PURIFICATION OF POTATO LEAF PLASMA-MEMBRANE PROTEIN PP34, A PROTEIN PHOSPHORYLATED IN RESPONSE TO OLIGOGALACTURONIDE SIGNALS FOR DEFENSE AND DEVELOPMENT

A potato (Solanum tuberosum L) plasma membrane protein called pp34, th e only known example of a plasma membrane protein that is phosphorylat ed specifically in response to defined oligogalacturonide signals in p lants, has been purified to apparent homogeneity. Polyclonal antibodie s raised in rabbits against the purified pp34 protein immunoprecipitat ed a single thiophosphorylated protein species from potato plasma memb ranes, as analyzed by two-dimensional denaturing electrophoresis and f luorography. The pp34 antibodies also recognized a single protein in t omato (Lycopersicon esculentum L.) membranes that is thiophosphorylate d in response to oligogalacturonide elicitors, as demonstrated by west ern blotting and specific immunoprecipitation. These experiments confi rm the identity of the tomato membrane protein as a pp34 homolog and e stablish the high monospecificity of the pp34 antibodies. This will pe rmit further investigation of the role of protein phosphorylation in o ligouronide signaling for defensive genes in potato and tomato plants.