Abstract: 【Aim】 Based on the transcriptome data of the whitefly, Bemisia tabaci, this study aims to systematically analyze the expression profiles of genes encoding detoxification enzymes in thiamethoxam resistant strain, and to focus on discussing the biological significance of developmental stage specific differential expression of these genes. 【Methods】 Thiamethoxam resistant (TH-R) and susceptible (TH-S) strains of B. tabaci were maintained in a greenhouse, and individuals at three developmental stages (egg, the 4th instar nymph and 1 day-old unmated female adult) were collected from the TH-R and TH-S strains. The array design was based on 8 394 ESTs from transcriptome of B. tabaci with putative association with insecticide resistance. By using a custom made microarray, the gene expression in eggs, nymphs and female adults of the TH-R strain of B. tabaci was compared. Nine ESTs were randomly selected for quantitative real-time PCR (qRT-PCR) analysis to validate the microarray response between the TH-R and TH-S strains at three different developmental stages. 【Results】 In the TH-R strain, a total of 3 424 ESTs were differentially expressed between the egg and 4th instar nymphal stages. Among them, 489 ESTs encode detoxification enzymes (carboxylesterase, glutathione S-transferases, cytochrome P450 monooxygenases). Fourteen ESTs (10 ESTs encoding P450s, and 4 ESTs encoding GSTs) were overexpressed in the 4th instar nymphal stage. There were 1 273 ESTs which were differentially expressed between the 4th instar nymphal and female adult stages. Among them, 193 genes encoding detoxification enzymes and nine ESTs encoding P450s showed higher expression level (10-fold) in the female adult stage rather than the 4th instar nymphal stage. The qRT-PCR results revealed that nine ESTs were up-regulated in the TH-R strain at three developmental stages compared to those in the TH-S strain. The EST p_06027 and the EST p_06013 encoding P450s were overexpressed in egg and the 4th instar nymphal stage of the TH-R strain. The ESTs p_05885, p_07806 and the EST p_00988 encoding P450s were highly overexpressed in the 4th instar nymphal stage of the TH-R strain. The ESTs p_05885, p_07806 and the EST p_00988 encoding P450s were highly overexpressed in the 4th instar nymphal stage of the TH-R strain. The ESTs p_05916 and p_00478 had low expression levels in the egg and 4th instar nymphal stages but overexpressed in the female adult stage of the TH-R strain. The ESTs p_00059 and p_00428 were significantly up-regulated in the female adult stage but had low expression level in the other two immature stages of TH-R strain, and the EST p_00059 encoding CYP4C1 with the highest expression level (~15.15-fold) was seen in the female adult stage. 【Conclusion】 The results suggest that the overexpression of CYP4C1 and CYP6B may underlie the resistance to thiamethoxam in B. tabaci. According to the microarray data analyzed, the detoxification enzyme genes are differentially expressed in different developmental stages of B. tabaci, which may be associated with the distribution and effective utilization of energy under the stress of insecticides and also an adaptive mechanism under the environmental selection pressures.

Key words: Bemisia tabaci; resistance, thiamethoxam, detoxification enzyme, microarray, developmental stage specificity