Project description:The blue bat star, a highly adaptive species in the East Sea of Korea, has displayed remarkable success in adapting to recent climate change. The genetic mechanisms behind this success were not well-understood, prompting our report on the first chromosome-level assembly of the Patiria genus. We assembled the genome using Nanopore and Illumina sequences, yielding a total length of 615 Mb and a scaffold N50 of 24,204,423 bp. Hi-C analysis allowed us to anchor the scaffold sequences onto 22 pseudochromosomes. K-mer based analysis revealed 5.16% heterozygosity rate of the genome, higher than any previously reported echinoderm species. Our transposable element analysis exposed a substantial number of genome-wide retrotransposons and DNA transposons. These results offer valuable resources for understanding the evolutionary mechanisms behind P. pectinifera's successful adaptation in fluctuating environments.
Project description:Ontogeny of the immune system is a fundamental immunology issue. One indicator of immune system maturation is the establishment of the immunological self, which describes the ability of the immune system to distinguish allogeneic individuals (allorecognition ability). However, the timing of immune system maturation during invertebrate ontogeny is poorly understood. In the sea star Patiria pectinifera, cells that have dissociated from the embryos and larvae are able to reconstruct larvae. This reconstruction phenomenon is possible because of a lack of allorecognition capability in the larval immune system, which facilitates the formation of an allogeneic chimera. In this study, we revealed that the adult immune cells of P. pectinifera (coelomocytes) have allorecognition ability. Based on a hypothesis that allorecognition ability is acquired before and after metamorphosis, we conducted detailed morphological observations and survival time analysis of metamorphosis-induced chimeric larvae. The results showed that all allogeneic chimeras died within approximately two weeks to one month of reaching the juvenile stage. In these chimeras, the majority of the epidermal cell layer was lost and the mesenchymal region expanded, but cell death appeared enhanced in the digestive tract. These results indicate that the immunological self of P. pectinifera is established post-metamorphosis during the juvenile stage. This is the first study to identify the timing of immune system maturation during echinodermal ontogenesis. As well as establishing P. pectinifera as an excellent model for studies on self- and non-self-recognition, this study enhances our understanding of the ontogeny of the immune system in invertebrates.