteins in pollen extracts, The se 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 an ti-Per antiserum, suggesting that the higher molecular mass proteins r epresent a glycosylated form of the Per proteins, The anti-Per antiser um was also used in immunolocalization experiments with in vitro-germi nated pollen, With the aid of a confocal light microscope, the Per pro teins were localized to the pollen tube wall, The Per proteins could n ot be removed with high salt, SDS, or chaotropic or reducing agents, s uggesting a very tight association with the pollen tube wall. Immunocy tochemical analysis at the ultrastructural level localized the Per pro teins to the intine in mature pollen and to the callosic sheath of the pollen tube wall in germinated pollen, Localization to the pollen tub e wall strongly suggests that the Per proteins play a role in pollen t ube growth during pollination.