Gene Expression Profiling in the Thiamethoxam Resistant and Susceptible B-biotype Sweetpotato Whitefly,Bemisia tabaci

Abstract

Thiamethoxam has been used as a major insecticide to control the B-biotype sweetpotato whitefly, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae). Due to its excessive use, a high level of resistance to thiamethoxam has developed worldwide over the past several years. To better understand the molecular mechanisms underlying this resistance in B. tabaci, gene profiles between the thiamethoxam-resistant and thiamethoxam-susceptible strains were investigated using the suppression subtractive hybridization (SSH) library approach. A total of 72 and 52 upand down-regulated genes were obtained from the forward and reverse SSH libraries, respectively. These expressed sequence tags (ESTs) belong to several functional categories based on their gene ontology annotation. Some categories such as cell communication, response to abiotic stimulus, lipid particle, and nuclear envelope were identified only in the forward library of thiamethoxam-resistant strains. In contrast, categories such as behavior, cell proliferation, nutrient reservoir activity, sequence-specific DNA binding transcription factor activity, and signal transducer activity were identified solely in the reverse library.To study the validity of the SSH method, 16 differentially expressed genes from both forward and reverse SSH libraries were selected randomly for further analyses using quantitative realtime PCR (qRT-PCR). The qRT-PCR results were fairly consistent with the SSH results; however, only 50% of the genes showed significantly different expression profiles between the thiamethoxam-resistant and thiamethoxam-susceptible whiteflies. Among these genes, a putative NAD-dependent methanol dehydrogenase was substantially over-expressed in the thiamethoxamresistant adults compared to their susceptible counterparts. The distributed profiles show that it was highly expressed during the egg stage, and was most abundant in the abdomen of adult females.

RNA interference-mediated knockdown of the hydroxyacid-oxoacid transhydrogenase gene decreases thiamethoxam resistance in adults of the whitefly Bemisia tabaci

“…With whitefly development, HOT expression continued to drop to very low levels in THS adults but increased to high levels in THR adults, a finding which is in accord with the results obtained by Xie et al 13,. who used the suppression subtractive hybridization cDNA library approach.…”

“…Only a few genes, e.g., cytochrome P450s and GST and ABC transporters, have been associated with thiamethoxam resistance1617. In the current study, which extends a previous study13, we cloned the full-length cDNA of HOT in B. tabaci and aligned the sequence with those of other HOT genes; the results demonstrated that the B. tabaci HOT is a classic HOT gene. The relative expression of HOT in different development stages was evaluated by qRT-PCR.…”

“…capitata ) for more than 15 years without exposure to any insecticides. The THR strain was selected from the THS strain and exhibited an approximately 66-fold increase in thiamethoxam resistance relative to that of the THS strain13. A thiamethoxam-susceptible strain of B. tabaci Q (strain THQS, LC 50  = 42 mg/L) was collected from Zhejiang province in 2011 and has been maintained in the glasshouse on pepper (zhosngjiao #4, Capsicum annuuml ) for more than 3 years without exposure to insecticides.…”

“…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. Among the genes, 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 strain13. HOT catalyzes the cofactor-independent conversion of γ-hydroxybutyrate (GHB) to succinic semialdehyde (SSA) with coupled converting it to conversion of 2-oxoglutarate to D-2-hydroxyglutaric acid.…”

Transcriptomic and Proteomic Responses of Sweetpotato Whitefly, Bemisia tabaci, to Thiamethoxam

“…In addition, B. tabaci resistance to neonicotinoids, especially to thiamethoxam, has been associated with elevated activities of detoxification enzymes [25], [26]. Most recently, the molecular basis of thiamethoxam resistance in B. tabaci was investigated using the suppression subtractive hybridization (SSH) cDNA library approach [27]. 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 up- and down-regulated genes between the thiamethoxam-resistant and -susceptible B. tabaci .…”