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

Caccia, Silvia; Astarita, Federica; Barra, Enrica; Lelio, Ilaria Di; Varricchio, Paola; Pennacchio, Francesco

doi:10.1007/s10340-019-01140-6

Cited by 41 publications

(44 citation statements)

References 59 publications

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“…The dsRNA concentration was determined spectrophotometrically and the quality checked on a 1% agarose gel. A GFP dsRNA, exploited in control experiments, was similarly produced starting from the cloning vector pcDNA 3.1/CT-GFP TOPO (Thermo Fisher Scientific), which was used as template for a PCR reaction, performed as described elsewhere [ 63 ].…”

Section: Methodsmentioning

confidence: 99%

A salivary chitinase of Varroa destructor influences host immunity and mite’s survival

et al. 2020

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Varroa destructor is an ectoparasite of honey bees and an active disease vector, which represents one of the most severe threats for the beekeeping industry. This parasitic mite feeds on the host’s body fluids through a wound in the cuticle, which allows food uptake by the mother mite and its progeny, offering a potential route of entrance for infecting microorganisms. Mite feeding is associated with saliva injection, whose role is still largely unknown. Here we try to fill this gap by identifying putative host regulation factors present in the saliva of V. destructor and performing a functional analysis for one of them, a chitinase (Vd-CHIsal) phylogenetically related to chitinases present in parasitic and predatory arthropods, which shows a specific and very high level of expression in the mite’s salivary glands. Vd-CHIsal is essential for effective mite feeding and survival, since it is apparently involved both in maintaining the feeding wound open and in preventing host infection by opportunistic pathogens. Our results show the important role in the modulation of mite-honey bee interactions exerted by a host regulation factor shared by different evolutionary lineages of parasitic arthropods. We predict that the functional characterization of Varroa sialome will provide new background knowledge on parasitism evolution in arthropods and the opportunity to develop new bioinspired strategies for mite control based on the disruption of their complex interactions with a living food source.

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Section: Methodsmentioning

confidence: 99%

A salivary chitinase of Varroa destructor influences host immunity and mite’s survival

et al. 2020

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“…[26][27][28][29] For example, knocking out the Sl102 gene, which is involved in the immune pathway in Spodoptera littoralis, significantly improved the effect of a Bt-based biopesticide. 30 Previous studies have confirmed that CAN regulates expression of antimicrobial peptides and immune-related genes through the Toll or IMD pathway in insects. 17,31,32 In this study, we explored the possibility of suppressing HaCAN through a bioassay involving insect cells and second-and fifthinstar larvae, which would enhance the insecticidal activity of Cry2Ab to the larvae of H. armigera.…”

Section: Introductionmentioning

confidence: 95%

“…The feeding of Bt toxins also activates a series of immune signal pathways 26–29 . For example, knocking out the Sl102 gene, which is involved in the immune pathway in Spodoptera littoralis , significantly improved the effect of a Bt‐based biopesticide 30 . Previous studies have confirmed that CAN regulates expression of antimicrobial peptides and immune‐related genes through the Toll or IMD pathway in insects 17,31,32 …”

Section: Introductionmentioning

confidence: 99%

Suppressing calcineurin activity increases the toxicity of Cry2Ab to Helicoverpa armigera

Wei

Yang

Zhou

et al. 2021

Pest Management Science

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BACKGROUND Extensive planting of transgenetic Bacillus thuringiensis crops has driven the evolution of pest resistance to Cry1Ac. Adjustment of cropping structures has promoted further outbreak of Helicoverpa armigera in China. To control this pest, a combination of pyramiding RNA interference (RNAi) and Cry2Ab is considered a promising strategy for countering cross‐resistance and enhancing the toxicity of Cry2Ab to cotton bollworm. We explored the possibility of using calcineurin (CAN) as a target RNAi gene, because it is involved in cotton bollworm responses to the toxicity of Cry2Ab. RESULTS Cry2Ab treatment led to a significant increase in HaCAN mRNA level and HaCAN activity. Suppression of HaCAN activity due to RNAi‐mediated knockdown of HaCAN increased the susceptibility of midgut cells to Cry2Ab. The increase in HaCAN activity shown by heterologous expression of HaCAN reduced the cytotoxicity of Cry2Ab to Sf9 cells. Moreover, ingestion of HaCAN‐specific inhibitor FK506 increased the toxicity of Cry2Ab in larvae. Interestingly, HaCAN does not function as a Cry2Ab direct binding protein that participates in Cry2Ab toxicity. CONCLUSIONS The results in this study provide evidence that suppression of HaCAN not only affected the development of the cotton bollworm, but also enhanced the toxicity of Cry2Ab to the pest. HaCAN is therefore an important candidate gene in cotton bollworm that can be targeted for pest control when the pest infests RNAi+Cry2Ab crops. Meanwhile, the mechanism of action of HaCAN in Cry2Ab toxicity suggested that protein dephosphorylation was involved. © 2020 Society of Chemical Industry

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“…Therefore, the ideal “pyramid” strategy should simultaneously target different action pathways with synergetic effects on each other. The knockout of an immune gene Sl 102 in Spodoptera littoralis was recently verified to improve the effect of spray applications of the Bt-based biopesticide (Xentari TM ) ( Caccia et al, 2020 ). In fact, feeding with Bt toxins themselves activates a series of immune signal pathways ( Chai et al, 2008 ; Xia et al, 2016 ; Portugal et al, 2017 ).…”

Section: Introductionmentioning

confidence: 99%

Suppression of Calcineurin Enhances the Toxicity of Cry1Ac to Helicoverpa armigera

et al. 2021

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Insect resistance to Bacillus thuringiensis (Bt) insecticidal proteins has rapidly evolved with the expansion of the planting area of transgenic Bt crops. Pyramiding RNA interference (RNAi) and Bt in crops is urgently needed to counter the rapid increase in pest resistance. The ideal “pyramid” strategy simultaneously targets different action pathways that exert synergetic effects on each other. Here, we identified a dephosphatase, namely, Helicoverpa armigera calcineurin (HaCAN), which might enhance the insecticidal activity of Cry1Ac against Helicoverpa armigera by regulating immune gene expression via dephosphatase activity, but not by acting as a receptor. Notably, blocking enzyme activity or knocking down endogenous HaCAN significantly promoted the enhancement in Cry1Ac toxicity to insect larvae and cells. Correspondingly, the increase in HaCAN activity reduced the cytotoxicity of Cry1Ac as shown by the heterologous expression of HaCAN. Our results provide a probable that HaCAN is an important candidate gene for pyramiding RNAi and Cry1Ac crops to control cotton bollworm.

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

Cited by 41 publications

References 59 publications

A salivary chitinase of Varroa destructor influences host immunity and mite’s survival

A salivary chitinase of Varroa destructor influences host immunity and mite’s survival

Suppressing calcineurin activity increases the toxicity of Cry2Ab to Helicoverpa armigera

Suppression of Calcineurin Enhances the Toxicity of Cry1Ac to Helicoverpa armigera

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