Expression of HpaGXooc protein in Bacillus subtilis and its biological functions.

HpaGXooc, from rice pathogenic bacterium Xanthomonas oryzae pv. oryzicola, is a member of the harpin group of proteins, eliciting hypersensitive cell death in non-host plants, inducing disease and insect resistance in plants, and enhancing plant growth. To express and secret the HpaGXooc protein in Bacillus subtilis, we constructed a recombinant expression vector pM43HF with stronger promoter P43 and signal peptide element nprB. The SDS-PAGE and Western blot analysis demonstrated the expression of the protein HpaGXooc in B. subtilis. The ELISA analysis determined the optimum condition for HpaGXooc expression in B. subtilis WBHF. The biological function analysis indicated that the protein HpaGXooc from B. subtilis WBHF elicits hypersensitive response (HR) and enhances the growth of tobacco. The results of RT-PCR analysis revealed that HpaGXooc induces expression of the pathogenesis-related genes PR-1a and PR-1b in plant defense response.