Abstract
Bemisia tabaci has developed a high level of resistance to thiamethoxam, a second generation neonicotinoid insecticide that has been widely used to control this pest. In this study, we investigated whether hydroxyacid-oxoacid transhydrogenase (HOT) is involved in resistance to the neonicotinoid insecticide thiamethoxam in the whitefly. We cloned the full-length gene that encodes HOT in B. tabaci. Its cDNA contains a 1428-bp open reading frame encoding 475 amino acid residues. Then we evaluated the mRNA expression level of HOT in different developmental stages, and found HOT expression was significantly greater in thiamethoxam resistance adults than in thiamethoxam susceptible adults. Subsequently, seven field populations of B. tabaci adults were sampled, the expression of mRNA level of HOT significant positive correlated with thiamethoxam resistance level. At last, we used a modified gene silencing system to knock-down HOT expression in B. tabaci adults. The results showed that the HOT mRNA levels decreased by 57% and thiamethoxam resistance decreased significantly after 2 days of feeding on a diet containing HOT dsRNA. The results indicated that down-regulation of HOT expression decreases thiamethoxam resistance in B. tabaci adults.
Highlights
DHQ_Fe-ADH superfamily resistance in B. tabaci[10]
The results showed that the expression of a suite of phase I and phase II detoxification enzymes, including cytochrome P450s, UDP-glucuronosyltrans-ferases, glutathione S-transferases (GST), and several ABC transporters was substantially elevated in THR12
The results showed that thiamethoxam mortality remained low when adults were fed with GFP dsRNA but increased significantly when adults were fed with hydroxyacid-oxoacid transhydrogenase (HOT) dsRNA at three concentrations of this insecticide (250, 500 and 1000 mg/L) (Fig. 8B)
Summary
DHQ_Fe-ADH superfamily resistance in B. tabaci[10]. CYP6CM1 and another P450 gene, CYP4C64, have been associated with imidacloprid resistance in field populations of B. tabaci in China[11]. “Omics” analyses and a microarray have been used to examine differences between a thiamethoxam-resistant strain (THR) and a -susceptible strain (THS) of B. tabaci at both transcriptional and translational levels. Based on the results of the differential screening, 298 and 209 clones were picked and sequenced, respectively, from the forward and reverse cDNA libraries, representing genes that were up- and down-regulated in THR relative to THS. One encoding a hydroxyacid-oxoacid transhydrogenase (HOT) EST (previously named as NAD-dependent methanol dehydrogenase-like EST) was substantially over-expressed (~12-fold) in the THR strain[13]. We cloned the full-length HOT gene in B. tabaci, evaluated its mRNA expression level in different developmental stages, determined the resistance level of thiamethoxam in seven field population, and evaluated the relationship between resistance rate and the mRNA level expression of HOT. We report that down-regulation of HOT decreases thiamethoxam resistance in B. tabaci adults
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