Induction of a proteinase K inhibitor in a potato cultivar with a high degree of field resistance against Phytophthora infestans

FELDMAN M.L.; OLIVA CR; CASALONGUÉ CA; DALEO GR

PHYSIOLOGIA PLANTARUM

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2000 vol. 109 p. 14 - 20

0031-9317

A proteinase K inhibitor (PLPKI) was isolated from a potato cultivar with a high level of field resistance (Solanum tuberosum L. cv. Pampeana INTA), after 24 h of infection with Phytophthora infestans, when inhibitory activity was markedly increased. Purification was performed by heat treatment, gel filtration chromatography and affinity chromatography. A size of 60 kDa was estimated by SDS-PAGE in partially denaturing conditions and by gel filtration. It is multimeric and the monomer has a molecular mass of 8.5?9.0 kDa. PLPKI is highly active against proteinase K (EC 3.4.21.14) but poorly inhibits two serine proteinases of animal origin, trypsin (EC 3.4.21.4) and chymotrypsin (EC 3.4.21.1). A differential expression (determined by activity and immunoblotting assays) of PLPKI was observed between two potato cultivars with different degrees of field resistance to P. infestans. In the resistant cultivar (cv. Pampeana INTA) PLPKI induction (19-fold with respect to healthy leaves) occurred 24 h after infection and remained over basal levels after 48 h infection. By contrast, in the susceptible cultivar (cv. Bintje), no induction was observed.