Two coiled-coil regions of <Emphasis Type="Italic">Xanthomonas oryzae</Emphasis> pv. <Emphasis Type="Italic">oryzae</Emphasis> harpin differ in oligomerization and hypersensitive response induction |
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Authors: | Zhaolin Ji Congfeng Song Xuzhong Lu Jinsheng Wang |
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Institution: | (1) Department of Plant Pathology, Nanjing Agricultural University, Weigang 1, Nanjing, 210095, People’s Republic of China;(2) Rice Research Institute, Anhui Academy of Agricultural Sciences, Nongke South Road 40, Hefei, 230031, People’s Republic of China |
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Abstract: | Hpa1Xoo (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. Hpa1Xoo 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 Hpa1Xoo 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 Hpa1Xoo. |
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