MONOCLONAL-ANTIBODIES TO BARLEY ALEURAIN AND HOMOLOGS FROM OTHER PLANTS

Barley aleurain is contained within a specific type of vacuole charact erized by acidic pH and the presence of other hydrolytic enzymes. The aleurain-containing vacuole is distinct from protein storage vacuoles, and anti-aleurain antibodies serve as markers for this organelle in b arley cells. Aleurain is a unique type of cysteine protease, and other plant species have genes for homologs whose sequences are highly cons erved, but little is known about these homologs at the protein level. Seven monoclonal antibodies to barley aleurain were isolated, which bi nd to and define aleurain homologues in Arabidopsis, Petunia, and toba cco cell extracts. Interestingly, in addition to 29-32 kDa aleurain ho mologs, Petunia extracts contain a protein of similar to 50 kDa and to bacco extracts a protein of similar to 40 kDa that are recognized by m ultiple different monoclonal antibodies, indicating an unexpected dive rsity to the aleurain protein family. Among the group of antibodies ar e some that efficiently immunoprecipitate metabolically labeled aleura in from barley cell extracts, and some that efficiently label aleurain in immunofluorescence assays using root tip cells. These antibodies s hould be useful for plant cell biologists who study vacuole biogenesis and function and sorting of proteins to specific vacuolar compartment s, in barley as well as other plant species.