Hemimastigophora is a novel supra-kingdom-level lineage of Eukaryotes

Almost all eukaryote life forms have now been placed within one of five to eight supra-kingdom-level groups using molecular phylogenetics1,2,3,4. The ‘phylum’ Hemimastigophora is probably the most distinctive morphologically defined lineage that still awaits such a phylogenetic assignment. First observed in the nineteenth century, hemimastigotes are free-living predatory protists with two rows of flagella and a unique cell architecture5,6,7; to our knowledge, no molecular sequence data or cultures are currently available for this group. Here we report phylogenomic analyses based on high-coverage, cultivation-independent transcriptomics that place Hemimastigophora outside of all established eukaryote supergroups. They instead comprise an independent supra-kingdom-level lineage that most likely forms a sister clade to the ‘Diaphoretickes’ half of eukaryote diversity (that is, the ‘stramenopiles, alveolates and Rhizaria’ supergroup (Sar), Archaeplastida and Cryptista, as well as other majo...

目前，通过分子系统发育学（molecular phylogenetics）研究，几乎所有真核生物类群均已被划归至5至8个超界级类群之下。半鞭毛虫门（Hemimastigophora）则是目前最具辨识度的形态定义演化支，尚未被归入上述任一超界级类群。半鞭毛虫于19世纪首次被发现，是一类自由生活的掠食性原生生物，具有两列鞭毛与独特的细胞结构5,6,7；据我们所知，目前尚无该类群的分子序列数据或培养菌株可供研究。本研究基于高覆盖度、非培养依赖的转录组学（transcriptomics）数据开展系统基因组分析，结果显示半鞭毛虫门并不属于任何已确立的真核生物超类群。该类群实为独立的超界级演化支，极有可能与真核生物多样性中"双鞭毛生物总界（Diaphoretickes）"分支构成姊妹支系——该分支涵盖SAR超类群（Stramenopiles, Alveolates, Rhizaria）、原始色素体生物（Archaeplastida）、隐藻类群（Cryptista）以及其他主要[...]