The classical arabinogalactan protein gene family of arabidopsis

Arabinogalactan proteins (AGPs) are extracellular proteoglycans implicated in plant growth and development. We searched for classical AGPs in Arabidop sis by identifying expressed sequence tags based on the conserved domain st ructure of the predicted protein backbone. To confirm that these genes enco ded bona fide AGPs, we purified native AGPs and then deglycosylated and deb locked them for N-terminal protein sequencing. In total, we identified 15 g enes encoding the protein backbones of classical AGPs, including genes for AG peptides-AGPs with very short backbones (10 to 13 amino acid residues). Seven of the AGPs were verified as AGPs by protein sequencing. A gene encod ing a putative cell adhesion molecule with AGP-like domains was also identi fied. This work provides a firm foundation for beginning functional analysi s by using a genetic approach.