Abstract:

The Harpins produced by two pathovars(pv. oryzae and pv. oryzicola) of Xanthomonas oryzae are different from the reported harpins. The recombinant E.coli strains HRF1 and HRF2 harbored hrf1 gene of pv. oryzae and hrf2 gene of pv. oryzicola, respectively. After induced by IPTG, the Cell Free Crude Solution(CFCS) of hrf1 and hrf2 can elicit hypersensitive reaction(HR) on tobacco leaves. Precipitated CFCS with(NH₄)₂SO₄(30%—60%), purified with HiPrep Q XL ion exchange and Mini prepared NativePAGE(10%), two single bands with molecular weights of 15 600 and 15 300, and about pI=4.5 were respectively obtained. The results show the same characteristics to other Harpins: elicit HR, induce TMV resistance on tobacco leaves, sensitive to protease K and stable to heat. Their biological activity can be inhibited by eucaryota metabolic inhibitors(cycloheximide, actinomycin D and LaCl₃). Meanwhile, serological experiments of the proteins with ODD indicate that cross reactions have occurred in two Harpins from pv.oryzae and pv.oryzicola.