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.

全球范围内日益增长的各类生物基因组数据，为从最初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契机。本研究利用为系统发育组学研究构建的转录组数据，对采样不足的冠轮动物类群（环节动物门、软体动物门、腕足动物门、帚虫动物门、内肛动物门）以及1个蜕皮动物类群（曳鳃动物门）中的Toll样受体（toll-like receptor, TLR）基因进行检索。Toll样受体可通过识别潜在的微生物感染，在各类动物的先天免疫过程中发挥作用。该类基因拥有与跨膜结构域相连的胞外富亮氨酸重复（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具有重要意义。本研究在除2个受试类群外的所有类群中均发现了至少1个TLR直系同源基因，这表明绝大多数冠轮动物可能拥有与脊椎动物和节肢动物相似的先天免疫系统。通过与SMART数据库比对，我们确认了TLR基因特有的LRR和TIR蛋白基序均存在于所检测的序列中。由于本研究仅对每个物种的1个转录组进行分析，多数类群的TLR基因检出存在局限。不过，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TLR样基因。此外，部分重叠群仅包含LRR结构域而缺失TIR结构域，提示其并非TLR基因。这类含LRR结构域的重叠群中，多数还包含其他结构域（如免疫球蛋白结构域），推测其同样参与先天免疫过程。