Optimization of recombinant bacteria expressing dsRNA to enhance insecticidal activity against a lepidopteran insect, Spodoptera exigua

Vatanparast, Mohammad; Kim, Yonggyun

doi:10.1371/journal.pone.0183054

Cited by 51 publications

(48 citation statements)

References 42 publications

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“…Sonication treatment might impair the bacterial membrane through physical damage that results in leaks, through which the dsRNA in bacterial cells might be easily passed. Enhanced insecticidal activity by ultra‐sonication pretreatment has been observed in the application of dsRNA‐expressing bacteria to S. exigua . Thus, a dsRNA delivery system using recombinant bacteria pretreated with sonication can improve the insecticidal activity of dsRNA against lepidopteran insect pests.…”

Section: Discussionmentioning

confidence: 99%

“…Enhanced insecticidal activity by ultra-sonication pretreatment has been observed in the application of dsRNA-expressing bacteria to S. exigua. 34,38 Thus, a dsRNA delivery system using recombinant bacteria pretreated with sonication can improve the insecticidal activity of dsRNA against lepidopteran insect pests. This is the first study to report that dsRNA can be applied to control M.…”

Section: Discussionmentioning

confidence: 99%

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Alteration of insulin signaling to control insect pest by using transformed bacteria expressing dsRNA

Baki

Jung

Kim

2019

Pest Management Science

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BACKGROUND Insulin/insulin‐like growth factor signaling (IIS) is known to mediate larval growth and adult reproduction in the legume pod borer, Maruca vitrata (Lepidoptera: Crambidae). Four IIS components (InR, FOXO, Akt, and TOR) play crucial roles in the IIS pathway. RESULTS RNA interference (RNAi) against any of these four IIS component genes was effective in suppressing each target mRNA level by either hemocoelic injection or oral administration using gene‐specific double‐stranded RNAs (dsRNAs). These RNAi treatments interfered with larval growth, leading to small pupae or significant larval mortality. For massive production of dsRNA, transformed bacteria expressing dsRNAs of these four IIS components were prepared with L4440 expression vector and HT115 strain of Escherichia coli. The transformed bacteria killed the larvae in a dose‐dependent manner by feeding administration. An ultra‐sonication pretreatment was performed to impair bacterial membrane and increase dsRNA release from the bacteria in insect intestine. This pretreatment increased the insecticidal activity of these recombinant bacteria. To further increase dsRNA toxicity, its mixture with Bacillus thuringiensis (Bt) was prepared and showed significant increase of Bt insecticidal activity in the laboratory. The bacterial mixture also showed a high control efficacy (83.3%) in an adzuki bean (Vigna angularis) field infested by M. vitrata. Furthermore, such a dsRNA effect was specific for M. vitrata, but not for non‐target insects. CONCLUSION The bacteria expressing dsRNA specific to IIS components can be used to develop dsRNA insecticide. © 2019 Society of Chemical Industry

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Alteration of insulin signaling to control insect pest by using transformed bacteria expressing dsRNA

Baki

Jung

Kim

2019

Pest Management Science

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“…On the other hand, a study performed with S. exigua used both live and heat‐killed transgenic E. coli cells expressing β1 integrin dsRNA. There was no difference in mortality rate (30–35%) with treatment using either live or heat‐killed bacteria . Thus, the susceptibility to RNAi effects with either live or killed bacteria might be species dependent.…”

Section: Strategies For Oral Administration Of Dsrna In Insects and Imentioning

confidence: 91%

“…There was no difference in mortality rate (30-35%) with treatment using either live or heat-killed bacteria. 105 Thus, the susceptibility to RNAi effects with either live or killed bacteria might be species dependent. A factor to consider is that the use of live bacteria as a sprayable form on plants might raise some safety concerns and, most likely, regulatory agencies will be hesitant to approve this method.…”

Section: Transformed Microorganisms and Virusesmentioning

confidence: 99%

Prospects, challenges and current status of RNAi through insect feeding

Kunte

McGraw

Bell

et al. 2019

Pest Management Science

125

134

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RNA interference is a phenomenon in which the introduction of double‐stranded RNA (dsRNA) into cells triggers the degradation of the complementary messenger RNA in a sequence‐specific manner. Suppressing expression of vital genes could lead to insect death, therefore this technology has been considered as a potential strategy for insect pest control. There are three main routes of dsRNA administration into insects: (i) injections to the hemolymph, (ii) topical, and (iii) feeding. In this review, we focus on dsRNA administration through feeding. We summarize novel strategies that have been developed to improve the efficacy of this method, such as the use of nano‐based formulations, engineered microorganisms, and transgenic plants. We also expose the hurdles that have to be overcome in order to use this technique as a reliable pest management method. © 2019 Society of Chemical Industry

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“…Tian et al (2009) first reported the efficacy of bacterially expressed dsRNA in the induction of systemic RNAi in insects, in particular in the lepidopteran pest Spodoptera exigua. Several other studies have clearly shown that bacterial delivery (1) is cost-effective, (2) protects dsRNA molecules against degradation and (3) allows the development of new plant protection products/tools (Kim et al 2015;Lim et al 2016;Zhu et al 2016;Ganbaatar et al 2017;Israni and Rajam 2017;Vatanparast and Kim 2017;Wang et al 2018).…”

Section: Introductionmentioning

confidence: 99%

Enhancement of Bacillus thuringiensis toxicity by feeding Spodoptera littoralis larvae with bacteria expressing immune suppressive dsRNA

Caccia¹,

Astarita²,

Barra³

et al. 2019

J Pest Sci

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RNAi interference (RNAi) for insect pest control is often used to silence genes controlling vital functions, thus generating lethal phenotypes. Here, we propose a novel approach, based on the knockout of an immune gene by dsRNA-expressing bacteria as a strategy to enhance the impact of spray applications of the entomopathogen Bacillus thuringiensis (Bt). The target gene, Sl 102, controls the encapsulation and nodulation responses in the noctuid moth Spodoptera littoralis (Lepidoptera, Noctuidae). To deliver Sl 102 dsRNA, we have developed a bacterial expression system, using HT115 Escherichia coli. This allows a much cheaper production of dsRNA and its protection against degradation. Transformed bacteria (dsRNA-Bac) administered through artificial diet proved to be more effective than dsRNA synthesized in vitro, both in terms of gene silencing and immunosuppression. This is a likely consequence of reduced dsRNA environmental degradation and of its protected release in the harsh conditions of the gut. The combined oral administration with artificial diet of dsRNA-Bac and of a Bt-based biopesticide (Xentari™) resulted in a remarkable enhancement of Bt killing activity, both on 4th and 5th instar larvae of S. littoralis, either when the two components were simultaneously administered or when gene silencing was obtained before Bt exposure. These results pave the way toward the development of novel Bt spray formulations containing killed dsRNA-Bac, which synergize Bt toxins by suppressing the insect immune response. This strategy will preserve the long-term efficacy of Bt-based products and can, in principle, enhance the ecological services provided by insect natural antagonists. Key message• RNAi for insect control requires the development of effective delivery strategies of dsRNA. • Bacteria expressing a dsRNA targeting an immune gene induce its silencing when ingested by larvae of the noctuid moth Spodoptera littoralis. • The resulting immunosuppression enhances the killing activity of a Bt-based biopesticide.• These immune suppressive bacteria can be used as synergistic factors to develop more effective Bt sprays, and to preserve Bt efficacy.Communicated by E. Roditakis.* S. Caccia

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Optimization of recombinant bacteria expressing dsRNA to enhance insecticidal activity against a lepidopteran insect, Spodoptera exigua

Cited by 51 publications

References 42 publications

Alteration of insulin signaling to control insect pest by using transformed bacteria expressing dsRNA

Alteration of insulin signaling to control insect pest by using transformed bacteria expressing dsRNA

Prospects, challenges and current status of RNAi through insect feeding

Enhancement of Bacillus thuringiensis toxicity by feeding Spodoptera littoralis larvae with bacteria expressing immune suppressive dsRNA

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