Comparison of diploid and triploid Carassius auratus provides insights into adaptation to environmental change

Comparative analysis of intestinal microbiota composition and transcriptome in diploid and triploid Carassius auratus

Polyploidy and the microbiome are crucial factors in how a host organism responds to disease. However, little is known about how triploidization and microbiome affect the immune response and disease resistance in the fish host. Therefore, this study aims to identify the relationship between intestinal microbiota composition, transcriptome changes, and disease resistance in triploid Carassius auratus (3nCC). In China's central Dongting lake water system, diploid (2nCC) and triploid Carassius auratus were collected, then 16S rRNA and mRNA sequencing were used to examine the microbes and gene expression in the intestines. 16S rRNA sequencing demonstrated that triploidization altered intestinal richness, as well as the diversity of commensal bacteria in 3nCC. In addition, the abundance of the genus Vibrio in 3nCC was increased compared to 2nCC (P < 0.05). Furthermore, differential expression analysis of 3nCC revealed profound up-regulation of 293 transcripts, while 324 were down-regulated. Several differentially expressed transcripts were related to the immune response pathway in 3nCC, including NLRP3, LY9, PNMA1, MR1, PELI1, NOTCH2, NFIL3, and NLRC4. Taken together, triploidization can alter bacteria composition and abundance, which can in turn result in changes in expression of genes. This study offers an opportunity for deciphering the molecular mechanism underlying disease resistance after triploidization.

Transcriptomic and Metabolomic Analyses Provide Insights into the Growth and Development Advantages of Triploid Apostichopus japonicus

Polyploid breeding is widely used in aquaculture as an important area of new research. We have previously grown Apostichopus japonicus triploids with a growth advantage. The body length, body weight, and aestivation time of triploid and diploid A. japonicus were measured in this study, and the transcriptome and metabolome were used to examine the growth advantage of triploids A. japonicus. The results showed that the proportion of triploid A. japonicus with a body length of 6-12 cm and 12-18 cm was significantly higher than that of diploid A. japonicus, and triploid A. japonicus had a shorter aestivation time (39 days) than diploid (63 days). We discovered 3296 differentially expressed genes (DEGs); 13 DEGs (for example, cyclin-dependent kinase 2) related to growth advantage, immune regulation, and energy storage were screened as potential candidates. According to Gene Ontology (GO) enrichment analysis, DEGs were significantly enriched in the cytoplasm (cellular component), ATP binding process (molecular function), oxidation-reduction process (biological process), and other pathways. According to the Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment data, DEGs were significantly enriched in ribosome production and other areas. We discovered 414 significant differential metabolites (SDMs), with 11 important SDMs (for example, nocodazole) linked to a growth advantage. SDMs are significantly enriched in metabolic pathways, as well as other pathways, according to the KEGG enrichment results. According to a combined transcriptome and metabolome analysis, 6 DEGs have regulatory relationships with 11 SDMs, which act on 11 metabolic pathways together. Our results further enrich the biological data of triploid A. japonicus and provide useful resources for genetic improvement of this species.

Diverse transcriptional patterns of homoeologous recombinant transcripts in triploid fish (Cyprinidae)

Homoeologous recombination (HR), the exchange of homoeologous chromosomes, contributes to subgenome adaptation to diverse environments by producing various phenotypes. However, the potential relevance of HR and innate immunity is rarely described in triploid cyprinid fish species. In our study, two allotriploid genotypes (R₂C and RC₂), whose innate immunity was stronger than their inbred parents (Carassius auratus red var. and Cyprinus carpio L.), were obtained from backcrossing between male allotetraploids of C. auratus red var.×C. carpio L. and females of their two inbred parents, respectively. The work detected 140 HRs shared between the two triploids at the genomic level. Further, transcriptions of 54 homoeologous recombinant genes (HRGs) in R₂C and 65 HRGs in RC₂ were detected using both Illumina and PacBio data. Finally, by comparing expressed recombinant reads to total expressed reads in each of the genes, a range of 0.1%-10% was observed in most of the 99-193 HRGs, of which six recombinant genes were classified as "response to stimulus". These results not only provide a novel way to predict HRs in allopolyploids based on cross prediction at both genomic and transcriptional levels, but also insight into the potential relationship between HRs related to innate immunity and adaptation of the triploids and allotetraploids.

MicroRNA expression profile analysis of skin immune response in crucian carp (Carassius auratus) infected by Aeromonas hydrophila

MicroRNAs (miRNAs) are non-coding RNA molecules that regulate gene expression in fish, but its regulatory mechanism of the skin mucosal immune response remains poorly understood. In order to investigate the immunological role of miRNAs, three sRNA libraries (mSC, mST1, mST2) from skin samples of crucian carp (Carassiusauratus) infected with Aeromonas hydrophila at three time points (0, 6 and 12 hpi) were constructed and examined using Illumina Hiseq 2000 platform. All of the identified miRNA, rRNA and tRNA were 69444 (13.39%), 29550 (5.70%) and 10704 (2.06%) in skin, respectively. At 6 and 12 hpi, 829 and 856 miRNAs were differentially expressed, respectively. Among these DEMs, 53 known and 10 novel miRNAs were all significantly differentially expressed during early infection (p < 0.01). GO and KEGG enrichment analyses revealed that 118111 target-genes were primarily involved in cellular process, metabolic process, biological regulation and stress response, such as antigen processing and presentation, complement and coagulation cascades, phagosome, MAPK, TLR, NF-κB and JAK-STAT signaling pathways. These results will help to elucidate the mechanism of miRNAs involved in the skin mucosal immune response of crucian carp against Aeromonas hydrophila infection.