Emerging evidence shows that N6-methyladenosine (m6A) is a post-transcriptional RNA modification that plays a vital role in regulation of gene expression, fundamental biological processes, and physiological functions. To explore the effect of starvation on m6A methylation modification in the liver of Larimichthys crocea (L. crocea) under low temperatures, the livers of L. crocea from cold and cold + fasting groups were subjected to MeRIP-seq and RNA-seq using the NovaSeq 6000 platform. Compared to the cryogenic group, the expression of RNA methyltransferases mettl3 and mettl14 was upregulated, whereas that of demethylase fto and alkbh5 was downregulated in the starved cryogenic group. A Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis showed that the differentially m6A-modified genes were mainly enriched in steroid biosynthesis, DNA replication, ribosome biogenesis in eukaryotes, PPAR, ECM-receptor interaction, lysine degradation, phosphatidylinositol, and the MAPK signaling pathway, suggesting that L. crocea responds to starvation under low-temperature stress through m6A methylation modification-mediated cell growth, proliferation, innate immunity, and the maintenance of lipid homeostasis. This study advances understanding of the physiological response mechanism exerted by m6A methylation modification in starved L. crocea at low temperatures.

PIWI-interacting RNAs (piRNAs) are an emerging class of small RNAs which protect the animal germline genome against deleterious transposable elements. Nevertheless, the characteristics and sex-related expression patterns of piRNA in Collichthys lucidus remain unknown. In this study, we first performed systematic next-generation high-throughput sequencing in C. lucidus ovaries and testes. We identified 3,027,834 piRNAs across six gonad libraries. Of these, 2225 piRNAs were differently expressed between testes and ovaries; 1195 were upregulated and 1030 downregulated in the testes. Interestingly, the potential target genes of 208 differentially expressed piRNAs had sex-related functions, including germ cell development, gonad development, ovarian follicle development, gamete generation, spermatid development, and spermatogenesis. Moreover, these target genes are involved in the TGF-β, Wnt, MAPK, mTOR, VEGF, and PI3K-Akt pathways. Further, 10 piRNAs were derived from Nectin2 and Mea1, which play important roles in sexual reproduction, male gamete generation, and germ cell development. We also identified 5482 piRNA clusters across the gonads, among which 139 piRNA clusters were uniquely expressed in the testes and 98 in the ovaries. The expression of core sex-related piRNA was validated by real-time PCR. Overall, our findings provide significant insights into C. lucidus’ sex-related piRNAs.

Background: The visual system plays critical roles in fish feeding, predator avoidance, and reproduction, with the phototransduction pathway serving as the core molecular mechanism of visual signal transduction. This study represents the first systematic analysis of phototransduction-related genes in large yellow croaker (Larimichthys crocea). Methods: Bioinformatics, transcriptomic analysis, and RT-qPCR were used to identify phototransduction-related genes in large yellow croaker and analyze their developmental expression patterns and responses to different light spectra. Results: Thirty phototransduction-related genes were identified, including genes involved in light perception, signal amplification, and signal termination and recovery. Structural analyses indicated that these genes were highly conserved in teleosts. Most genes showed low expression during 1–7 days post-hatching (dph), increased expression during 7–24 dph, and stable expression during 24–35 dph. Collectively, these results identify 15–24 dph as a critical developmental window for visual system maturation in large yellow croaker larvae. Under different spectral treatments at 15 dph, phototransduction-related genes exhibited wavelength-dependent expression patterns. Under the present experimental conditions, relatively higher expression levels of most phototransduction-related genes were observed under blue- and green-light treatments, whereas relatively lower expression levels were observed under the red-light treatment. Key downstream genes, including gucy2f, guca1d, calml4a, and rgs9b, were significantly affected by different light spectra. Conclusions: This study revealed the developmental dynamics and spectral response characteristics of phototransduction-related genes in the large yellow croaker. These findings provide new insights into teleost visual development and light adaptation and provide a molecular basis for future studies aimed at optimizing light conditions during larval rearing in large yellow croaker aquaculture.