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
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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
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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)