RNAi-Based Gene Silencing of RXLR Effectors Protects Plants Against the Oomycete Pathogen .

is a broad-host range oomycete pathogen that can cause severe phytophthora blight disease of pepper and hundreds of other plant species worldwide. Natural resistance against is inadequate, and it is very difficult to control by most of existing chemical fungicides. Therefore, it is urgent to develop alternative strategies to control this pathogen. Recently, host-induced or spray-induced gene silencing of essential or virulent pathogen genes provided an effective strategy for disease controls. Here, we demonstrate that can effectively take up small interfering RNAs (siRNAs) from the environment. According to RNA-seq and quantitative reverse transcription PCR analysis, we identified four RXLR effector genes that are significantly up-regulated during the infection stage. Transient overexpression and promote-infection assays indicated that RXLR1 and RXLR4 could promote pathogen infection. Using a virus-induced gene silencing system in pepper plants, we found that in planta-expressing RNA interference (RNAi) constructs that target or could significantly reduce pathogen infection, while co-interfering and could confer a more enhanced resistance to . We also found that exogenously applying siRNAs that target or could restrict growth of on the pepper and leaves; when targeting and simultaneously, the control effect was more remarkable. These data suggested that RNAi-based gene silencing of RXLR effectors has great potential for application in crop improvement against and also provides an important basis for the development of RNA-based antioomycete agents.[Formula: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.