No abstract

Phytocystatins are plant-derived cysteine proteinase inhibitors implicated in the endogenous regulation of protein turnover and defense mechanisms against insects and pathogens. A cysteine proteinase inhibitor, PgCPI, was isolated and characterized from Panax ginseng. Sequence analysis revealed that the coding cDNA sequence of PgCPI is 609 base pairs in length with a predicted molecular mass of 22.5 kDa. A GenBank BlastX search revealed that the deduced amino acid sequence of PgCPI shares a highdegree homology with cysteine proteinase inhibitors from other plants. In this present study, we analyzed the expression patterns of PgCPI against various abiotic and biotic stresses at different time points using quantitative real time-PCR. Enzymatic activity of PgCPI was also determined against cysteine proteinase. Our results reveal that PgCPI is moderately induced by NaCl, chilling, CuSO 4 , ABA, and jasmonic acid. However, high light, UV, MeJA, and wounding triggered a significant induction (more than fourfold) of PgCPI within 12-h post-treatment, especially PgCPI prominently accumulated by wounding (24-fold). In addition, increased transcripts of PgCPI were investigated in fungal-and nematode-infected roots. These results suggest that PgCPI is involved in defense responses to biotic and abiotic stresses.