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N.benthamiana as a surrogate host for studying the pathogenicity of A.citrulli, the causal agent of bacterial fruit blotch of cucurbits

Merve Kiremit: Virginia Tech

<div><em>Acidovorax citrulli</em> is the causal agent of bacterial fruit blotch (BFB) of cucurbits<em>.</em> Despite its significant agricultural importance, the mechanisms associated with <em>A. citrulli</em> pathogenicity have not been extensively investigated. In this study, we used <em>Nicotiana benthamiana</em> and <em>Nicotiana tabacum</em> as surrogate hosts for studying <em>A. citrulli</em> virulence and nonhost resistance triggered by bacterial type III-secreted effectors. Two <em>A. citrulli</em> strains, M6 and AAC00-1, that represent the two major groups among <em>A. citrulli </em>populations, induced disease symptoms on <em>N. benthamiana</em>, but triggered hypersensitive response (HR) on <em>N. tabacum </em>plants. Transient expression of 19 T3S effectors in <em>N. benthamiana</em> and <em>N. tabacum </em>leaves revealed that three effectors, Aave1548, Aave2708, and Aave2166, could trigger water-soaking-like cell death in <em>N. benthamiana</em> and HR in <em>N. tabacum</em>. Knockout effector gene <em>Aave1548</em> in strains M6 and AAC00-1 reduced <em>A. citrulli</em> virulence on <em>N. benthamiana</em> and melon (<em>Cucumis melo</em> L.). Transient expression Aave1548 and Aave2166 effectors triggered nonhost HR in <em>N. tabacum</em>, and this reaction depends on the functionality of the immune signaling component, <em>NtSGT1</em>.</div>