Xanthomonas euvesicatoriaeffectorXeAvrRxo1 triggers a Rxo1-mediated defense response inNicotiana benthamianaand its chaperone Xe4429 functions as an antitoxin, an expression repressor, and an enhancer ofXeAvrRxo1 secretion

Abstract

SummaryXanthomonas euvesicatoria(X. euvesicatoria) is the causal agent of bacterial spot disease that threatens pepper and tomato production around the globe.X. euvesicatoriageneXe4428encodes a type III effector (T3E) that shares 89.67% amino acid identity withXanthomonas oryzaepv.oryzicola(Xoc) T3E AvrRxo1. Deletion ofXe4428in the genome ofX. euvesicatoria(strain Xcv85-10) compromised its virulence to infect pepper andNicotiana benthamianaplants. Transient co-expression of Xe4428 andRxo1on pepper andN. benthamianaplant leaves results in a robust hypersensitive reaction. Thus, Xe4428, renamed asXeAvrRxo1, is a bona fide orthologue ofXocAvrRxo1 that possesses both virulence and avirulence functions. Expression ofXeAvrRxo1 inE. coliandX. euvesicatoriais toxic to both bacterial cells. AnotherX. euvesicatoriageneXe4429, encodes a putative chaperone ofXeAvrRxo1, which can interact with XeAvrRxo1 to suppress its toxicity inX. euvesicatoriaandE. colibacterial cells. Xe4429 also binds to the promoter region ofXeavrRxo1and represses its transcription/translation inX. euvesicatoriabacterial cells. In addition, expression of Xe4429 can enhance the secretion and translocation ofXeAvrRxo1 into plant cells. Therefore, Xe4429 functions as an antitoxin, a transcription repressor, and a type III chaperone that is capable of enhancing the secretion and translocation ofXeAvrRxo1 during pathogenesis.