Mind the gap : Analysis of Tsw resistance against tospoviruses

Abstract

Tospoviruses are among the most important plant pathogens and cause serious crop losses worldwide. Tospoviruses have evolved to smartly utilize the host cellular machinery to accomplish their life cycle. Plants mount two layers of defense to combat their invasion. The first one involves the activation of an antiviral RNA interference (RNAi) defense response. However, tospoviruses encode an RNA silencing suppressor that enables them to counteract antiviral RNAi. To further combat viral invasion, plants also employ intracellular innate immune receptors (e.g., Sw-5b and Tsw) to recognize different viral effectors (e.g., NSm and NSs). This leads to the triggering of a much more robust defense against tospoviruses called effector-triggered immunity (ETI). Tospoviruses have further evolved their effectors and can break Sw-5b-/Tsw-mediated resistance. The arms race between tospoviruses and both layers of innate immunity drives the coevolution of host defense and viral genes involved in counter defense. In this review, a state-of-the-art overview is presented on the tospoviral life cycle and the multilined interplays between tospoviruses and the distinct layers of defense.