Isolation and characterization of a polygalacturonase-inhibiting protein from potato leaves. Accumulation in response tosalicylic acid, wounding and infection

A polygalacturonase-inhibiting protein (PGIP) was purified from potato leaves (Solanum tuberosum L. cv. Spunta). The protein was cell wall bound and had a molecular mass of 41 kDa, as determined by sodium dodecyl sulphate-polyacrylamide gel electrophoresis and gel filtration. Potato PGIP showed a broad inhibitory activity against crude polygalacturonase preparations from several fungi grown in liquid culture. Using heterologous antibodies in western blot experiments, it was shown that the levels of PGIP are increased in potato leaves in response to wounding, treatment with salicylic acid and infection with Phytophthora infestans during an incompatible interaction. The data support the hypothesis that synthesis of PGIP may constitute an active defence mechanism of potato plants that is elicited by signal molecules known to induce plant defence genes.