T3SS-effectors of Xanthomonas oryzae pv. oryzae: The arsenal to bout rice immunity for bacterial blight development

Abstract

Xanthomonas oryzae pv. oryzae (Xoo), the bacterial blight (BB) pathogen employs T3SS-effectors of two classes Xanthomonas Outer protein (Xop) and Transcriptional Activational-Like (TAL) effectors to undermine rice PTI for its limitless proliferation inside the rice during disease development. The TALEs include both complete (tTALEs) as well as incomplete or pseudo/iTALEs. Xoo mutants lacking these effectors functional genes when inoculated on rice caused significant increased expression of rice PTI genes. The both the effectors are tracked to localize to the rice plasma membrane. The effectors secreted in phase manner are targeted to nullify the innate and induced defense response in the host. The immune suppression is mediated through enzymatic and transcriptional function of these effectors. In short analysis, Xop effectors put-off of triggered immunity whereas TAL effectors ensure the supply of required nutrients for the bacteria. In vice-versa, these effectors are recognition factors for induction of defense response in non/resistant hosts which of importance in the exploitation of these factors for improving the resistance of rice against the Xoo. This advocates that Xoo T3 effectors interacts with the host interactors to accomplish its common goal of undermining the plant immunity, either through interfering physiological function or through weakening plant immune protection system. This review highlights the recent understanding into the Xoo-effectors vs rice that opened up novel rice targets and their sensible exploitation could lead to broad spectrum resistance to BB of rice.