生物谷综合：近日，中国科学院动物研究所研究员康乐领导的研究组，在昆虫特有蛋白的鉴定中取得突破性进展。他们通过分析完全变态与不完全变态昆虫的基因组信息，并与其他真核生物的基因组信息进行比较，鉴定出51种昆虫特有蛋白，包括与环境胁迫和感受刺激相关的蛋白、表皮蛋白和气味结合蛋白等，揭示了昆虫在环境适应与信息交流方面的独特特征。相关论文发表在国际著名基因组学杂志《英国医学委员会·基因组学》（BMC Genomics）上。
康乐告诉《科学时报》记者，昆虫是世界上种类最多的高等生物类群，据估计世界上昆虫种类大约有100多万种。研究昆虫的基因组和蛋白质组学对生物多样性、农业和人类健康等具有重要意义。昆虫种类的多样性、行为和生理的多样性以及遗传的多样性在生物界中都是最高的，昆虫多样性的分化是对环境的适应和亿万年长期进化的结果。导致昆虫高度多样性的原因和内在的遗传机制并不完全清楚。昆虫特有蛋白是昆虫物种分化、行为习性和形态上区别于其他生物种类的重要特征，但到底哪些蛋白属于昆虫特有蛋白并不清楚。
这项研究的对象包括不完全变态的飞蝗，完全变态的果蝇、蜜蜂、埃及伊蚊和家蚕的基因组信息，并与主要的真核生物真菌、线虫、小鼠和人类的基因组进行了细致的比较。“我们成功鉴定了51种昆虫特有蛋白，其中许多是昆虫的表皮蛋白和气味结合蛋白。表皮蛋白与昆虫的蜕皮、变态等重要生理过程密切相关，而气味结合蛋白在昆虫寻找食物与配偶的过程中发挥重要作用，说明在昆虫的进化与分化过程中，对环境的适应与交流对于塑造昆虫的形态与生理特征起到了关键的作用。”康乐说，这项研究向世人揭示，昆虫尽管有着丰富多彩的外形和迥异的习性，但是造成这种多样性的原因，并不像人们原来认识的那样，即以为原因是昆虫拥有多样化的蛋白。
对这些蛋白的基因进行KaKs分析发现，大多数昆虫特有蛋白有很低的KaKs值，说明这些蛋白在进化过程中突变率低，能够为昆虫提供稳定的蛋白质组成。研究中通过比对发现，昆虫特有蛋白的基因序列具有较少的冗余，可能也为昆虫提供了优于其他真核生物的环境适应优势。“既比较稳定，也比较善于适应环境，昆虫的特有蛋白确实很有趣。对其功能的进一步验证，有助于科学家推测昆虫亿万年来在基因组与蛋白质组方面的进化过程。我们的研究证明，昆虫生命形式的多样性并不是通过增加大量不同的基因实现的。”康乐告诉记者。
国际同行对文章给出了高度评价，他们认为：“作者进行了一项十分值得赞扬的工作，成功鉴定出的昆虫特有蛋白，对研究昆虫进化具有重大的创新意义。”“这篇文章十分有趣地研究了昆虫的核心蛋白，而这些蛋白在哺乳动物、线虫和真菌中从未被发现过。”“作者推测了昆虫的基因组和蛋白质组是如何进化的，所有的分析十分细致，文章中的大量数据非常有意义，这是一个非常有趣的论题。”“昆虫与人类的生活息息相关，每年昆虫的危害都给农作物生产和人类健康造成很大损失，通过基因组学与蛋白质组学信息分析寻找昆虫特有蛋白，是发现昆虫防治新途径的重要手段，该项研究具有重要的理论价值与实际意义。”
原始出处：
BMC Genomics 2007, 8:93 doi:10.1186/1471-2164-8-93
published 4 April 2007
Identification and characterization of insect-specific proteins by genome data analysis
Guojie Zhang* 1 ,2 ,3 , Hongsheng Wang* 1 , Junjie Shi* 2 , Xiaoling Wang2 , Hongkun Zheng2 , Gane Ka-Shu Wong2 , Terry Clark4 , Wen Wang3 , Jun Wang2 ,5 and Le Kang1
1State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology Chinese Academy of Sciences, Haidian Beijing 100080, China
2Beijing Institute of Genomics of Chinese Academy of Sciences, Beijing Genomics Institute, Beijing 101300, China
3CAS-Max Plank Junior Research Group, Key Laboratory of Cellular and Molecular Evolution, Kunming Institute of Zoology, Chinese Academy of Science (CAS), Kunming, Yunnan 650223, China
4Department of Electrical Engineering and Computer Science, The University of Kansas, 2001 Eaton Hall, Lawrence, KS 66044, USA
5Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230, Odense M, Denmark
Abstract
Background
Insects constitute the vast majority of known species with their importance including biodiversity, agricultural, and human health concerns. It is likely that the successful adaptation of the Insecta clade depends on specific components in its proteome that give rise to specialized features. However, proteome determination is an intensive undertaking. Here we present results from a computational method that uses genome analysis to characterize insect and eukaryote proteomes as an approximation complementary to experimental approaches.
Results
Homologs in common to Drosophila melanogaster, Anopheles gambiae, Bombyx mori, Tribolium castaneum, and Apis mellifera were compared to the complete genomes of three non-insect eukaryotes (opisthokonts) Homo sapiens, Caenorhabditis elegans and Saccharomyces cerevisiae. This operation yielded 154 groups of orthologous proteins in Drosophila to be insect-specific homologs; 466 groups were determined to be common to eukaryotes (represented by three opisthokonts). ESTs from the hemimetabolous insect Locust migratoria were also considered in order to approximate their corresponding genes in the insect-specific homologs. Stress and stimulus response proteins were found to constitute a higher fraction in the insect-specific homologs than in the homologs common to eukaryotes.
Conclusion
The significant representation of stress response and stimulus response proteins in proteins determined to be insect-specific, along with specific cuticle and pheromone/odorant binding proteins, suggest that communication and adaptation to environments may distinguish insect evolution relative to other eukaryotes. The tendency for low Ka/Ks ratios in the insect-specific protein set suggests purifying selection pressure. The generally larger number of paralogs in the insect-specific proteins may indicate adaptation to environment changes. Instances in our insect-specific protein set have been arrived at through experiments reported in the literature, supporting the accuracy of our approach.
