《生命科学》 2010, 22(12): 1215-1228
摘 要：
摘 要：生命的进化依赖于其周边的化学环境，通过对这些化学物质的感受，适应环境，生命得以繁衍。直到现在，各种有机体仍然保留着这种古老而有效的感知方式。飞蝗是世界性的农业大害虫，其很多行为如远距离迁飞、聚集、取食、产卵等是其造成灾害的重要生物学因素，而这些行为都与其感受化学信息相关。深入研究飞蝗感受化学信息的机制对于揭示生物感受化学信息的分子和细胞机制的多样性，设计出可以激发或钝化这些蛋白质的引诱剂或忌避剂，进而防治害虫等具有重要意义。该文主要介绍了该课题组在东亚飞蝗(Locusta migratoria manilesis)感受化学信息机制方面的一些进展。通过超微结构研究发现在飞蝗触角上至少有毛形、锥形、腔锥形和刺形4种类型的化学感受器，明确了各种感受器的超微结构特征，其中毛形和锥形是重要的嗅觉感受器。以此为基础，单感受器电位记录试验结果表明飞蝗触角上的毛形感受器至少有7种功能亚型，其中5种亚型每个感受器含有2个神经原，2种亚型每个感受器含有3种神经原。初步明确了飞蝗毛形感受器神经原对一些化学信息的编码特征。在飞蝗的触角中鉴定出了飞蝗气味分子结合蛋白(LmigOBP1)，通过免疫细胞化学定位实验证明该蛋白特异表达在飞蝗毛形和锥形感受器的淋巴液中，而且在胚胎即将孵化前就开始表达，此后在各个胚后发育时期都表达，说明该蛋白可能参与飞蝗胚后发育的所有阶段的嗅觉活动。采用荧光竞争结合实验方法，明确了LmigOBP1对有15~17个碳原子的直链的脂肪族醇、酯或醛有很强的亲和力，说明该蛋白有结合特异性。采用生物信息学技术模拟出了更为合理的LmigOBP1的三维结构，通过对接实验，提出了飞蝗气味分子结合蛋白结合腔中可能参与结合十五醇的氨基酸残基。之后通过定点氨基酸突变将59位的丝氨酸、74位的天冬酰氨和87位的缬氨酸分别用丙氨酸替代获得三个突变体蛋白(S59A、N74A、V87A)，通过与野生型蛋白荧光竞争结合实验结果的比较，发现突变体S59A的结合模式与野生型相同，N74A几乎丧失了全部结合能力，而V87A则对有些气味分子的结合能力有较大改变。因此，位于结合腔开口处的74位天冬酰氨是该蛋白的重要结合位点，而位于结合腔底部的87位缬氨酸也是结合位点。结合前人的结果，我们首次提出了昆虫气味分子结合蛋白依赖位于结合腔开口处的亲水性氨基酸实现对气味分子的初始识别的假说。文章最后对今后研究的一些重点进行了讨论。
关键词：飞蝗；化学感受；嗅觉神经原；化学信息编码；气味分子结合蛋白；结合位点；结合特异性；结合行为
中图分类号：S433.2， Q617 文献标识码：A
Abstract: Abstract: Organisms evolve with their ability sensing environmental chemicals， and they still maintain this old and efficient receptive ability. As one of the organisms， locusts， most important pest insect to crops world wide， is with this ability sense exogenous chemicals to cause important behaviors， such as migration， aggregation， foraging and courtship tightly related with locust plagues. A detailed knowledge of chemoreception in locusts at the molecular level will help understanding the diversity of cellular and molecular mechanisms of organisms， as well as designing novel repellents or attractants for locust control. Here we present our latest results of research on locust chemoreception in Locusta migratoria manilesis. We have identified 4 types of chemosensilla， s. trichoid， s. basiconic， s. ceoloconic and s. chaetic on antenna. Their ultrastructure indicates that trichoid and basiconic sensilla are olfactory. Functional studies， using single sensillum recording， indicated that trichoid sensilla may be divided into 7 subtypes， 5 containing 2 neurons， the other two containing 3. All these 16 cells have been characterized in terms of odorant specificity. Locust odorant binding protein (LmigOBP1) is specifically expressed in the lymph of trichoid and basiconic sensilla， as shown by using immunocytochemical study. Its synthesis starts just before hatching and continues through post-embryo life， indicating that it might play important roles in chemical sensing. LmigOBP1 shows high affinity to 15-17 carbon linear aliphatic compounds. We have also performed docking experiments on a three-dimensional model of the protein. These simulations showed that more than 16 amino acids may be involved in the binding of 1-pentadecanol. Two amino acid residues in particular， N74 at entrance of the binding pocket， and V87 at inner bottom of the pocket might be more important for the binding activity of this protein， as shown by experiments with specific mutants. Here we propose that the region at entrance of the binding pocket plays a very important role in the initial recognition of ligands. Finally， we give some aspects of study in future.
Key words: locust; chemoreception; olfactory sensory neuron; coding; odorant-binding proteins; specificity; binding site; binding behavior
