Effector Gene xopAE of Xanthomonas euvesicatoria 85-10 Is Part of an Operon and Encodes an E3 Ubiquitin Ligase

Abstract

Xanthomonas bacteria utilize a type III secretion system to cause disease in many crops. This study provides insights into the evolution, translocation, and biochemical function of the XopAE type III secreted effector, contributing to the understanding of Xanthomonas -host interactions. We establish XopAE as a core effector of seven Xanthomonas species and elucidate the evolution of the Xanthomonas euvesicatoria xopAE locus, which contains an operon encoding a truncated effector. Our findings indicate that this operon evolved from the split of a multidomain gene into two ORFs that conserved the original domain function. Analysis of xopAE 85-10 translation provides the first evidence for translation initiation from an ATT codon in Xanthomonas . Our data demonstrate that XopAE 85-10 is an XL box E3 ubiquitin ligase and provide insights into the structure and function of this effector family.