Scorpion neurotoxin AaIT-expressing Beauveria bassiana enhances the virulence against Aedes albopictus mosquitoes

AMB Express, Jun 2017

To improve the insecticidal efficacy of this entomopathogen Beauveria bassiana, the fungus was genetically modified to express an insect-specific scorpion neurotoxin AaIT. The virulence of the recombinant B. bassiana strain (Bb-AaIT) against Aedes albopictus adults (which occurs via penetration through the cuticle during spore germination or by conidia ingestion), and the larvae (by conidia ingestion) was measured with bioassays. The median lethal concentration (LC50) of Bb-AaIT against A. albopictus larvae was 313.3-fold lower on day 4 and 11.3-fold lower on day 10 than that of the wild type (WT). Through conidia feeding or body contact, Bb-AaIT killed 50% of adult female mosquitoes at 3.9- or 1.9-fold reduced concentrations on day 4 and at 2.1- or 2.4-fold reduced concentrations on day 10. Compared with the results for the WT, the median lethal time (LT50) of Bb-AaIT was reduced by 28.6% at 1 × 107 conidia ml−1 and 34.3% at 1 × 106 conidia ml−1 in the larvae bioassay by conidia ingestion, while it decreased 32.3% at 1 × 107 conidia ml−1 by conidia ingestion and 24.2% at 1 × 108 conidia ml−1 by penetrating through the cuticle in the adult bioassay. All the differences were significant. Our findings indicated that Bb-AaIT had higher virulence and faster action than the WT in killing the larval and adult mosquitoes, and therefore, it is valuable for development as a commercial mosquito pesticide.

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Scorpion neurotoxin AaIT-expressing Beauveria bassiana enhances the virulence against Aedes albopictus mosquitoes

Deng et al. AMB Expr Scorpion neurotoxin AaIT-expressing Beauveria bassiana enhances the virulence against Aedes albopictus mosquitoes Sheng‑Qun Deng 0 Qun‑Di Cai 0 Ming‑Zhi Deng 0 Qiang Huang 0 HongJ‑uan Peng 0 0 Department of Pathogen Biology, Guangdong Provincial Key Laboratory of Tropical Disease Research, and Key Laboratory of Prevention and Control for Emerging Infectious Diseases of Guangdong Higher Institutes, School of Public Health, Southern Medical University , Guangzhou 510515, Guangdong Province , China To improve the insecticidal efficacy of this entomopathogen Beauveria bassiana, the fungus was genetically modified to express an insect‑ specific scorpion neurotoxin AaIT. The virulence of the recombinant B. bassiana strain (Bb‑ AaIT) against Aedes albopictus adults (which occurs via penetration through the cuticle during spore germination or by conidia ingestion), and the larvae (by conidia ingestion) was measured with bioassays. The median lethal concentration (LC50) of Bb‑ AaIT against A. albopictus larvae was 313.3‑ fold lower on day 4 and 11.3‑ fold lower on day 10 than that of the wild type (WT). Through conidia feeding or body contact, Bb‑ AaIT killed 50% of adult female mosquitoes at 3.9‑ or 1.9‑ fold reduced concentrations on day 4 and at 2.1‑ or 2.4‑ fold reduced concentrations on day 10. Compared with the results for the WT, the median lethal time (LT50) of Bb‑ AaIT was reduced by 28.6% at 1 × 107 conidia ml−1 and 34.3% at 1 × 106 conidia ml−1 in the larvae bioassay by conidia ingestion, while it decreased 32.3% at 1 × 107 conidia ml−1 by conidia ingestion and 24.2% at 1 × 108 conidia ml−1 by penetrating through the cuticle in the adult bioassay. All the differences were significant. Our findings indicated that Bb‑ AaIT had higher virulence and faster action than the WT in killing the larval and adult mosquitoes, and therefore, it is valuable for development as a commercial mosquito pesticide. Beauveria bassiana; Aedes albopictus; Scorpion neurotoxin; Virulence - Mosquito-borne diseases create a significant burden every year. For example, malaria caused 438,000 deaths in 2015, and the dengue incidence has risen 30-fold in the past 30 years around the world (WHO 2016). The Asian tiger mosquito Aedes albopictus transmits many viral infections, including the yellow fever, dengue and Chikungunya (Hochedez et al. 2006), as well as several filarial nematodes such as Dirofilaria immitis (Cancrini et  al. 2003). Aedes albopictus is capable of hosting the Zika virus and is considered a potential vector for Zika transmission among humans (Paupy et  al. 2009; Wong et  al. 2013). Because more than half of the world’s population lives in areas where this mosquito species is present, sustained mosquito control efforts are important to prevent outbreaks from these diseases (Kamareddine et al. 2013). Chemical insecticides have been used intensively as the primary strategy for controlling mosquito populations. However, this strong dependence on insecticides for mosquito control around the world and the use of these chemicals in agriculture have led to environmental pollution and toxic hazards to humans and other non-target organisms (Al-Sarar 2010). The physiological resistance of important mosquito vectors has been widely reported in recent years (Agra-Neto et  al. 2014; Bilal et  al. 2012; Labbe et al. 2007; Lima et al. 2011; Stenhouse et al. 2013; Zou et al. 2006). Entomopathogenic fungi, such as Beauveria bassiana and Metarhizium anisopliae, have tremendous potential for use as pest biological control agents, particularly as alternatives to chemical pesticides (Lacey et  al. 2001; Lomer et  al. 2001). B. bassiana is an environmentally © The Author(s) 2017. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. friendly fungus (Roberts and St Leger 2004; Thomas and Read 2007; Wang et al. 2004), and it is widely distributed and has a broad host range towards diverse insect species in nature (Reynolds and Samuels 1996). Many B. bassiana strains have been selected for vector and crop pest control, including house and fruit flies (Dimbi et al. 2003; Lecuona et  al. 2005), mosquitoes (Bukhari et  al. 2011; Clark et  al. 1968; Garcia-Munguia et  al. 2011), ticks (Kirkland et  al. 2004), locusts, grasshoppers, and termites (Kassa et al. 2004; Mburu et al. 2009). However, the slow killing speed associated with these mycoinsecticides is a major deterrent to their commercial use and large-scale application, and thus they are unable to compete with faster-acting and cheaper chemical insecticides (Amsellem et al. 2002; St Leger et al. 1996). AaIT is a single-chain ne (...truncated)


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Sheng-Qun Deng, Qun-Di Cai, Ming-Zhi Deng, Qiang Huang, Hong-Juan Peng. Scorpion neurotoxin AaIT-expressing Beauveria bassiana enhances the virulence against Aedes albopictus mosquitoes, AMB Express, 2017, pp. 121, Volume 7, Issue 1, DOI: 10.1186/s13568-017-0422-1