A style-specific hydroxyproline-rich glycoprotein with properties of both extensins and arabinogalactan proteins

A basic, hydroxyproline-rich glycoprotein (molecular mass 120 kDa) has been purified from the styles of Nicotiana alata. An antibody, specific for the protein backbone (molecular mass 78 kDa) of the glycoprotein, was used to demonstrate that the glycoprotein is a soluble, style-specific component and that related molecules are present in the styles of other solanaceous species. Linkage analysis of the carbohydrate portion of the glycoprotein, together with antibody binding studies, indicates that the glycoprotein contains both extensin-like and arabinogalactan-protein (AGP)-like side chains. Furthermore, the AGP-like side-chains contain a style-specific epitope that is also present on AGPs from N. alata styles and glycoconjugates from the styles of other members of the Solanaceae. The abundance of this 120 kDa glycoprotein, its location in the extracellular matrix of the transmitting tract and its conservation in several species within the Solanaceae suggests a role in pistil function.