八肋游仆虫微管蛋白基因家族的鉴定及进化分析

为了系统分析八肋游仆虫(Euplotes octocarinatus)微管蛋白基因家族, 从八肋游仆虫大核基因组中共鉴定得到20个微管蛋白基因, 基于同源比对及系统进化分析, 将其归入α、β、γ、δ、ε及η六个微管蛋白亚家族; 多序列比对及Western blot结果显示八肋游仆虫η微管蛋白基因在翻译过程中需发生一次+1位编程性核糖体移码, 其移码位点为AAA-TAA; 所有自由生纤毛虫都含有多个α和β微管蛋白基因亚型, 可能用于组成不同的微管结构。研究为后续深入探讨八肋游仆虫微管蛋白的生物学功能及微管多样性奠定了基础。

IDENTIFICATION AND EVOLUTION ANALYSIS OF TUBULIN SUPERFAMILY GENES IN EUPLOTES OCTOCARINATUS

Microtubules represent one of the major cytoskeletal filament systems of all eukaryotic cells. They play a key role in spatial arrangement of the organelles, intracellular transport, nuclear and cell division, and ciliar motility. Ciliates are ideal model organisms for studying the functional diversity of tubulins. Here, a total of 20 tubulin genes were identified in the macronuclear genome of the ciliate Euplotes octocarinatus. Based on ortholog comparisons and phylogenetic analysis, these genes were clustered into six groups: α-, β-, γ-, δ-, ε- and η-tubulins. Sequence analysis and western blots suggested that the η-tubulin gene of E. octocarinatus required a +1 programmed ribosomal frameshifting to produce complete protein product. The slippery sequence is AAATAAT. We further systematically identified tubulin genes from 9 other ciliates and compared them with E. octocarinatus. The α- and β-tubulins of all investigated free-living ciliates are encoded by multigene families, and each tubulin isotype may be used to form distinct tubulin structures. Phylogenetic analysis showed that α- and β-tubulin genes underwent multiple independent duplications and losses in ciliate. Our study lays a foundation for studying the biological function of tubulins and exploring the mechanisms of microtubule diversity.