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

Abstract

Phytophthora capsici is a broad-host-range oomycete pathogen, which can cause severe phytophthora blight disease of pepper and hundreds of other plant species worldwide. Natural resistance against P. capsici is inadequate, and it is very difficult to control by most of existing chemical fungicides. Therefore, it is urgent demand to develop alternative strategies to control this pathogen. Recently, host-induced or spray-induced gene silencing of pathogen’s essential or virulent genes provided an effective strategy for disease controls. Here, we demonstrated that P. capsici could effectively take up siRNAs from environment. According to RNA-seq and qRT-PCR analysis, we identified four P. capsici RXLR effector genes that are significantly up-regulated during the infection stage. Transient over-expression and promote infection assays indicated that RXLR1 and RXLR4 could promote the pathogen’s infection. Using VIGS system in pepper plants, we found that in planta expressing RNAi construct that target RXLR1 or RXLR4 could significantly reduce the pathogen’s infection, while co-interfering RXLR1 and RXLR4 could confer a more enhanced resistance to P. capsici. We also found that exogenous applying siRNAs that target RXLR1 or RXLR4 could restrict growth of P. capsici on the pepper and Nicotiana benthamiana leaves; when targeting RXLR1 and RXLR4 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 P. capsici and also provides an important basis for the development of RNA-based anti-oomycete agents.

Functionalized Carbon Dot‐Delivered RNA Nano Fungicides as Superior Tools to Control Phytophthora Pathogens through Plant RdRP1 Mediated Spray‐Induced Gene Silencing

“…[ 12a ] Furthermore, it has been confirmed that exogenous 24‐nt siRNA duplexes rather than 151‐nt dsRNA duplexes can be effectively absorbed by P. capsici . [ 42 ] Herein, we discovered that dsRNA‐sprayed plants could efficiently induce gene silencing in P. capsici but dsRNAs directly sprayed onto P. capsici could not. All these evidences further confirms that the pathosystem is crucial for dsRNA‐derived sRNA generation and successful SIGS against Phytophthora .…”

Endophytic Bacillus subtilis H17‐16 effectively inhibits Phytophthora infestans, the pathogen of potato late blight, and its potential application

“…A conserved CRN effector of Phytophthora sojae , CRN78, has been reported to enhance its virulence on host plants 68 . RNA interference (RNAi) targeting RXLR1 or RXLR4 in Phytophthora capsici significantly reduced the infestation of pepper by the pathogen 69 . After H17‐16 treatment, the number of DEGs related to virulence was large, with 97 CRN and 66 RXLR effector genes.…”

Extracellular RNA: mechanisms of secretion and potential functions

“…Consistent with this, no extracellular RNases capable of cleaving dsRNA have been identified in plants ( MacIntosh and Castandet, 2020 ). It has been shown that several plant pathogens can take up short and long ss- and dsRNAs directly from the environment ( M. Wang et al , 2016 ; Qiao et al , 2021 ; Cheng et al , 2022 ), probably by the endocytic pathway ( Wytinck et al , 2020a , b ). This suggests that extravesicular sRNAs could also undergo cross-kingdom trafficking.…”