Cloning of Proteinase Inhibitor Gene StPI in Diploid Potato and Its Expression Analysis

A full-length cDNA of proteinase inhibitor gene with completed open reading frame of 116 amino acids was cloned from Ralstonia solanacearum (Rs) resistant potato leaves using the rapid amplification of cDNA ends (RACE) method and designated as StPI. BLAST search against NCBI showed that the StPI gene shared 89% identity with potato proteinase inhibitor I precursor in nucleotide and 74% in amino acid. Analysis of semi-quantitative RT-PCR indicated that this gene was induced by Rs as well as up-regulated by jasmonic acid (JA). The StPI gene expression reached the highest level during 6–12 h post Rs-inoculation or JA-treatment, and then leveled off. Moreover, this gene was strongly induced by JA and its mRNA accumulation increased more quickly than that of Rs-inoculation. The StPI gene may play a role in potato resistance against Rs. The induction of StPI by Rs invasion may have a similar signal transduction pathway with JA treatment.