Cloning of the ParA1 Gene from Phytophthora parasitica and Its Expression in Escherichia coli
寄生疫霉parA1基因的克隆及在大肠杆菌中的表达

Elicitins are a family of small proteins secreted by species of the genus Phytophthora and Pythium. They can cause a hypersensitive response (HR) and induce systemic acquired resistance (SAR) in tobacco. Here we report cloning and characterization of parA1 homologs from 4 strains of Phytophthora parasitica isolated from tobacco and locust in China. Amplification by PCR (polymerase chain reaction) of DNA from the 4 strains, using primers specific to a parA1 reported previously, produced 4 products. Their nucleotide sequences are highly conserved and identical to the parA1 gene previously cloned. Therefore,the parA1 genes were successfully cloned from the Chinese strains of P. parasitica. They were cloned into the vector pET-30a (+) and transformed into Escherichia coli BL21. The expressed product was biologically active, as it caused HR in tobacco leaf panels after direct infiltration; the protein was thermostable and sensitive to protease K. We have established a recombinant E. coli that produces the elicitin. This is the first report of cloning of parA1 genes from locust isolate of the pathogen.