Data from: Repurposed transcriptomic data facilitate discovery of innate immunity Toll-Like Receptor (TLR) genes across Lophotrochozoa

The growing volume of genomic data from across life represents opportunities for deriving valuable biological information from data that were initially collected for another purpose. Here, we use transcriptomes collected for phylogenomic studies to search for toll-like receptor (TLR) genes in poorly sampled lophotrochozoan clades (Annelida, Mollusca, Brachiopoda, Phoronida, and Entoprocta) and one ecdysozoan clade (Priapulida). TLR genes are involved in innate immunity across animals by recognizing potential microbial infection. They have an extracellular leucine-rich repeat (LRR) domain connected to a transmembrane domain and an intracellular toll/interleukin-1 receptor (TIR) domain. Consequently, these genes are important in initiating a signaling pathway to trigger defense. We found at least one TLR ortholog in all but two taxa examined, suggesting that a broad array of lophotrochozoans may have innate immune systems similar to those observed in vertebrates and arthropods. Comparison to the SMART database confirmed the presence of both the LRR and the TIR protein motifs characteristic of TLR genes. Because we looked at only one transcriptome per species, discovery of TLR genes was limited for most taxa. However, several TRL-like genes that vary in the number and placement of LRR domains were found in phoronids. Additionally, several contigs contained LRR domains but lacked TIR domains, suggesting they were not TLRs. Many of these LRR-containing contigs had other domains (e.g., immunoglobin) and are likely involved in innate immunity.

覆盖全生物类群的基因组数据规模持续增长，为从原本为其他目的采集的数据中挖掘有价值的生物学信息提供了全新契机。本研究利用为系统基因组学研究采集的转录组（transcriptome）数据，在采样覆盖度不足的冠轮动物类群（环节动物门Annelida、软体动物门Mollusca、腕足动物门Brachiopoda、帚虫动物门Phoronida及内肛动物门Entoprocta）与1个蜕皮动物类群（鳃曳动物门Priapulida）中搜寻Toll样受体（toll-like receptor, TLR）基因。Toll样受体基因可通过识别潜在微生物感染，参与所有动物类群的先天免疫过程。该类基因拥有与跨膜结构域（transmembrane domain）相连的胞外富含亮氨酸重复序列（leucine-rich repeat, LRR）结构域，以及胞内Toll/白介素-1受体（toll/interleukin-1 receptor, TIR）结构域。因此，这类基因在启动触发防御反应的信号通路中发挥关键作用。本研究仅在2个受试类群中未检测到至少1个TLR直向同源基因（ortholog），这表明绝大多数冠轮动物可能拥有与脊椎动物及节肢动物相似的先天免疫系统。与SMART数据库的比对分析证实，所有受试类群中均存在TLR基因标志性的LRR与TIR蛋白基序。由于本研究仅为每个物种设置1个转录组样本，多数类群的TLR基因发掘存在局限。不过，研究人员在帚虫动物中发现了数个LRR结构域数量与位置存在差异的类TLR基因。此外，数个重叠群（contig）包含LRR结构域但缺失TIR结构域，表明它们并非TLR基因。这类携带LRR结构域的重叠群中，多数还拥有其他结构域（如免疫球蛋白immunoglobulin），推测其同样参与先天免疫过程。