Abstract
The oriental fruit fly Bactrocera dorsalis (Hendel) (Diptera: Tephritidae) is an important invasive pest with high reproductive capacity and invasiveness; it has shown remarkable range expansion and brings higher risk to the environment and agriculture. The insect cuticle serves as skin and skeleton, protecting insects against numerous harmful stresses. One gene named imaginal disc growth factor 4 (idgf4) which is involved in cuticle formation, plays an important role in organizing proteins in the chitin-matrix, as well as in adult molting. This gene in the poorly-described glycoside hydrolase 18 (GH 18) family was chosen to study the function of chitinases in insect defense barrier against heat and molting using quantitative real-time PCR (qRT-PCR) and RNA interference (RNAi). qRT- PCR showed that idgf4 was expressed in all nine developmental stages and was mainly expressed in the early and late pupal, as well as adult stages. Knocking down the idgf4 gene via RNAi in 3rd instar larvae led to the decreased survival of larvae under high temperatures and malformed individuals as adults. The results indicated the function of the idgf4 gene in the fruit fly’s defense barrier and development. It can provide new insights into understanding the function of one member in the GH 18 family, and may reveal a new potential gene for pest control.
Highlights
Tephritid flies attack a large variety of fruits, which can be highly priced commodities in many countries[1]
To investigate the evolutionary relationship between idgf[4] in B. dorsalis and other idgf4s, a phylogenetic analysis was performed with two different methods, the neighbor-joining and the maximum-likelihood methods
One group in Z. cucurbitae was similar to C. capitata isoform X2, and one was more similar to the Bactrocera group (Figs 2 and S1)
Summary
Tephritid flies attack a large variety of fruits, which can be highly priced commodities in many countries[1]. Considering its role in high levels of economic loss and an expanding wider distribution, several methods, including destruction of the fallen and infested fruits, cold and heat treatments, bait sprays, biological control methods, sterile insect techniques (SIT) and usage of insecticides have been developed in the last few decades for controlling this notorious pest[8,9,10,11,12,13,14,15]. Among all these methods, insecticides still represent the most effective strategy[15,16]. The cold tolerance and low temperature activity of winter-acclimated flies is related to increased cuticle melanization[43]
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