Comprehensive analysis of Metacrinus rotundus full length transcriptome.

Modern stalked crinoids, an important group of echinoderms, represent the ancestral mode of crinoids, and studying their evolution is key to understanding the evolution of echinoderms. In this study, we selected Metacrinus rotundus, a species of modern stalked crinoids, for investigation. We generated M. rotundus transcripts using Pacific Biosciences single-molecule real-time (SMRT) long-read sequencing technology. A total of 160,849 full-length (FL) transcripts were captured by Iso-Seq, with a mean length of 2,470 bp. Of these FL transcripts, 110,859 were well-annotated based on public database. A portion of transcripts remained unannotated, representing potential novel genes for M. rotundus. Additionally, we identified 71,740 long-noncoding RNA (LncRNAs), 57,548 simple sequence repeats (SSRs), and 3,486 hypothetical transcript factors (TFs). By comparing Holothuroid and Echinoid, M. rotundus have a higher proportion of zf-CCCH and TF_Otx within TFs, as well as trinucleotide SSRs within SSRs. Notably, transposable elements (TEs) make up a large proportion of the full-length transcriptome of M. rotundus, with RNA transposons being the largest class of annotated TEs. Our study enhances understanding of the characteristics of M. rotundus transcriptome and provides a valuable genetic resource for further studies on adaptive evolution in this species, as well as in other crinoids.