dTALE approach demonstrates that induction of common bean OVATE Family Protein 7 (PvOFP7) promotes resistance to common bacterial blight.

Abstract

Common bacterial blight of bean (CBB) is a devastating seed-transmitted disease caused by Xanthomonas phaseoli pv. phaseoli and Xanthomonas citri pv. fuscans on common bean (Phaseolus vulgaris L.). The genes responsible for CBB resistance are largely unknown. Moreover, the lack of a reproducible and universal transformation protocol limits the study of genetic traits in common bean. We produced X. phaseoli pv. phaseoli strains expressing artificially-designed Transcription-Activator Like Effectors (dTALEs) to target 14 candidate genes for resistance to CBB based on previous transcriptomic data. In planta assays in a susceptible common bean genotype showed that induction of PvOFP7, PvAP2-ERF71 or PvExpansinA17 expression by dTALEs resulted in CBB symptom reduction. After PvOFP7 induction, in planta bacterial growth was reduced at early colonisation stages and RNA-Seq analysis revealed up-regulation of cell wall formation and primary metabolism, together with major down-regulation of Heat Shock Proteins. Our results demonstrate that PvOFP7 contributes to CBB resistance, and underline the usefulness of dTALEs for functional validation of genes whose induction impacts Xanthomonas-plant interaction.