泛素-蛋白酶体系统对烟粉虱体内番茄黄曲叶病毒的影响

Effects of ubiquitin-proteasome system on Tomato yellow leaf curl virus in whitefly Bemisia tabaci ( Hemiptera: Aleyrodidae)

【目的】泛素化修饰广泛参与细胞周期、信号传导、转录调控、免疫应答等多个方面,是细胞内一种非常重要的蛋白水平可逆修饰。但目前关于泛素-蛋白酶体系统是否参与介体昆虫传播病毒还鲜有报道。本研究旨在探索泛素-蛋白酶体系统在烟粉虱Bemisia tabaci传播番茄黄曲叶病毒(Tomato yellow leaf curl virus,TYLCV)过程中所起的作用。【方法】通过RT-qPCR分析取食感染TYLCV和不感染TYLCV番茄植物的烟粉虱成虫体内泛素和蛋白酶体亚基基因的表达,采用Western blot检测TYLCV侵染后烟粉虱成虫体内泛素蛋白含量的变化;饲喂抑制剂和注射双链RNA的方法抑制烟粉虱成虫体内蛋白酶体活性后,通过RT-qPCR测定其体内TYLCV含量的变化。【结果】烟粉虱成虫携带TYLCV后,泛素以及26S蛋白酶体亚基4、6B和β基因的表达量没有发生显著变化,体内游离泛素和缀合泛素的含量以及两者的比例也都没有显著改变,表明TYLCV侵染不会影响烟粉虱体内泛素-蛋白酶体的活性。但饲喂抑制剂(Bortezomib或MG132)或沉默Rpn11抑制蛋白酶体活性后,烟粉虱成虫体内的TYLCV含量显著升高。【结论】泛素-蛋白酶体系统对烟粉虱体内的TYLCV起负调控作用,该系统可能通过直接降解病毒或激活免疫反应等方式抑制病毒含量,进而帮助烟粉虱应对TYLCV带来的不利影响。

[ Aim ] Ubiquitination is an important reversible post-translational modification, which is involved in cell cycle, signal transduction, transcriptional regulation and immune response. However, the function of ubiquitin-proteasome system in virus transmission by insect vectors remains unknown. This study aims to explore the interactions between the ubiquitin-proteasome system of whitefly Bemisia tabaci and Tomato yellow leaf curl virus （TYLCV）. [ Methods ] The expression levels of ubiquitin and proteasome subunit genes in Bemisia tabaci adults feeding on TYLCV-infected and uninfected tomato plants were detected by RT-qPCR. Changes in the contents of free and conjugated ubiquitin proteins in B. tabaci adults after TYLCV infection were detected by Western blotting. After the ubiquitin-proteasome system was disrupted with specific inhibitors or dsRNA injection, changes in the TYLCV content inB. tabaci adults were detected by RT-qPCR. [ Results ] Carrying TYLCV did not lead to significant change in the expression levels of ubiquitin and 26S proteasome subunit 4, 6B and genes in B. tabaci adults, and had no influence on the contents of free ubiquitin and conjugated ubiquitin proteins and their ratio, suggesting that TYCLV has no effect on the ubiquitin-proteasome system of the whitefly. However, disrupting ubiquitin-proteasome system by specific inhibitors Bortezomib or MG132 or silencing Rpnl 1 by RNAi led to significant increase in the TYLCV content in B. tabaci adults. [ Conclusion ] Ubiquitin- proteasome system negatively regulates the TYLCV content in B. tabaci. Ubiquitin-proteasome system might help the whitefly to counteract the negative influence from TYLCV through degrading the virus directly or activating immune response.