Small GTPases play critical roles in the regulation of plant growth and development. However, the mechanism of action of small GTPases in plant response to virus infection remains largely unknown. Here, the gene encoding a Rho-type GTPase, NtRHO1, was identified as one of the genes up-regulated after tobacco mosaic virus (TMV) infection. Subcellular localization of NtRHO1 showed that it was located in the cytoplasm, plasma membrane, and nucleus. Transient overexpression of NtRHO1 in Nicotiana benthamiana accelerated TMV reproduction and led to the production of reactive oxygen species. By contrast, silencing of NtRHO1 reduced the sensitivity of N. benthamiana to TMV-GFP. Further exploration revealed a direct interaction between NtRHO1 and NtWRKY50, a positive regulator of the N. benthamiana response to virus infection. Yeast one-hybrid and electrophoretic mobility shift assays showed that this regulation was related to the capacity of NtWRKY50 to bind to the WK-box of the PR1 promoter, which was weakened by the interaction between NtRHO1 and NtWRKY50. Thus, our results indicate that the small GTPase NtRHO1 plays a negative role in tobacco response to TMV infection by interacting with transcription factor NtWRKY50, resulting in reduced plant immunity.

中文翻译：

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小 GTPase NtRHO1 通过与 NtWRKY50 相互作用负调节烟草对烟草花叶病毒的防御反应


小 GTP 酶在植物生长和发育的调节中发挥着关键作用。然而，小 GTP 酶在植物对病毒感染的反应中的作用机制仍然很大程度上未知。在此，编码 Rho 型 GTP 酶的基因 NtRHO1 被鉴定为烟草花叶病毒 (TMV) 感染后上调的基因之一。 NtRHO1的亚细胞定位表明它位于细胞质、质膜和细胞核中。 NtRHO1 在本塞姆氏烟草中的瞬时过度表达加速了 TMV 繁殖并导致活性氧的产生。相比之下，NtRHO1 的沉默降低了本塞姆氏烟草对 TMV-GFP 的敏感性。进一步的探索揭示了 NtRHO1 和 NtWRKY50 之间的直接相互作用，NtWRKY50 是本塞姆氏烟草对病毒感染反应的正调节因子。酵母单杂交和电泳迁移率变动分析表明，这种调节与 NtWRKY50 结合 PR1 启动子 WK-box 的能力有关，而 NtRHO1 和 NtWRKY50 之间的相互作用会削弱这种能力。因此，我们的结果表明，小GTP酶NtRHO1通过与转录因子NtWRKY50相互作用，在烟草对TMV感染的反应中发挥负面作用，导致植物免疫力降低。