Project description:Channel catfish (Ictalurus punctatus) and tra catfish (Pangasianodon hypophthalmus) both belong to the order Siluriformes. Channel catfish does not possess an air-breathing organ (ABO), and thus cannot breathe in the air, while tra catfish is a facultative air-breather and use the swim bladder as its air-breathing organ, which provides for aerial breathing in low oxygen conditions. Tra and channel catfish serve as a great comparative model for studying the transition of life from water to terrestrial living, as well as for understanding genes that are crucial for development of the swim bladder and the function of air-breathing in tra catfish. We selected seven developmental stages in tra catfish for RNA-Seq analysis based on their transition to a stage that could live at 0 ppm oxygen. More than 587 million sequencing clean reads were generated in tra catfish, and a total of 21, 448 unique genes were detected. A comparative genomic analysis was conducted between channel catfish and tra catfish. Gene expression analysis was performed for these tra catfish specific genes. Hypoxia challenge and microtomy experiments collectively suggested that there are critical timepoints for the development of the air-breathing function and swim bladder development stages in tra catfish. Key genes were identified to be the best candidates of genes related to the air-breathing ability in tra catfish. This study provides a large data resource for functional genomic studies in air-breathing function in tra catfish, and sheds light on the adaption of aquatic organisms to the terrestrial environment.
Project description:Channel catfish and blue catfish represent two economically important freshwater aquaculture species in the United States. Our study aims to investigate the gene expression differences between these two catfish species by high-throughput RNA sequencing to understand their associated phenotypic differences in growth and disease resistant. Our transcriptomic analyses provide some insights into gene function differences between the two species and the molecular basis of channel catfish growth advantage in the tank culture environment.
Project description:The hybrid between female channel catfish (Ictalurus punctatus) and male blue catfish (Ictalurus furcatus) is superior in feed conversion, disease resistance, carcass yield, and harvestability compared to both parental species. However, heterosis and heterobeltiosis only occur in pond culture, and channel catfish grow much faster than the other genetic types in small culture units. This environment-dependent heterosis is intriguing, but the underlying genetic mechanisms are not well understood. In this study, phenotypic characterization and transcriptomic analyses were performed in the channel catfish, blue catfish, and their reciprocal F1s reared in tanks. The results showed that the channel catfish is superior in growth-related morphometrics, presumably due to significantly lower innate immune function, as investigated by reduced lysozyme activity and alternative complement activity. RNA-seq analysis revealed that genes involved in fatty acid metabolism/transport are significantly upregulated in channel catfish compared to blue catfish and hybrids, which also contributes to the growth phenotype. Interestingly, hybrids have a 40-80% elevation in blood glucose than the parental species, which can be explained by a phenomenon called transgressive expression (overexpression/underexpression in F1s than the parental species). A total of 1,140 transgressive genes were identified in F1 hybrids, indicating that 8.5% of the transcriptome displayed transgressive expression. Transgressive genes upregulated in F1s are enriched for glycan degradation function, directly related to the increase in blood glucose level. This study is the first to explore molecular mechanisms of environment-dependent hetero-sis/heterobeltiosis in a vertebrate species and sheds light on the regulation and evolution of heterosis vs. hybrid incompatibility.
Project description:Cryopreservation of blue catfish sperm can cause variable embryo hatch rates, which is the limiting factor for hybrid catfish breeding. In this study, we investigated gene expression changes caused by cryopreservation using transcriptome profiles of fresh sperm samples and cryopreserved sperm from the same set of blue catfish.
