美国加州大学伯克利分校Daniel S. Rokhsar等研究人员合作发现，古老的基因联系支持栉水母为其他动物的姐妹。相关论文于2023年5月17日在线发表于国际学术期刊《自然》。

研究人员表示，演化生物学的一个核心问题是海绵动物或栉水母（梳状水母）是否是所有其他动物的姐妹群体。这些可供选择的系统发育假说意味着复杂的神经系统和其他动物特有性状演化的不同情况。基于形态学特征和日益广泛的基因序列收集的传统系统发育方法还不能明确地回答这个问题。

研究人员开发了染色体尺度的基因联结，也称为共线性，作为解决这一问题的系统发育特征。研究人员报告了一种栉水母和两种海洋海绵以及三种单细胞动物的亲属（一种领鞭毛虫、一种丝状变形虫和一种ichthyosporean）的新染色体尺度基因组，作为系统发育分析的外群。研究人员发现在动物和它们的单细胞近亲之间存在着古老的共线性关系。栉水母和单细胞真核生物共享祖先的后生模式，而海绵动物、双壳动物和网状动物共享衍生的染色体重排。保守的共线性特征将海绵动物与两侧对称动物、刺胞动物和扁盘动物结合在一个单系支系中，将栉水母排除在外，使栉水母成为所有其他动物的姐妹组。海绵动物、两侧对称动物和刺胞动物共有的共线性模式是罕见的、不可逆的染色体融合和混合事件的结果，为栉水母的姐妹假说提供了有力和明确的系统发育支持。这些发现为解决深层次的、顽固的系统发育问题提供了一个新的框架，并对人们理解动物演化有意义。

附：英文原文

Title: Ancient gene linkages support ctenophores as sister to other animals

Author: Schultz, Darrin T., Haddock, Steven H. D., Bredeson, Jessen V., Green, Richard E., Simakov, Oleg, Rokhsar, Daniel S.

Issue&Volume: 2023-05-17

Abstract: A central question in evolutionary biology is whether sponges or ctenophores (comb jellies) are the sister group to all other animals. These alternative phylogenetic hypotheses imply different scenarios for the evolution of complex neural systems and other animal-specific traits1,2,3,4,5,6. Conventional phylogenetic approaches based on morphological characters and increasingly extensive gene sequence collections have not been able to definitively answer this question7,8,9,10,11. Here we develop chromosome-scale gene linkage, also known as synteny, as a phylogenetic character for resolving this question12. We report new chromosome-scale genomes for a ctenophore and two marine sponges, and for three unicellular relatives of animals (a choanoflagellate, a filasterean amoeba and an ichthyosporean) that serve as outgroups for phylogenetic analysis. We find ancient syntenies that are conserved between animals and their close unicellular relatives. Ctenophores and unicellular eukaryotes share ancestral metazoan patterns, whereas sponges, bilaterians, and cnidarians share derived chromosomal rearrangements. Conserved syntenic characters unite sponges with bilaterians, cnidarians, and placozoans in a monophyletic clade to the exclusion of ctenophores, placing ctenophores as the sister group to all other animals. The patterns of synteny shared by sponges, bilaterians, and cnidarians are the result of rare and irreversible chromosome fusion-and-mixing events that provide robust and unambiguous phylogenetic support for the ctenophore-sister hypothesis. These findings provide a new framework for resolving deep, recalcitrant phylogenetic problems and have implications for our understanding of animal evolution.

DOI: 10.1038/s41586-023-05936-6

Source: https://www.nature.com/articles/s41586-023-05936-6