背景:神经系统起源于原口和子宫口分裂之前,超过6亿年前。四个动物门(Cnidaria,胎盘动物,黄蜂,Porifera)在分裂之前分歧,研究这些门可以为我们提供有关神经系统进化的重要信息。这里,我们已经注释了二十种属于Hexacorallia或Ceriantharia(Anthozoa:Cnidaria)亚类的神经肽前激素基因,使用37个可公开访问的基因组或转录组数据库。学习六角形很重要,因为它们是用于开发的多功能实验室模型(例如,Nematostellavectensis)和共生(例如,Exaiptasiadiaphana),也是著名的珊瑚礁建造者。
结果:我们发现,每个六口或天蚕物种都含有5至10个神经肽前激素原基因。许多这些前激素原含有多个拷贝的未成熟神经肽,可以是多达50个相同或相似的神经肽序列的拷贝。我们还发现前激素原仅包含一个位于信号序列之后的神经肽序列。它们的实例是以序列RWamide终止的神经肽(Antho-RWamides)。大多数神经肽序列的N-末端被焦谷氨酰(pQ)或一个或多个脯氨酸残基保护。而它们的C端由酰胺基保护。以前,我们从由不寻常的L-3-苯基酰基保护的N-末端保护的六环中分离并测序了小神经肽。在我们目前的分析中,我们发现这些N-苯基酰基肽衍生自直接位于前激素原信号序列之后的N-苯基丙氨酰肽。N-苯基酰基-肽似乎仅限于六角形Actiniaria,在其他刺胞动物中不存在。另一方面,(1)神经肽Antho-RFamide(pQGRFamide);(2)具有C末端序列GLWamide的肽;(3)具有X1PRX2amide共有序列的四肽(最常见的是GPRGamide)在Hexacorallia中普遍存在。
结论:我们发现GRFamide,GLWamide,和所有测试的Hexacorallia中的X1PRX2酰胺肽。以前,我们在长方体中也发现了这三种神经肽,Scyphozoa,和Staurozoa,表明这些神经肽起源于普通的刺胞祖先,在进化上是古老的。除了这些普遍存在的神经肽,其他神经肽似乎仅限于特定的刺胞动物顺序或亚类。
BACKGROUND: Nervous systems originated before the split of Proto- and Deuterostomia, more than 600 million years ago. Four animal phyla (Cnidaria, Placozoa, Ctenophora, Porifera) diverged before this split and studying these phyla could give us important information on the evolution of the nervous system. Here, we have annotated the neuropeptide preprohormone genes of twenty species belonging to the subclass Hexacorallia or Ceriantharia (Anthozoa: Cnidaria), using thirty-seven publicly accessible genome or transcriptome databases. Studying hexacorals is important, because they are versatile laboratory models for development (e.g., Nematostella vectensis) and symbiosis (e.g., Exaiptasia diaphana) and also are prominent reef-builders.
RESULTS: We found that each hexacoral or ceriantharian species contains five to ten neuropeptide preprohormone genes. Many of these preprohormones contain multiple copies of immature neuropeptides, which can be up to 50 copies of identical or similar neuropeptide sequences. We also discovered preprohormones that only contained one neuropeptide sequence positioned directly after the signal sequence. Examples of them are neuropeptides that terminate with the sequence RWamide (the Antho-RWamides). Most neuropeptide sequences are N-terminally protected by pyroglutamyl (pQ) or one or more prolyl residues, while they are C-terminally protected by an amide group. Previously, we isolated and sequenced small neuropeptides from hexacorals that were N-terminally protected by an unusual L-3-phenyllactyl group. In our current analysis, we found that these N-phenyllactyl-peptides are derived from N-phenylalanyl-peptides located directly after the signal sequence of the preprohormone. The N-phenyllactyl- peptides appear to be confined to the hexacorallian order Actiniaria and do not occur in other cnidarians. On the other hand, (1) the neuropeptide Antho-RFamide (pQGRFamide); (2) peptides with the C-terminal sequence GLWamide; and (3) tetrapeptides with the X1PRX2amide consensus sequence (most frequently GPRGamide) are ubiquitous in Hexacorallia.
CONCLUSIONS: We found GRFamide, GLWamide, and X1PRX2amide peptides in all tested Hexacorallia. Previously, we discovered these three neuropeptide classes also in Cubozoa, Scyphozoa, and Staurozoa, indicating that these neuropeptides originated in the common cnidarian ancestor and are evolutionarily ancient. In addition to these ubiquitous neuropeptides, other neuropeptides appear to be confined to specific cnidarian orders or subclasses.