Two coiled-coil regions of Xanthomonas oryzae pv. oryzae harpin differ in oligomerization and hypersensitive response induction.
Hpa1(Xoo) (harpin) is a type III secreted protein of the rice blight bacterial pathogen Xanthomonas oryzae pv. oryzae that elicits a hypersensitive response (HR) in nonhost tobacco. Hpa1(Xoo) is predicted to contain two potential coiled-coil (CC) regions, one at the N-terminus with a high probability of formation, and one at the C-terminus with a lower probability of formation. We constructed several CC-equivalent peptides by a chemosynthetic method, and investigated the structure-function of the predicted Hpa1(Xoo) CC regions, using biophysical and biochemical approaches. Both peptides elicited an HR in tobacco. Mutant versions of the N- and C-terminal peptides that were predicted to disrupt or favor CC formation were generated. The resulting altered HR activity and oligomerization indicated that the N-terminal CC region is essential for eliciting HR, but the C-terminus is not. The results also indicate that a 14-residue fragment (LDQLLCQLISALLQ) within the N-terminal CC region is a minimal and independent functional element for HR-induction in tobacco leaves. We propose that HR-induction requires a specific oligomerization of the CC regions of Hpa1(Xoo).
Department of Plant Pathology, Nanjing Agricultural University, Weigang 1, Nanjing, 210095, People's Republic of China. zhlji@163.com
Zhaolin
Z
Ji
Congfeng
C
Song
Xuzhong
X
Lu
Jinsheng
J
Wang
D000595:Amino Acid Sequence; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry* / Q000235:genetics / Q000276:immunology*; D008969:Molecular Sequence Data; D010935:Plant Diseases / Q000276:immunology / Q000382:microbiology*; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D014026:Nicotiana / Q000276:immunology / Q000382:microbiology*; D014974:Xanthomonas / Q000737:chemistry / Q000235:genetics / Q000276:immunology*
D001425:Bacterial Outer Membrane Proteins