This study demonstrates that microinjection of dsRNA into kudzubug nymph induces RNAi-mediated silencing of the targeted transcript confirmedby RT-PCR. The phenotypic effects of RNAi seen were signi?cant mortality andlarval growth inhibition. The knockdown of kbcat transcript suggest that RNAi aspecie-specific, is a useful tool for silencing antioxidant enzymes specificgenes. Insect body utilizes antioxidant enzymes such as superoxide dismutase,catalase and glutathione peroxidase as their major defense mechanism (Li etal., 2005). In this study, we cloned kudzu bug catalase and further studiedtheir biological function, which interestingly resulted in a significant mortalityand growth inhibition.Al-ayedh and his colleague (2016), reported that knocking down of cat gene in Rhynchophorus ferrugineus significantlyincrease mortality and growth inhibition.
Similarly, Diaz-Albiter et al.,confirmed silenced catalase gene expression led to a significant mortality ratein female Lutzomyia longipalpis. In addition, other studies have alsoreported mortality after given dsRNA corresponding to catalase gene. Haiming etal., (2013), reported that Spodoptera litura survivalrate were decreased when injected with catalase dsRNA.
Similarly, Gong et al.,(2011) observed 73% mortality of Plutellaxylostella when treated with siRNA of Rieskiron–sulfur protein gene. Treatmentof acetylcholinesterase siRNA also led to larval mortality and growthinhibition of Helicoverpa armigera. All these result is an indication of theef?ciency of RNAi in different insects species with catalase gene. In thisstudy, the survival rate of the kudzu bug reduces after 3 days of postinjection. Therefore, this results confirm that catalase gene plays a majorrole in different species and required for normal growth and development of theinsect.RNAi-mediatedgene silencing in kudzu bug outline an important tool for investigatingalternative pest management approaches.
Since its discovery, RNAi has played anessential role in functional genetics studies. It has been used in many modelsystems including Drosophila melanogaster(Roignant et al., 2003; Bischoff et al., 2006; Miller et al., 2008), Tribolium castaneum (Tomoyasu andDenell, 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; Ohnishiet al., 2006; Hossain et al., 2008) to study loss-of-function phenotypes for awide-array of genes. Such functional genomic studies provide researchers with agreater 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 ofRNAi 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 bedelivered 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 pestmanagement 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, itsuse in transgenic plants expressing dsRNA to suppress vital genes in specificinsect pests upon ingestion offers a new approach to crop pests control (Baumet al.
2007; Mao et al. 2007). We propose appropriate target genes must beidentified for each new species to be controlled by this strategy ouline inthis study. One way to identify potential target genes is through homology toones used in previous studies. An addedadvantage of using highly conserved genes is that they can be easily recognizedin database searches. Blast analysis of NCBI and other genomic andtranscriptomic databases can reveal potential target genes for a wide number ofspecies, however, if the target species lacks genomic and transcriptomic data,these sequences can be easily obtained by extracting RNA and performingRNA-Seq.
This type of next generation sequencing is a rapid method of obtaininga 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 knowntargets (e.
g. V-ATPase), and offers an easy way to select candidate genes forRNAi analysis.In conclusion, before this techniques couldpotential becoming a successful approach for management of kudzu bug being arelatively new pest, several issues need to be addressed before this technologycan be used in the field. To further our understanding of the systemic RNAi inkudzu bug, RNAi pathways in this species needs to be identified and their rolesshould be studied. Moreover, extensive studies are needed to completelyunderstand which method one must consider relatively to the end goal (e.
g. pestcontrol), to enables delivery of dsRNAs in a high-throughput manner. In addition,RNAi delivered by feeding is of particular interest for insect control inagriculture as they can act as a species-specific insecticide (Baum et al.,2007).
Despite various setbacks associated with this technology, perhaps in thefuture, RNAi will be a widely-accepted tool for used in integrated pestmanagement.
