Expression of dsRNA in recombinant Isaria fumosorosea strain targets the TLR7 gene in Bemisia tabaci

Abstract

BackgroundRNA interference (RNAi) technology shows a great potential in controlling agricultural pests, despite the difficulty of introducing exogenous dsRNA/siRNA into target pests. Isaria fumosorosea is a common fungal pathogen of the B-biotype Bemisia tabaci (whitefly), which is a widespread pest. Entomopathogenic fungi directly penetrate the cuticle and invade insect hemocoel. Application of I. fumosorosea expressing dsRNA of whitefly immunity-related gene may aid in developing RNAi technology to effectively control whiteflies.MethodsA dsRNA expression plasmid, psTLR7, was constructed by introducing the Toll-like receptor 7 (TLR7) gene of B-biotype whitefly to the silent vector, pSilent-1. The plasmid psTLR7 was transferred into the protoplast of the I. fumosorosea strain IfB01. Then, the recombinant strain was screened out based on the biological stability and bioactivity against whitefly.ResultsA genetically stable recombinant strain IfB01-TRL7 was screened out. The impact of IfB01-TRL7 against whitefly TRL7 gene was validated by qPCR. Lower expression levels of the TLR7 gene was observed in the whiteflies infected by the recombinant strain. The bioassay results indicated that compared to IfB01 strain, IfB01-TRL7 increased the mortality of whitefly nymphs, and decreased and shortened the values of LC50 and LT50, thus indicating higher virulence of IfB01-TRL7.ConclusionThe expression of the dsRNA of whitefly TLR7 gene in recombinant I. fumosorosea strain successfully knocked down the host target gene by infecting the nymphs and enhanced the whiteflies mortality. The present study will give insight to new application of RNAi technology for more effective biocontrol of this pests.Electronic supplementary materialThe online version of this article (doi:10.1186/s12896-015-0170-8) contains supplementary material, which is available to authorized users.

RNA Interference in Insect Vectors for Plant Viruses

“…Several previous studies have developed dsRNA delivery methods for introducing dsRNA into the insect hemocoel using microinjection with varying concentrations [34,35,36,37,38]. Other methods included feeding with dsRNA through artificial diet/oral delivery [39,40,41]; feeding with bacteria that expresses dsRNA [42], soaking in dsRNA [43]; nano-particle-mediated RNAi [44] and fungi expressing the specific dsRNA [45]. These methods were adapted for studying RNAi mechanisms in insects for research purposes, but none could be suggested as strategy for pest control under field conditions.…”

“…Recently, it was demonstrated that expressing dsRNA of whitefly in the entomapthogenic fungus Isaria fumosorosea , successfully silenced the insect Toll-like receptor 7 ( TLR7 ) gene by infecting nymphs and increased the mortality rate [45]. …”

Potential of RNA interference in the study and management of the whitefly, Bemisia tabaci

“…Efforts have been made to explore the utility of RNAi by delivering dsRNA through an entomopathogenic fungus, Isaria fumosorosea (Chen et al, ). This fungus enters the insect body through the cuticle and is then able to invade the insect hemocoel.…”

Implementing the sterile insect technique with RNA interference – a review

“…eRNAi has been demonstrated to successfully achieve gene silencing in adults following ingestion of: (1) dsRNA‐expressing transgenic plants (Coleman et al., ; Tzin et al., ; Malik et al., ), (2) dsRNA‐expressing transgenic bacteria (Li et al., ; Taracena et al., ; Whitten et al., ), (3) dsRNA dissolved in solution (Coy et al., ; Ratzka et al., ; Shim et al., ), and (4) naked dsRNA overlaid on diet (Yi et al., ; Zheng et al., ). In addition, topical application to adults of dsRNA (Pridgeon et al., ; Killiny et al., ; Amiri et al., ) and infection with transgenic fungi (Chen et al., ) are reported. All methods have the potential for use in SIT development.…”