Abstract
Studies were performed to investigate the changes of potato pathogenesis-related proteins (PRPs) upon infection with late blight pathogen. Obtained data showed that in both resistant and susceptible potato cultivars, inoculated leaves with Phytophthora infestans showed a significantly higher amount of total protein than the healthy ones. In a bioassay experiment, the crude protein extracted from leaves of resistant potato cultivars showed the lowest, while those from susceptible ones indicated the highest fungal growth. SDS-PAGE analysis of acidic soluble proteins extracted from inoculated potato leaves at different periods of inoculation with P. infestans showed that nine proteins with molecular weight ranged from 12-45 kDa were increased gradually with time. RT-PCR analysis showed that in spite of the variation between tested potato cultivars in their resistance to late blight disease, the gene encoding osmotin-like protein (OSM-1 gene) existed at DNA level. At RNA level, an induction of OSM-1 gene expression was detected potato cultivars after inoculation with P. infestans. The expression of OSM-1 gene in the resistant cultivar occurred earlier (6 hpi) and stronger, while being induced later in the susceptible cultivar. Earlier and higher accumulation of PRPs in the resistant cultivars suggested that they were related to the defense mechanism against P. infestans. (C) 2010 Friends Science Publishers