Poster: Plant-pathogen interactions
Abs #
514: Induction of the hypersensitive response in Nicotiana benthamiana by Erwinia amylovora and genetic evidence for EopB as an HR suppressor
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Presenter: |
Oh, Chang-Sik , co35@cornell.edu |
Authors | Oh, Chang-Sik (A) Beer, Steven V. (A) | | Affiliations: |
(A): Department of Plant Pathology, Cornell University
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Erwinia amylovora induces a hypersensitive response (HR) in nonhost plants like tobacco and secretes HrpN, HrpW and DspE through a Hrp type III secretion pathway. Previous data showed that HrpN and HrpW, but not DspE, are involved in HR induction in tobacco, N. tabacum cv. Xanthi. HR induction was re-examined in N. benthamiana using three different bacterial systems for delivery and induction. HrpN with a signal peptide and DspE separately induced clear HRs in N. benthamiana when the genes were expressed transiently. The HR induced by HrpN, but not by DspE, was inhibited by AvrPtoB, a known HR suppressor, suggesting that the two proteins induce the HR through different pathways. Escherichia coli strain MC4100, carrying genes for the Hrp type III secretion pathway of E. amylovora, and both hrpN and dspE, induced an HR in N. benthamiana. While the HR was induced by E. amylovora mutated singly in hrpW, hrpN or dspE within 24 hours after infiltration, a strain with mutations in both hrpN and dspE lacked HR-inducing activity, indicating that both HrpN and DspE are necessary for HR elicitation in N. benthamiana. However, a mutant from which ca. 12-kb of DNA was deleted, including hrpN, dspE and five intervening genes including eopB, a yopJ homolog, elicited a clear HR. When the deletion mutant was complemented with eopB, and its putative chaperone orfA, or with avrPtoB, the HR was much reduced in extent and intensity, indicating that an unknown factor X also can elicit the HR in N. benthamiana and that both EopB and AvrPtoB inhibit HR elicitation by X. Thus, at least three different factors, HrpN, DspE, and X can induce the HR through different pathways in N. benthamiana. Furthermore, EopB can function as an HR suppressor.
