FIG. 7.
Hypersensitive reaction of the purified Hpa1 protein of X. oryzae pv. oryzicola. A. A 12.5% SDS-polyacrylamide gel showing Hpa1 that was expressed and purified from E. coli (BL21). Two bands are apparent in lane 1, while only one band is apparent in lane 2 after treatment of the protein with 0.5 M Tris(hydroxypropyl)phosphine (Novagen), suggesting that the higher-Mr band is a dimer due to cysteine cross-linking. B. Comparison of Hpa1 activity with that of well-known harpin HrpN. 1, BL21 harboring empty vector pET21a; 2, RS105 (108 CFU/ml); 3, Hpa1 (1 μg/ml); 4, HrpN (5 μg/ml) (kindly provided by Z. Wei, Eden Biotech). The tobacco leaves were photographed 24 h after injection using needleless syringes. Three replicates of the assay were conducted. The first lane in panel A is the protein marker.