Unveiling Gene Expression Dynamics during Early Embryogenesis in Cynoglossus semilaevis: A Transcriptomic Perspective.

Commencing with sperm-egg fusion, the early stages of metazoan development include the cleavage and formation of blastula and gastrula. These early embryonic events play a crucial role in ontogeny and are accompanied by a dramatic remodeling of the gene network, particularly encompassing the maternal-to-zygotic transition. Nonetheless, the gene expression dynamics governing early embryogenesis remain unclear in most metazoan lineages. We conducted transcriptomic profiling on two types of gametes (oocytes and sperms) and early embryos (ranging from the four-cell to the gastrula stage) of an economically valuable flatfish-the Chinese tongue sole Cynoglossus semilaevis (Pleuronectiformes: Cynoglossidae). Comparative transcriptome analysis revealed that large-scale zygotic genome activation (ZGA) occurs in the blastula stage, aligning with previous findings in zebrafish. Through the comparison of the most abundant transcripts identified in each sample and the functional analysis of co-expression modules, we unveiled distinct functional enrichments across different gametes/developmental stages: actin- and immune-related functions in sperms; mitosis, transcription inhibition, and mitochondrial function in oocytes and in pre-ZGA embryos (four- to 1000-cell stage); and organ development in post-ZGA embryos (blastula and gastrula). These results provide insights into the intricate transcriptional regulation of early embryonic development in Cynoglossidae fish and expand our knowledge of developmental constraints in vertebrates.

The complete mitochondrial genome of Cynoglossus interruptus and its novel rearrangement (Pleuronectiformes: Cynoglossidae).

The complete mitochondrial genome was determined for the Cynoglossus interruptus belonging to the family Cynoglossidae. The length of the complete mitochondrial genome is 17,262 bp, consisting of 13 protein-coding genes, 22 tRNA genes, two rRNA genes, and a control region. The gene rearrangement related to tRNAGln and a control region gene were found, forming the gene order of CR-Ile-Gln-Met. Phylogenetic analysis using mitochondrial genomes of 12 species showed that C. interruptus formed a well-supported monophyletic group with other Cynoglossus species.

Gene rearrangements in the mitochondrial genome of robust tonguefish, Cynoglossus robustus (Pleuronectiformes: Cynoglossidae) and a comparative analysis with other Cynoglossus fishes.

The complete mitochondrial genome was determined for the Robust tonguefish Cynoglossus robustus belonging to the family Cynoglossidae. The length of the complete mitochondrial genome is 16,720 bp, consisting of 13 protein-coding genes, 22 tRNA genes, two rRNA genes, and a control region. Rearrangements of the tRNAGln and a control region gene were found and tRNAGln is translocated from the light to the heavy strand. Phylogenetic analysis using mitochondrial genomes of 12 species showed that C. robustus formed a well-supported monophyletic group with other Cynoglossus species.

The complete mitochondrial genome of Cynoglossus joyneri (Teleostei: Pleuronectiformes).

The complete mitochondrial genome of a commercially important sea fish Cynoglossus joyneri was sequenced and annotated. The 16,941 bp-long genome contained 13 protein-coding genes, 2 ribosomal RNAs, 22 transfer RNAs, and a control region. Phylogenetic analysis indicated that C. joyneri is a sister group with C. sinicus and C. bilineatus, and corroborated the proposed paraphyly of Cynoglossus genus.