加拿大英属哥伦比亚大学Patrick J. Keeling研究组发现了一类非光合捕食者生物与红藻的近源关系。这一研究成果于2019年8月8日发表在国际学术期刊《自然》上。

研究人员描述了一个新的真核门（Rhodelphidia），并利用系统基因组学，证明它是与红藻密切相关的姊妹。然而，这里描述的两种Rhodelphis物种的特征几乎与定义红藻的物种相反：它们是非光合作用的、具有基因丰富的基因组的鞭毛捕食者，同时其基因组缺乏可能参与血红素合成的质体。总体而言，这些发现改变了人们对红藻的起源和整个原始色素体生物进化的看法，因为这些发现表明捕食和光养的组合很好地融入了该类群的进化。

红藻（Rhodophyta）是原始色素体生物（Archaeplastida）的三个谱系之一，Archaeplastida是由真核生物中质体的主要内共生起源生物组成的群体。红藻是一个多样的、物种丰富的群体，其中的成员通常是光自养的，但具有一些高度衍生的特征：它们有相对较小的少内含子基因组、代谢减少，并缺乏与运动、鞭毛和中心粒相关的细胞骨架结构。这表明在它们的起源周围发生了明显的基因丢失；然而，其进化谱系很难重建，因为它们与其他原始色素体生物谱系有很大的不同，而且这些谱系之间的关系还不清楚。

附：英文原文

Title: Non-photosynthetic predators are sister to red algae

Author: Ryan M. R. Gawryluk, Denis V. Tikhonenkov, Elisabeth Hehenberger, Filip Husnik, Alexander P. Mylnikov, Patrick J. Keeling

Issue&Volume:  Volume 572 Issue 7768

Abstract: Rhodophyta (red algae) is one of three lineages of Archaeplastida, a supergroup that is united by the primary endosymbiotic origin of plastids in eukaryotes. Red algae are a diverse and species-rich group, members of which are typically photoautotrophic, but are united by a number of highly derived characteristics: they have relatively small intron-poor genomes, reduced metabolism and lack cytoskeletal structures that are associated with motility, flagella and centrioles. This suggests that marked gene loss occurred around their origin; however, this is difficult to reconstruct because they differ so much from the other archaeplastid lineages, and the relationships between these lineages are unclear. Here we describe the novel eukaryotic phylum Rhodelphidia and, using phylogenomics, demonstrate that it is a closely related sister to red algae. However, the characteristics of the two Rhodelphis species described here are nearly opposite to those that define red algae: they are non-photosynthetic, flagellate predators with gene-rich genomes, along with a relic genome-lacking primary plastid that probably participates in haem synthesis. Overall, these findings alter our views of the origins of Rhodophyta, and Archaeplastida evolution as a whole, as they indicate that mixotrophic feedingthat is, a combination of predation and phototrophypersisted well into the evolution of the group.

DOI: 10.1038/s41586-019-1398-6

Source: https://www.nature.com/articles/s41586-019-1398-6