Molecular Characterization of the Rice Pathogenesis-related Protein, OsPR-4b, and Its Antifungal Activity Against Rhizoctonia solani

We cloned and identified a new rice pathogenesisrelated (PR)-4 gene, OsPR-4b. OsPR-4b encodes a 151 amino acid protein with a predicted molecular mass of 16.47 kDa and pI of 4.42. The putative OsPR-4b shows high similarity to PR-4 type proteins from various plant species and belongs to the Barwin family. Like other PR-4s from monocot plants, OsPR-4b contains a conserved Barwin domain and has a signal peptide at its N-terminus. Recombinant OsPR-4b protein expressed in Escherichia coli showed antifungal activity in vitro against the sheath blight fungus, Rhizoctonia solani. The results suggest that the OsPR-4b may play a role in the disease resistance responses of rice against pathogen attacks through its antifungal activity.