近日，中国科学院昆明动物研究所张亚平院士指导的博士研究生吴东东及其合作者系统地获得了疟蚊基因组中的类胰蛋白酶丝氨酸蛋白酶基因，并和黑腹果蝇的基因相比较，发现该家族在蚊子基因组中经历过适应性扩张。该类基因的表达水平在吸血之后显著升高，并且扩张的基因相对于进化稳定的基因的表达量升高较高。同时，正选择分析表明，系统发育扩张基因所受正选择作用的位点主要分布在与蛋白酶抑制结合区域。这些分析表明，类胰蛋白酶丝氨酸蛋白酶基因对蚊子吸血这一特性的适应性进化起着重要作用。该研究具有重要的意义。

蚊子是挥之不去，给人类健康带来许多威胁的害虫，其主要通过吸血来传播各种疾病，如疟疾、丝虫病、登革热、黄热病等。类胰蛋白酶丝氨酸蛋白酶(trypsin-like serine protease)是一广泛存在于动物界的基因家族，主要行使消化功能，而其在蚊子消化血液的过程中起到重要作用。伴随着吸血过程，蚊子体内会发生很多生理上的变化，如基因表达量的升高或降低。研究这类发生变化的相关基因或元件有助于揭示蚊子吸血的机制，进而寻找到控制蚊子传播疾病的有效方法。

推荐原始出处：

Molecular Biology and Evolution, doi:10.1093/molbev/msp139

A profound role for the expansion of trypsin-like serine protease family in the evolution of hematophagy in mosquito

Dong-Dong Wu1,3, Guo-Dong Wang1,3, David M Irwin4,5 and Ya-Ping Zhang1,2,3,*

1 State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, China
2 Laboratory for Conservation and Utilization of Bio-resource, Yunnan University, Kunming 650091, China
3 Graduate School of the Chinese Academy of Sciences, Beijing, China
4 Department of Laboratory Medicine and Pathobiology, University of Toronto, Ontario, Canada
5 Banting and Best Diabetes Centre, University of Toronto, Ontario, Canada

The trypsin-like serine protease (Tryp_SPc) family is ubiquitous in animals, and plays diverse roles, especially in the digestive system, in different phyla. In the mosquito, some Tryp_SPc proteases make important contributions to the digestion of the blood meal. Here, we have defined the complete Tryp_SPc gene repertoire in the genome of the malaria mosquito, a repertoire that has expanded remarkably compared to that of Drosophila. Phylogenetic analysis also indicates that the large scale lineage-specific expansion occurred leading to mosquitoes. Expression of Tryp_SPc genes elevates after a blood meal, and the expression level of genes that belong to subfamilies that specifically expanded on the mosquito lineage increased significantly more than genes that belong to subfamilies that did not expand in number, suggesting a profound role for the Tryp_SPc genes, especially the expanded subfamilies, in the hematophagous trait of the mosquito. The mosquito Tryp_SPc genes are mostly distributed in a tandem manner on chromosomes, suggesting a role for tandem duplication in the expansion of the subfamilies. Furthermore, evidence for positive selection was found for some genes. Structural modeling indicates that the positively selected sites locate to the surface that is conjugated by protein inhibitors. Our results suggest that the expansion and diversification of the Tryp_SPc domain family in mosquito was driven by positive selection and helps to explain the adaptive hematophagy of the mosquito.