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POSTERS: Chemical control

Small molecule screening against the secreted “Ca. L. asiaticus” peroxiredoxin, LasBCP, reveals promising chemicals to prevent infection of citrus.
Alejandra Munoz Bodnar - University of Florida. Dean Gabriel- University of Florida, Mukesh Jain- University of Florida

Huanglongbing (HLB) or citrus greening is currently the most devastating bacterial disease of citrus, worldwide. The first host defense response to Ca. L. asiaticus (Las) infection is the oxidative (H2O2) burst. LasBCP (CLIBASIA_RS00445) is non-classically secreted and the gene is conserved in all pathogenic Liberibacters, highly expressed in plant but not expressed in psyllid hosts. When expressed in the culturable L. crescens, LasBCP confers 214-fold more resistance to tert-butyl hydroperoxide (tBOOH) than wild type. When transiently expressed in tobacco, LasBCP suppressed H2O2-mediated transcriptional activation of RbohB and protected against tBOOH-induced peroxidative degradation of lipid membranes, preventing the hypersensitive cell death response. Therefore, LasBCP constitutes a secreted effector protein that likely allows Liberibacter colonization of plant hosts. Denaturing this protein during the initial phases of plant host infection would hypothetically prevent or delay colonization of plants. Two Prestwick combinatorial small molecule libraries representing 1,600 different small molecules were screened for efficacy of thermal denaturation via differential scanning fluorimetry and independently for enzyme inactivation using the Quantitiative Peroxide Assay. Results from both assays revealed 28 chemicals that denatured peroxiredoxin. Based on commercial potential (including cost and potential environmental impact), three chemicals were selected for further evaluation and field trials as preventative treatments for HLB.