Bemisia tabaci (Gennadius) Q biotype (BTQ) has spread to many tropical and subtropical regions over the past several decades. This may reflect an advantage biotype Q has over closely related forms in having greater thermal and/or insecticide resistance, although the effects of higher temperatures on insecticide tolerance of BTQ has, to date, been largely ignored. In this study, the effects of elevated temperatures on BTQ's tolerance to the insecticide thiamethoxam were investigated. The effect on the activities of detoxifying enzymes [carboxylesterase (CarE), glutathione S-transferase (GST), and cytochrome P450 monooxygenase (P450)] and expression profiling of eleven genes of detoxifying enzymes were also determined. In addition, RNA interference (RNAi) and bioassay methods were used to further identify the function of CYP6CM1 in tolerance to thiamethoxam following exposure to higher temperatures. The results showed that elevated temperatures were responsible for causing different outcomes in the tolerance of BTQ to thiamethoxam: Temperatures of 35 °C or higher decreased the tolerance of BTQ to thiamethoxam, while a moderately high temperature of 31 °C increased the tolerance. The high temperature influenced the tolerance of BTQ by affecting the activity of P450. Quantitative real-time PCR (qPCR) showed that CYP6CM1 was significantly up-regulated in most treatments at 31 °C, but was suppressed at 35 °C, which was closely associated with the mortality rates. Feeding on double-stranded RNA (dsRNA) of CYP6CM1 significantly reduced the mRNA levels of the target gene in the adults, and dramatically decreased tolerance to thiamethoxam induced by a temperature of 31 °C for 6 h. Our finding provides useful information to better understand the invasion mechanism of BTQ.

Background Although discrepancy in the specific traits and ecological characteristics of Bemisia tabaci between species are partially attributed to the B. tabaci-associated bacteria, the factors that affect the diversity of B. tabaci-associated bacteria are not well-understood. We used the metagenomic approach to characterize the B. tabaci-associated bacterial community because the approach is an effective tool to identify the bacteria. Methodology and Results To investigate the effects of the host plant and a virus, tomato yellow leaf curl virus (TYLCV), on the bacterial communities of B. tabaci sibling species B and Q, we analyzed the bacterial communities associated with whitefly B and Q collected from healthy cotton, healthy tomato, and TYLCV-infected tomato. The analysis used miseq-based sequencing of a variable region of the bacterial 16S rDNA gene. For the bacteria associated with B. tabaci, we found that the influence of the host plant species was greater than that of the whitefly cryptic species. With further analysis of host plants infected with the TYLCV, the virus had no significant effects on the B. tabaci-associated bacterial community. Conclusions The effects of different plant hosts and TYLCV-infection on the diversity of B. tabaci-associated bacterial communities were successfully analyzed in this study. To explain why B. tabaci sibling species with different host ranges differ in performance, the analysis of the bacterial community may be essential to the explanation.

【Background】Tomato yellow leaf curl virus( TYLCV) is one of geminiviruses,which is transmitted by the sweet potato whitefly,Bemisia tabaci. The virus can cause serious damage to economic crops,such as vegetables and tobaccoes. Previous data indicated that the virus was introduced into the southern China in 2006 and then into Shandong in 2007. The virus has been gradually spreading throughout Shandong Province since 2008. 【Method】In order to determine the dispersal time of TYLCV in Shandong Province,we surveyed 15 B. tabaci samples collected from different counties in the province from July to August in 2005 and 2006,respectively. 【Result】The results showed that the 4 B. tabaci samples in 2005 were biotype B and all of them were nonviruliferrous.The 11 B. tabaci samples in 2006 were mixed with biotypes B and Q. TYLCV was only detected within 2 of 11 samples in 2006. Molecular analysis confirmed that the virus was TYLCV. 【Conclusion and significance】The study proved for the first time that it was at least in 2006 that the TYLCV was introduced into Shandong Province. The results have important guidance not only for the prevention and control of this virus,but also have important reference value for the invasion biology of this virus.