Isolation and characterization of a polygalacturonase-inhibiting protein from potato leaves. Accumulation in response to salicylic acid, wounding andinfection

A polygalacturonase-inhibiting protein (PGIP) was purified from potato leav es (Solanum tuberosum L. cv. Spunta). The protein was cell wall bound and h ad a molecular ma ss of 41 kDa, as determined by sodium dodecyl sulphate-po lyacrylamide gel electrophoresis and gel filtration. Potato PGIP showed a b road inhibitory activity against crude polygalacturonase preparations from several fungi grown in liquid culture. Using heterologous antibodies in wes tern blot experiments, it was shown that the levels of PGIP are increased i n potato leaves in response to wounding, treatment with salicylic acid and infection with Phytophthora infestans during an incompatible interaction. T he data support the hypothesis that, synthesis of PGIP may constitute an ac tive defence mechanism of potato plants that is elicited by signal molecule s known to induce plant defence genes. (C) 2001 Editions scientifiques et m edicales Elsevier SAS.