Chromosome-level genome assembly of Korean holoparasitic plants, Orobanche coerulescens.

Orobanche coerulescens is a parasitic plant that cannot complete its life cycle without a host and is incapable of photosynthesis. The habitats of O. coerulescens span the coasts of Korea and its volcanic islands, Ulleungdo and Dokdo. Those on the volcanic islands exhibit morphological differences and have distinct hosts compared to those on the peninsula. The family of Orobanchaceae, encompassing both autotrophic and parasitic species, serves as a model for evolutionary studies of parasitic states. However, there are limited genome assemblies for the Orobanche genus. In our study, we produced approximately 100x ONT long reads to construct a chromosome-level genome of O. coerulescens. The resulting assembly has a total size of 3,648 Mb with an N50 value of 195 Mb, and 82.0% of BUSCO genes were identified as complete. Results of the repeat annotation revealed that 86.3% of the genome consisted of repeat elements, and 29,395 protein-coding genes were annotated. This chromosome-level genome will be an important biological resource for conserving biodiversity and further understanding parasitic plants.

The first high-quality genome assembly and annotation of Patiria pectinifera.

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.

Distinctive origin and evolution of endemic thistle of Korean volcanic island: Structural organization and phylogenetic relationships with complete chloroplast genome.

Unlike other Cirsium in Korea, Cirsium nipponicum (Island thistle) is distributed only on Ulleung Island, a volcanic island off the east coast of the Korean Peninsula, and a unique thistle with none or very small thorns. Although many researchers have questioned the origin and evolution of C. nipponicum, there is not much genomic information to estimate it. We thus assembled the complete chloroplast of C. nipponicum and reconstructed the phylogenetic relationships within the genus Cirsium. The chloroplast genome was 152,586 bp, encoding 133 genes consisting of 8 rRNA genes, 37 tRNA genes, and 88 protein-coding genes. We found 833 polymorphic sites and eight highly variable regions in chloroplast genomes of six Cirsium species by calculating nucleotide diversity, as well as 18 specific variable regions distinguished C. nipponicum from other Cirsium. As a result of phylogenetic analysis, C. nipponicum was closer to C. arvense and C. vulgare than native Cirsium in Korea: C. rhinoceros and C. japonicum. These results indicate that C. nipponicum is likely introduced through the north Eurasian root, not the mainland, and evolved independently in Ulleung Island. This study contributes to further understanding the evolutionary process and the biodiversity conservation of C. nipponicum on Ulleung Island.

Chromosome-level genome assembly of Plazaster borealis sheds light on the morphogenesis of multiarmed starfish and its regenerative capacity.

BACKGROUND: Plazaster borealis has a unique morphology, displaying multiple arms with a clear distinction between disk and arms, rather than displaying pentaradial symmetry, a remarkable characteristic of echinoderms. Herein we report the first chromosome-level reference genome of P. borealis and an essential tool to further investigate the basis of the divergent morphology. FINDINGS: In total, 57.76 Gb of a long read and 70.83 Gb of short-read data were generated to assemble a de novo 561-Mb reference genome of P. borealis, and Hi-C sequencing data (57.47 Gb) were used for scaffolding into 22 chromosomal scaffolds comprising 92.38% of the genome. The genome completeness estimated by BUSCO was 98.0% using the metazoan set, indicating a high-quality assembly. Through the comparative genome analysis, we identified evolutionary accelerated genes known to be involved in morphogenesis and regeneration, suggesting their potential role in shaping body pattern and capacity of regeneration. CONCLUSION: This first chromosome-level genome assembly of P. borealis provides fundamental insights into echinoderm biology, as well as the genomic mechanism underlying its unique morphology and regeneration.