State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, 19A Yuquan Road, Beijing 100049, China.
State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, 19A Yuquan Road, Beijing 100049, China.
Int J Biol Macromol. 2023 Jun 15;240:124480. doi: 10.1016/j.ijbiomac.2023.124480. Epub 2023 Apr 15.
Water flux across cells predominantly occurs through the pore formed by the aquaporin channels. Since water balance is one of the most important challenges to terrestrial animals, aquaporin evolution and diversity is known to play roles in animal terrestrialisation. Arachnids (Arthropoda: Chelicerata: Arachnida) are the second most diverse group and represent the pioneer land colonists in animals; however, there remains no thorough investigation on aquaporin evolution and diversity in this evolutionarily important lineage. Here we reported a phylogenetic study of aquaporin evolution and diversity using genomic data from 116 arachnid species covering almost all (15/16) extant orders. A previously unrecognised subfamily related to aquaporin-4 (i.e. Aqp4-like subfamily) via phylogenetic analysis was identified, suggesting certain underestimate of the arachnid aquaporin diversity in earlier studies probably due to limited taxonomic sampling. Further analysis indicates that this subfamily emerged deep within the life tree of arthropods. Gene tree of another Aqp4-like subfamily (PripL) shows an unexpected basal split between acariform mites (Acariformes) and other arachnids. A closer inspection demonstrated that the PripL evolved quickly and has been under differential selection pressure in acariform mites. Evidence is provided that the evolutionarily ancient Glp subfamily (i.e. aquaglyceroporin) is significantly expanded in terrestrial arachnids compared with their marine relatives. Finally, in spite of the phylogenetic diversity, there exists conservation of some exons in size, functional domain, and intron-insertion phase: an 81-bp and a 218-bp exon, respectively, in apq4-like and glp genes across Eumetazoa lineages including arachnids and human beings. Both exons encode the carboxyl-terminal NPA motif, implying the coding and splicing pressure during hundreds of million years of animal evolution. Hypotheses were tested to explore the possible link between these findings and arachnid terrestrialisation.
水主要通过水通道形成的孔在细胞间流动。由于水平衡是陆地动物面临的最重要挑战之一，因此水通道蛋白的进化和多样性被认为在动物的陆地化过程中发挥了作用。蛛形纲动物（节肢动物门：螯肢亚门：蛛形纲）是第二大类群，是动物中最早的陆地殖民者；然而，在这个进化上重要的谱系中，水通道蛋白的进化和多样性仍然没有得到彻底的研究。在这里，我们使用来自 116 种蛛形纲动物的基因组数据进行了水通道蛋白进化和多样性的系统发育研究，几乎涵盖了所有（16 个中的 15 个）现存的目。通过系统发育分析，发现了一个以前未被识别的与水通道蛋白-4 相关的亚家族（即 Aqp4 样亚家族），这表明在早期研究中，由于分类学采样有限，蛛形纲动物的水通道蛋白多样性可能被低估。进一步的分析表明，这个亚家族出现在节肢动物生命树的深处。另一个 Aqp4 样亚家族（PripL）的基因树显示，在蜱螨目（蜱螨目）和其他蛛形纲动物之间存在一个意外的基部分裂。仔细检查表明，PripL 进化迅速，在蜱螨目动物中受到了不同的选择压力。有证据表明，古老的 Glp 亚家族（即水通道甘油蛋白）在陆地蛛形纲动物中显著扩张，与它们的海洋亲缘相比。最后，尽管在系统发育上具有多样性，但在大小、功能域和内含子插入相位上的一些外显子仍然保守：apq4 样和 glp 基因在包括蛛形纲动物和人类在内的真后生动物谱系中分别有 81 个碱基对和 218 个碱基对的外显子。这两个外显子都编码羧基末端 NPA 基序，这意味着在数亿年的动物进化过程中存在编码和剪接压力。提出了一些假设来探索这些发现与蛛形纲动物陆地化之间的可能联系。
