10月27日,BMC evolutionary biology杂志在线发表了中国科学院水生生物研究所原生动物功能基因组学学科组博士生熊杰完成的论文。
该研究鉴定得到了165个四膜虫ATP结合盒转运蛋白基因，是目前已报道的含该类基因最多的真核生物；对这些基因进行系统发育和保守内含子分析、以及与同为纤毛虫的草履虫进行比较，发现众多的四膜虫ATP结合盒转运蛋白是在四膜虫与草履虫分化后通过基因复制扩张产生的（约800 Mya）；进一步对它们的基因表达谱和表达进化模式的分析表明，部分四膜虫ATP结合盒转运蛋白基因在发生基因复制后其表达和功能也发生了分歧，同时这些基因在基因组中保留下来的模式则更多地符合新功能化和剂量平衡的模型。
此项研究是该学科组继去年完成四膜虫细胞色素P450基因家族分子进化工作（BMC genomics）之后，对四膜虫中与环境感知和响应相关的多基因家族进化模式和功能演化分析的新进展，进一步验证了他们提出的四膜虫是研究该类多基因家族分子进化良好真核生物的观点。
该研究得到了国家自然科学基金项目和中科院知识创新重要方向性项目的资助。（生物谷Bioon.com）
生物谷推荐英文摘要：
BMC Evolutionary Biology 2010, 10:330doi:10.1186/1471-2148-10-330
Genome-wide identification and evolution of ATP-binding cassette transporters in the ciliate Tetrahymena thermophila: A case of functional divergence in a multigene family
Jie Xiong , Lifang Feng , Dongxia Yuan , Chengjie Fu and Wei Miao
Background
In eukaryotes, ABC transporters that utilize the energy of ATP hydrolysis to expel cellular substrates into the environment are responsible for most of the efflux from cells. Many members of the superfamily of ABC transporters have been linked with resistance to multiple drugs or toxins. Owing to their medical and toxicological importance, members of the ABC superfamily have been studied in several model organisms and warrant examination in newly sequenced genomes.
Results
A total of 165 ABC transporter genes, constituting a highly expanded superfamily relative to its size in other eukaryotes, were identified in the macronuclear genome of the ciliate Tetrahymena thermophila. Based on ortholog comparisons, phylogenetic topologies and intron characterizations, each highly expanded ABC transporter family of T. thermophila was classified into several distinct groups, and hypotheses about their evolutionary relationships are presented. A comprehensive microarray analysis revealed divergent expression patterns among the members of the ABC transporter superfamily during different states of physiology and development. Many of the relatively recently formed duplicate pairs within individual ABC transporter families exhibit significantly different expression patterns. Further analysis showed that multiple mechanisms have led to functional divergence that is responsible for the preservation of duplicated genes.
Conclusion
Gene duplications have resulted in an extensive expansion of the superfamily of ABC transporters in the Tetrahymena genome, making it the largest example of its kind reported in any organism to date. Multiple independent duplications and subsequent divergence contributed to the formation of different families of ABC transporter genes. Many of the members within a gene family exhibit different expression patterns. The combination of gene duplication followed by both sequence divergence and acquisition of new patterns of expression likely plays a role in the adaptation of Tetrahymena to its environment.
