The small GTPase NtRHO1 negatively regulates tobacco defense response to Tobacco mosaic virus by interacting with NtWRKY50.

Small GTPases play critical roles in the regulation of plant growth and development. However, the mechanism of small GTPases in plant response to virus infection remains largely unknown. Here, a Rho-type GTPase NtRHO1 was identified as one of up-regulated genes after tobacco mosaic virus (TMV) infection. Subcellular localization of NtRHO1 showed that it was localized in the cytoplasm, plasma membrane as well as nucleus. Transient overexpression of NtRHO1 in Nicotiana benthamiana plants accelerated virus reproduction and led to more reactive oxygen species production. By contrast, silencing of NtRHO1 reduced the sensitivity of N. benthamiana plants to TMV-GFP. Further explorations showed that there existed a direct interaction between NtRHO1 and NtWRKY50, a positive regulator of N. benthamiana plants response to virus infection. Yeast one-hybrid and electrophoretic mobility shift assays showed that this regulation was related to NtWRKY50's binding capacity to the WK-box of PR1 promoter, which was weakened by the interaction between NtRHO1 and NtWRKY50. Thus, the role of a novel small GTPase NtRHO1 in the plant-pathogen interaction was explored and its mechanism was proposed.