Abstract: Harpins protein expressed by hypersensitive response and pathogenity gene(hrp) can induce the defense response of plant to diseases and insect pests of plant. By the way of agar solid plate, Erwinia carotovora pv. carotovora strain Ecc36 can produce high levels of extracellular enzymes. The Ecc36 strain could elicit the hypersensitive response(HR) in tobacco leaves. These results showed that some kind of hrp was in Ecc36 strain. Southern Blot analysis of Ecc36 with a hrpN gene probe labeled by DIG-dUTP showed that the Ecc36 strain possesses hrpN gene,named hrpN_EccPR. Through nucleotide sequence analysis,a 1 254 bp open reading frame(ORF) of Ecc36 hrpN was revealed. A Harpin protein(named HrpN_EccPR protein) encoded by hrpN_EccPR comprise 417 amino acid residues with 45.27 ku and pI 5.73 approximately. The deduced amino acid sequence of Ecc36 hrpN shares high homology with Harpin proteins of several other E. carotovora strains. The hrpN_EccPR gene was cloned into vector pET28a(+) for expression,and then transferred into the cells of E. coli strain BL21(DE3). The HrpN_EccPR protein was overexpressed in reconstructed BL21(DE3) when the strain was induced by IPTG. The purified HrpN_EccPR effectively elicits the HR in tobacco leaves. Those show HrpN_EccPR protein has the biological activity of stimulating the immune response of plants,and provide for further study on the mechanism of the defense response induced by HrpN_EccPR protein in plant.

Key words: HrpN_EccPR protein, Gene cloning, hrpN gene, Erwinia carotovora, Hypersensitive response (HR)

CLC Number: 

• S432.2

• Q78