Asian Citrus Psyllid RNAi Pathway - RNAi evidence.

Clauvis N T Taning,Wayne B Hunter,Eduardo C Andrade,Olivier Christiaens,Guy Smagghe

doi:10.1038/srep38082

Clauvis N T Taning, Wayne B Hunter + Show 3 more

Open Access

https://doi.org/10.1038/srep38082

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Abstract

Diaphorina citri, known as the Asian citrus psyllid, is an important pest of citrus because it transmits a phloem-limited bacteria strongly implicated in huanglongbing (citrus greening disease). Emerging biotechnologies, such as RNA interference, could provide a new sustainable and environmentally friendly strategy for the management of this pest. In this study, genome and functional analysis were performed to verify whether the RNAi core genes are present in the Asian psyllid genome and if the RNAi machinery could be exploited to develop a management strategy for this pest. Analyses of RNAi-related genes in the Asian citrus psyllid genome showed an absence of sequences encoding R2D2, a dsRNA-binding protein that functions as a cofactor of Dicer-2 in Drosophila. Nevertheless, bioassays using an in Planta System showed that the Asian citrus psyllid was very sensitive to ingested dsRNA, demonstrating a strong RNAi response. A small dose of dsRNA administered through a citrus flush was enough to trigger the RNAi mechanism, causing significant suppression of the targeted transcript, and increased psyllid mortality. This study provides evidence of a functional RNAi machinery, which could be further exploited to develop RNAi based management strategies for the control of the Asian citrus psyllid.

Highlights

Diaphorina citri Kuwayama (Hemiptera: Liviidae)[1] known as the Asian citrus psyllid (ACP), is an important vector which transmits a phloem-limited bacteria (Candidatus Liberibacter asiaticus) strongly implicated in huanglongbing (HLB; citrus greening disease)
All sequences representing the core RNA interference (RNAi) genes were identified in the genome of ACP (Table 1), except R2D2, the cofactor of Dicer-2 in the siRNA pathway
The siRNA pathway is activated by exogenous double-stranded RNA (dsRNA) and involves Dcr2/R2D2 and Ago[2] (RNAi core machinery: siRNA pathway, Table 1)

Summary

Introduction

Diaphorina citri Kuwayama (Hemiptera: Liviidae)[1] known as the Asian citrus psyllid (ACP), is an important vector which transmits a phloem-limited bacteria (Candidatus Liberibacter asiaticus) strongly implicated in huanglongbing (HLB; citrus greening disease). Dependence upon intensive insecticide applications to reduce pathogen spread by ACP feeding has resulted in psyllids developing pesticide resistance[5] Emerging biotechnologies, such as RNA interference (RNAi), using natural gene-based targeting could provide a new sustainable and environmentally friendly management of ACP, and other insect pests of citrus. In silico genome analysis were performed on the ACP genome to identify core RNAi-related genes known to play key roles in small non coding RNA pathways This was followed by functional studies based on oral bioassays performed on adult ACP, in order to confirm that the RNAi machinery was functional. The results of this study provide valuable ground information for future studies on the efficacy of RNAi for the control of ACP, as well as for conducting further genome-wide screens to identify genes that could be used for the development of pest management methods against ACP

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