In the previous paper published in 2017, we described the structure of Hox gene cluster of the ascidian, Halocynthia roretzi, and discussed the scenario for the disintegration of Hox gene clusters during evolution of ascidians. The description about the Hox gene cluster structure still represents the latest information, hence it has been left unchanged. In contrast, some points in Discussion, the description on the phylogenetic relationships among tunicates and the theoretical scenario for the disintegration of Hox gene cluster during evolution of ascidians, should be changed because the phylogenetic relationships among tunicates have recently been updated. The above mentioned points were made in accordance with the phylogenetic tree for tunicates based on the mitochondrial DNA sequences, which was the latest at the time of publication. In 2018, however, Kocot et al. and Delsuc et al. proposed new phylogenetic trees for tunicates based on a large number of nuclear gene sequences. The trees obtained by the two groups are essentially the same and different from the previous one in the phylogenetic positions of Appendicularia and Thaliacea, which leads to a change in the order of the emergence of ascidians and the Hox gene cluster disintegration during evolution of ascidians or tunicates. We add here a note to update the previous description on the phylogenetic relationships among tunicates and the theoretical scenario, including one Figure, so as to coincide with the new phylogenetic relationships among tunicates based on the nuclear gene sequences. The previous summarized conclusion remains unchanged: we suggest that the Hox gene cluster of the ancestral ascidian experienced extensive genome shuffling during the course of evolution to Hr and Ci. Nevertheless, some features are shared in Hox gene components and gene organization on the chromosomes, suggesting that Hox gene cluster disintegration in ascidians involved early events common to all ascidians and later lineage-specific events.

中文翻译：

---

注意：海鞘的 Hox 基因簇，Halocynthia roretzi，揭示了海鞘进化过程中集群解体的多个古老步骤

在2017年发表的上一篇论文中，我们描述了海鞘Hox基因簇Halocynthia roretzi的结构，并讨论了海鞘进化过程中Hox基因簇解体的情景。关于 Hox 基因簇结构的描述仍然代表最新信息，因此保持不变。相比之下，讨论中的一些观点，关于被囊类动物之间系统发育关系的描述以及海鞘进化过程中Hox基因簇解体的理论场景，应该改变，因为最近被囊类动物之间的系统发育关系已经更新。上述几点是根据基于线粒体DNA序列的被囊动物系统发育树提出的，这是出版时最新的。2018年，然而，Kocot 等人。和德尔苏克等人。提出了基于大量核基因序列的被囊类动物的新系统发育树。两组得到的树木在Appendicularia和Thaliacea的系统发育位置上与上一棵树基本相同和不同，这导致了海鞘出现顺序的变化和Hox基因簇在海鞘进化过程中的解体或被囊。我们在此添加一个注释来更新之前关于被囊类动物之间的系统发育关系的描述和理论场景，包括一个图，以便与基于核基因序列的被囊类动物之间新的系统发育关系相吻合。之前总结的结论不变：我们认为祖先海鞘的 Hox 基因簇在进化到 Hr 和 Ci 的过程中经历了广泛的基因组改组。尽管如此，Hox 基因成分和染色体上的基因组织具有一些共同特征，这表明海鞘中的 Hox 基因簇解体涉及所有海鞘共同的早期事件和后来的谱系特异性事件。