Biology subjects

Omori, Y.

Publications and source records attributed to Omori, Y..

3 recordsLinked to original sources

bioRxiv2026

Transcriptome-based genome-wide analysis reveals hybridization dynamics and genetic structure of Japanese giant salamanders

AbstractsThe Japanese giant salamander (Andrias japonicus), an apex predator and a Special Natural Monument in Japan, is threatened by hybridization with introduced Chinese giant salamanders (Andrias davidianus). This hybridization has caused genetic introgression and expansion of hybrid populations, posing a serious conservation risk. Because morphological identification of hybrids is occasionally unreliable and current genetic methods rely on limited markers, a genome-wide approach is required. However, the extremely large genome ([~]50 Gb) of giant salamanders has hindered whole-genome analyses. In this study, we conducted transcriptome-based analyses of Japanese giant salamanders, Chinese giant salamanders, and their hybrids, generating RNA-seq data from 34 individuals. A total of over 419,000 SNP candidates were identified, from which 4,457 high-confidence SNPs in highly expressed genes were selected for analysis. Population structure analyses for Nabari colony revealed that hybrid individuals form two major groups, corresponding to different degrees of genetic contribution from Japanese and Chinese lineages. Most hybrids were inferred to be F2 or backcross individuals, while F1 hybrids were rare. Mitochondrial analysis indicated that all hybrids possessed Japanese-type mitochondrial genome, suggesting male-mediated introgression from Chinese salamanders. Differential expression analysis revealed enhanced stress-response pathways in hybrids and stronger antiviral responses in Japanese individuals. Using the axolotl genome as a reference, we constructed a virtual chromosomal map, identifying large haplotype blocks and supporting recent hybridization with limited recombination. This study provides a genome-wide framework for understanding hybridization dynamics and supports future conservation and evolutionary studies.

ecology↗

bioRxiv2019

Sex chromosome and sex locus characterization in the goldfish, Carassius auratus

BackgroundGoldfish is an important model for various areas of research, including neural development and behavior and a species of significant importance in aquaculture, especially as an ornamental species. It has a male heterogametic (XX/XY) sex determination system that relies on both genetic and environmental factors, with high temperatures being able to produce female-to-male sex reversal. Little, however, is currently known on the molecular basis of genetic sex determination in this important cyprinid model. We used sequencing approaches to better characterize sex determination and sex-chromosomes in goldfish. ResultsOur results confirmed that sex determination in goldfish is a mix of environmental and genetic factors and that its sex determination system is male heterogametic (XX/XY). Using reduced representation (RAD-seq) and whole genome (pool-seq) approaches, we characterized sex-linked polymorphisms and developed male specific genetic markers. These male specific markers were used to distinguish sex-reversed XX neomales from XY males and to demonstrate that XX female-to-male sex reversal could even occur at a relatively low rearing temperature (18{degrees}C), for which sex reversal has been previously shown to be close to zero. We also characterized a relatively large non-recombining region ([~]11.7 Mb) on goldfish linkage group 22 (LG22) that contained a high-density of male-biased genetic polymorphisms. This large LG22 region harbors 373 genes, including a single candidate as a potential master sex gene, i.e., the anti-Mullerian hormone gene (amh). However, no sex-linked polymorphisms were detected in the goldfish amh gene or its 5 kb proximal promoter sequence. ConclusionsThese results show that goldfish have a relatively large sex locus on LG22, which is likely the goldfish Y chromosome. The presence of a few XX males even at low temperature also suggests that other environmental factors in addition to temperature could trigger female-to-male sex reversal. Finally, we also developed sex-linked genetic markers in goldfish, which will be important for future research on sex determination and aquaculture applications in this species.

genomics↗

bioRxiv2018

De Novo assembly of the goldfish (Carassius auratus) genome and the evolution of genes after whole genome duplication

For over a thousand years throughout Asia, the common goldfish (Carassius auratus) was raised for both food and as an ornamental pet. Selective breeding over more than 500 years has created a wide array of body and pigmentation variation particularly valued by ornamental fish enthusiasts. As a very close relative of the common carp (Cyprinus carpio), goldfish shares the recent genome duplication that occurred approximately 14-16 million years ago (mya) in their common ancestor. The combination of centuries of breeding and a wide array of interesting body morphologies is an exciting opportunity to link genotype to phenotype as well as understanding the dynamics of genome evolution and speciation. Here we generated a high-quality draft sequence of a \"Wakin\" goldfish using 71X PacBio long-reads. We identified 70,324 coding genes and more than 11,000 non-coding transcripts. We found that the two sub-genomes in goldfish retained extensive synteny and collinearity between goldfish and zebrafish. However, \"ohnologous\" genes were lost quickly after the carp whole-genome duplication, and the expression of 30% of the retained duplicated gene diverged significantly across seven tissues sampled. Loss of sequence identity and/or exons determined the divergence of the expression across all tissues, while loss of conserved, non-coding elements determined expression variance between different tissues. This draft assembly also provides an important resource for comparative genomics with the very commonly used zebrafish model (Danio rerio), and for understanding the underlying genetic causes of goldfish variants.

genomics↗