枫长镰管蚜Drepanosiphum platanoidis是少数几种不分泌E-β-法尼烯(E-β-farnesene,EBF)的蚜虫之一。ApisOBP3是首个被鉴定的特异结合EBF的昆虫气味结合蛋白,来自于豌豆蚜Acyrthosiphum pisum。本研究通过基因克隆技术,在枫长镰管蚜体内获得2个表达ApisOBP3类似蛋白的cDNA序列,长度均为426bp,其中,5'末端的69bp为信号肽编码序列。编码的成熟蛋白分别命名为DplaOBP3-1和DplaOBP3-2,两个蛋白均由119个氨基酸残基组成,序列一致性为95.8%。与ApisOBP3的序列一致性分别为95.8%和98.3%。DplaOBP3-1,DplaOBP3-2及ApisOBP33个蛋白具有数量和位置完全一致的6个保守的半胱氨酸残基。以测得3D结构的马德拉蜚蠊Leucophaea maderae的信息素结合蛋白LmadPBP为模板比较建模,结果显示两个蛋白在疏水中心均具有与ApisOBP3一致的关键疏水残基及芳香族氨基酸残基Tyr84。利用四臂嗅觉仪测定枫长镰管蚜的嗅觉行为反应,结果显示:枫长镰管蚜残体挥发物及外源EBF对该蚜均有显著的驱避作用(P=0.01)。本研究提示,枫长镰管蚜具有种内报警信息素,该蚜残体挥发物即为其种内报警信息素;枫长镰管蚜尽管并不分泌EBF,但具有表达2种OBP3蛋白的基因,并可识别环境中的EBF且对其作出行为反应。
ApisOBP3 from Acyrthosiphum pisum was known as its affinity to E-β-farnesene(EBF),and the volatile substances released by Drepanosiphum platanoidis contain no EBF which is a conventional component secreted by most of aphids.In this study,two odorant binding proteins named as DplaOBP3-1 and DplaOBP3-2 sharing high identities(95.8% and 98.32%,respectively) with ApisOBP3 were identified in D.platanoidis.The lengths of coding sequences of both DplaOBP3-1 and DplaOBP3-2 are 426 bp with 69 bp coding for signal peptide at the 5' end.DplaOBP3-1,DplaOBP3-2 and ApisOBP3 share 6 highly conserved cysteine residues at the same position among sequences.Based on the 3D structure of LmadPBP,a pheromone binding protein from cockroach Leucophaea maderae,we modeled the structures of DplaOBP3-1 and DplaOBP3-2,and all the five hydrophobic amino acids and the aromatic amino acid residue,Tyr84,located in the binding cavity probably participating in interacting with ligands have their counterparts in the structure of ApisOBP3.Further,four-arm olfactometer assay showed that D.platanoidis were significantly repelled by both EBF and crushed aphids(P=0.01).The results suggest that volatiles from fresh crushed bodies could be the intraspecies alarm pheromone in D.platanoidis;D.platanoidis are repelled by allogenetic EBF whereas they never release EBF.