Partial purification and characterization of a methyl-parathion resistance-associated general esterase in Diabrotica virgifera virgifera (Coleoptera: Chrysomelidae)

Increased hydrolytic metabolism of organophosphate insecticides has been associated with resistance among Nebraska western corn rootworm populations. In this study, resistance-associated esterases were partially purified by differential centrifugation, ion exchange, and hydroxyapatite column chromatography, with a final purification factor of 100-fold and recovery of approximately 10%. Kinetic analysis of the partially purified enzyme indicated that the K_m of the group II esterases was identical for the two populations, although V_max was consistently threefold higher in the resistant population. A putative esterase, DvvII, was further purified to homogeneity by preparative polyacrylamide gel electrophoresis. DvvII is a monomer with a molecular weight of approximately 66 kDa, although three distinct isoforms with similar pIs were evident based on isoelectric focusing gel electrophoresis. Immunoassays with the Myzus persicae E4 antiserum indicated that group II esterases from D. v. virgifera were cross-reactive and expressed at much higher titers in the resistant population relative to the susceptible counterpart. These results suggest that the resistance is likely associated with overproduction of an esterase isozyme in resistant D. v. virgifera populations.     

基于MaxEnt模型预测气候变化下玉米根萤叶甲在中国的潜在地理分布

为评估不同气候条件下玉米根萤叶甲Diabrotica virgifera virgifera在我国的潜在地理分布情况及适生区的空间格局变化趋势,通过筛选影响该虫分布的关键环境变量并基于其在全球的分布数据,运用MaxEnt模型和ArcGIS软件预测其在历史和未来气候情景下的潜在地理分布范围和适生区空间格局变化。结果表明,所构建MaxEnt模型的受试者工作特征 （receiver operating characteristic, ROC）曲线下面积（area under curve, AUC）平均为0.960,说明模型预测结果为优秀,具有较高的可信度。关键气候变量中最冷月最低温对玉米根萤叶甲的潜在地理分布具有十分重要的影响,累积贡献率为44.5%。历史气候条件下,玉米根萤叶甲的总适生区面积占我国陆地总面积的23.78%,高适生区主要分布于我国河南、湖北、陕西、甘肃、重庆、四川和云南等省市。未来气候情景下,玉米根萤叶甲在我国的总适生区面积略有减少,整体上呈现出南部收缩、北部扩张的趋势,原中南部的中、高适生区逐步转变为低适生区或非适生区。玉米根萤叶甲在我国的适生区较为广泛,适生范围涵盖多个重要玉米产区,对玉米安全生产威胁较大,应给予足够的重视,严防该虫传入我国。     

四种钙结合蛋白基因在沙葱萤叶甲幼虫生长发育中的作用

为明确沙葱萤叶甲Galeruca daurica钙结合蛋白基因的功能,利用本实验室组装的沙葱萤叶甲转录组数据库鉴定钙结合蛋白基因序列,采用RNA干扰（RNA interference,RNAi）技术沉默沙葱萤叶甲3龄幼虫体内钙调蛋白（calmodulin,CaM）、钙网蛋白（calreticulin,CRT）、类钙磷蛋白（calcyphosine-like,CAPSL）和类肌钙蛋白C（troponin C-like,TnCl）共4种钙结合蛋白基因,观察幼虫发育历期、存活率、体重及蛹重的变化;应用实时荧光定量PCR测定干扰效率。结果表明,共筛选到41条编码钙结合蛋白的基因序列,选取4条具有完整开放阅读框的钙结合蛋白基因序列进行后续研究。4种钙结合蛋白基因的干扰效率从高到低依次为CAPSL（94.4%）、TnCl（76.2%）、CRT（70.5%）和CaM（54.5%）;干扰效率最高的时间分别为干扰后第4、2、6和2天。沉默CAPSL后,沙葱萤叶甲幼虫体重显著降低了21.0%~34.9%,存活率显著下降了53.5%,发育历期显著缩短了15.1%,蛹重显著降低了15.8%。沉默TnCl后,沙葱萤叶甲幼虫体重显著降低了10.5%~25.0%,存活率显著下降了19.1%,蛹重显著降低了11.0%,而对发育历期无显著影响。沉默CaM后,沙葱萤叶甲幼虫体重显著降低了5.9%~6.6%,存活率显著降低了8.7%,而幼虫发育历期和蛹重无显著变化。沉默CRT后,沙葱萤叶甲幼虫体重、蛹重、存活率和发育历期均无显著变化。表明CAPSL、TnCl和CaM在沙葱萤叶甲幼虫生长发育过程中发挥着重要作用,而CRT可能未参与沙葱萤叶甲幼虫生长发育的调控过程。     

沙葱萤叶甲表皮蛋白基因GdAbd的克隆及对温度胁迫的响应

为揭示沙葱萤叶甲Galeruca daurica表皮蛋白基因GdAbd在其应对温度胁迫中的作用,采用RACE技术克隆表皮蛋白基因GdAbd的cDNA全长序列,并进行生物信息学分析;利用实时荧光定量(qPCR)技术比较GdAbd经不同温度处理1 h及25℃恢复30 min后在沙葱萤叶甲2龄幼虫体内的表达水平。结果表明,GdAbd基因全长708 bp(GenBank登录号:MG874710),开放阅读框为477 bp,编码158个氨基酸;蛋白预测分子量为16.98 kD,等电点为4.26;编码蛋白具有典型的表皮蛋白RR保守结构域,属于RR-2亚族;具有1个跨膜结构和1个信号肽。同源序列比对和系统发育分析表明,GdAbd与马铃薯甲虫Leptinotarsa decemlineata SgAbd-4的同源性最高,氨基酸序列一致性达50.63%。qPCR检测结果表明,与25℃对照相比,GdAbd基因表达水平在-10～5℃低温胁迫时未发生显著变化,而在35℃高温胁迫时发生显著上调;-10、-5和0℃低温胁迫后25℃恢复30 min可诱导GdAbd显著上调表达,但5℃低温和35℃高温胁迫处理与对照差异不显著。说明短时低温胁迫不能显著影响GdAbd表达,但胁迫后回温可诱导其上调表达。     

温度胁迫下沙葱萤叶甲小热激蛋白基因GdHsp20.6的克隆及表达分析

为明确小热激蛋白在沙葱萤叶甲Galeruca daurica应对温度胁迫中的作用,采用PCR方法克隆沙葱萤叶甲小热激蛋白基因Hsp20（GdHsp20.6）完整的开放阅读框（open reading frame,ORF）序列,应用在线软件对GdHsp20.6基因进行生物信息学分析,通过原核表达技术诱导表达及纯化其编码蛋白,并通过实时荧光定量PCR（real-time quantitative PCR,RT-qPCR）技术分析不同温度胁迫下GdHsp20.6基因的表达量。结果显示,GdHsp20.6基因ORF序列长度为543 bp,编码180个氨基酸,预测分子量为20.6 kD,无跨膜区和信号肽。GdHsp20.6氨基酸序列有高度保守的α-结构域。GdHsp20.6氨基酸序列与其它鞘翅目昆虫的Hsp20氨基酸序列有较高的一致性,其中与花绒寄甲Dastarcus helophoroides的Hsp20.99氨基酸序列的一致性最高,为63%。GdHsp20.6基因在大肠杆菌Escherichia coli BL21（DE3）细胞系中成功表达,经异丙基-β-D-硫代吡喃半乳糖苷（isopropyl-β-d-thiogalactoside,IPTG）诱导后GdHsp20.6蛋白成功表达,十二烷基硫酸钠-聚丙烯酰胺凝胶电泳（sodium dodecyl sulfate-polyacrylamide gel electrophoresis,SDS-PAGE）和Western-blot分析表明融合蛋白大小与预测大小一致,并纯化获得了纯度较高的目的蛋白GdHsp20.6。低温（-10~5℃）和高温（35~40℃）处理1 h以及处理后25℃恢复30 min均能诱导GdHsp20.6基因表达上调,并且0℃处理30~120 min也能诱导GdHsp20.6基因表达上调。表明GdHsp20.6基因在沙葱萤叶甲应对低温和高温胁迫中可能起着重要作用。     

Metabolic resistance mechanisms to phosalone in the common pistachio psyllid, Agonoscena pistaciae (Hem.: Psyllidae)

The common pistachio psyllid, Agonoscena pistaciae, is the most damaging pest of pistachio in Iran, and is generally controlled by insecticides belonging to various classes especially, phosalone. The toxicity of phosalone in nine populations of the pest was assayed using the residual contact vial and insect-dip methods. The bioassay results showed significant discrepancy in susceptibility to phosalone among the populations. Resistance ratio of the populations to the susceptible population ranged from 3.3 to 11.3. The synergistic effects of TPP, PBO and DEM were evaluated on the susceptible and the most resistant population to determine the involvement of esterases, mixed function oxidases and glutathione S-transferases in resistance mechanisms, respectively. The level of resistance to phosalone in the resistant population was suppressed by TPP, PBO and DEM, suggesting that the resistance to phosalone is mainly caused by esterase detoxification. Biochemical enzyme assays revealed that esterase, glutathione S-transferase and cytochrome P450 monooxygenase activities in the resistant population was higher than that in the susceptible. Glutathione-S-transferases play a minor role in the resistance of the pest to phosalone.     

香豆素类化合物对朱砂叶螨的触杀活性及定量构效关系研究

采用玻片浸渍法,测定并筛选了25种具有代表性的香豆素类化合物对朱砂叶螨Tetranychus cinnabarinus雌成螨的触杀活性,并构建了一个预测能力较强的定量构效关系(QSAR)模型。结果表明:所有供试化合物对朱砂叶螨均具有触杀活性,且随着处理时间的延长活性升高。处理48 h后,LC50值低于1000 mg/L的化合物有8个,分别是3-(2-苯并咪唑)-7-(二乙氨基)香豆素(1)、3-(2-苯并噻唑)-7-(二乙氨基)香豆素(2)、3-氨基香豆素(3)、3-乙酰基香豆素(4)、4-甲氧基香豆素(5)、6-硝基香豆素(8)、6,7-二甲氧基香豆素(13)和7,8-二羟基香豆素(21),其中化合物1、2、3、5和13的杀螨活性优于药剂对照螺螨酯或与其活性相当;活性最好的化合物为13,处理48 h和72 h后LC50值分别为284.8和122.2 mg/L,其毒力约为螺螨酯的2倍。通过计算得到25种香豆素类化合物的34种物化参数,以此为描述子,经过SPSS相关性剔除、逐步回归分析和校正,得到一个以扭转力、取向力、总能量和分子半径为自变量的QSAR模型,该模型复相关系数R达到0.987,复判定系数R2也达到0.967,通过F检验证明上述模型具有较高的预测能力。