This bug nymph induces RNAi-mediated silencing of the targeted

This study demonstrates that microinjection of dsRNA into kudzu
bug nymph induces RNAi-mediated silencing of the targeted transcript confirmed
by RT-PCR. The phenotypic effects of RNAi seen were signi?cant mortality and
larval growth inhibition. The knockdown of kbcat transcript suggest that RNAi a
specie-specific, is a useful tool for silencing antioxidant enzymes specific
genes. Insect body utilizes antioxidant enzymes such as superoxide dismutase,
catalase and glutathione peroxidase as their major defense mechanism (Li et
al., 2005). In this study, we cloned kudzu bug catalase and further studied
their biological function, which interestingly resulted in a significant mortality
and growth inhibition.

Al-ayedh and his colleague (2016), reported that knocking down of cat gene in Rhynchophorus ferrugineus significantly
increase mortality and growth inhibition. Similarly, Diaz-Albiter et al.,
confirmed silenced catalase gene expression led to a significant mortality rate
in female Lutzomyia longipalpis. In addition, other studies have also
reported mortality after given dsRNA corresponding to catalase gene. Haiming et
al., (2013), reported that Spodoptera litura survival
rate were decreased when injected with catalase dsRNA. Similarly, Gong et al.,
(2011) observed 73% mortality of Plutella
xylostella when treated with siRNA of Rieskiron–sulfur protein gene. Treatment
of acetylcholinesterase siRNA also led to larval mortality and growth
inhibition of Helicoverpa armigera. All these result is an indication of the
ef?ciency of RNAi in different insects species with catalase gene. In this
study, the survival rate of the kudzu bug reduces after 3 days of post
injection. Therefore, this results confirm that catalase gene plays a major
role in different species and required for normal growth and development of the
insect.

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RNAi-mediated
gene silencing in kudzu bug outline an important tool for investigating
alternative pest management approaches. Since its discovery, RNAi has played an
essential role in functional genetics studies. It has been used in many model
systems including Drosophila melanogaster
(Roignant et al., 2003; Bischoff et al., 2006; Miller et al., 2008), Tribolium castaneum (Tomoyasu and
Denell, 2004; Fujita et al., 2006; Arakane et al., 2008; Konopova and Jindra,
2008; Minakuchi et al., 2009; Parthasarathy and Palli, 2009) and Bombyx mori (Quan et al., 2002; Ohnishi
et al., 2006; Hossain et al., 2008) to study loss-of-function phenotypes for a
wide-array of genes. Such functional genomic studies provide researchers with a
greater understanding of the genes involved in biological phenomena like physiology,
embryology, reproduction and behavior in both model and non-model insects
(Bellés, 2010). The reason researchers are fascinated by the potential use of
RNAi for insect control, is the fact that it is species-specific (Baum et al.,
2007; Whyard et al., 2009; Bellés, 2010; Terenius et. al., 2011), can be
delivered by a variety of methods (Baum et al., 2007; Scott et al., 2013;
Terenius et al., 2011), and could possibly serve as an eco-friendly pest
management tool that could be modified for use in a wide range of insect pests
(Borovsky, 2005; Gordon and Waterhouse, 2007; Price and Gatehouse, 2008).
Unlike conventional pesticides, RNAi appears to have minimal off-target effects
(Birmingham et. al. 2006).

Given the specificity of RNAi technology, its
use in transgenic plants expressing dsRNA to suppress vital genes in specific
insect pests upon ingestion offers a new approach to crop pests control (Baum
et al. 2007; Mao et al. 2007). We propose appropriate target genes must be
identified for each new species to be controlled by this strategy ouline in
this study. One way to identify potential target genes is through homology to
ones used in previous studies.   An added
advantage of using highly conserved genes is that they can be easily recognized
in database searches. Blast analysis of NCBI and other genomic and
transcriptomic databases can reveal potential target genes for a wide number of
species, however, if the target species lacks genomic and transcriptomic data,
these sequences can be easily obtained by extracting RNA and performing
RNA-Seq. This type of next generation sequencing is a rapid method of obtaining
a wealth of genetic data and allows identification of novel transcripts;
especially in non-model insects that lack a sequenced genome (Wang et. al.
2011). Homologous genes can be quickly identified based on identity to known
targets (e.g. V-ATPase), and offers an easy way to select candidate genes for
RNAi analysis.

In conclusion, before this techniques could
potential becoming a successful approach for management of kudzu bug being a
relatively new pest, several issues need to be addressed before this technology
can be used in the field. To further our understanding of the systemic RNAi in
kudzu bug, RNAi pathways in this species needs to be identified and their roles
should be studied. Moreover, extensive studies are needed to completely
understand which method one must consider relatively to the end goal (e.g. pest
control), to enables delivery of dsRNAs in a high-throughput manner. In addition,
RNAi delivered by feeding is of particular interest for insect control in
agriculture as they can act as a species-specific insecticide (Baum et al.,
2007). Despite various setbacks associated with this technology, perhaps in the
future, RNAi will be a widely-accepted tool for used in integrated pest
management.