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1. Environment-Dependent Heterosis and Transgressive Gene Expression in Reciprocal Hybrids between the Channel Catfish Ictalurus punctatus and the Blue Catfish Ictalurus furcatus

   https://doi.org/10.3390/biology11010117  

   Wang, Haolong; Bruce, Timothy J.; Su, Baofeng; Li, Shangjia; Dunham, Rex A.; Wang, Xu (January 2022, Biology)

   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 1140 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 heterosis/heterobeltiosis in a vertebrate species and sheds light on the regulation and evolution of heterosis vs. hybrid incompatibility. 

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2. Establishment of a Practical Sperm Cryopreservation Pathway for the Axolotl (Ambystoma mexicanum): A Community-Level Approach to Germplasm Repository Development

   https://doi.org/10.3390/ani14020206  

   Coxe, Nicholas; Liu, Yue; Arregui, Lucía; Upton, Rose; Bodenstein, Sarah; Voss, Steven Randal; Gutierrez-Wing, Maria T; Tiersch, Terrence R (January 2024, Animals)

   The axolotl (Ambystoma mexicanum) draws great attention around the world for its importance as a biomedical research model, but housing and maintaining live animals is increasingly expensive and risky as new transgenic lines are developed. The goal of this work was to develop an initial practical pathway for sperm cryopreservation to support germplasm repository development. The present study assembled a pathway through the investigation of axolotl sperm collection by stripping, refrigerated storage in various osmotic pressures, cryopreservation in various cryoprotectants, and in vitro fertilization using thawed sperm. By the stripping of males, 25–800 µL of sperm fluid was collected at concentrations of 1.6 × 106 to 8.9 × 107 sperm/mL. Sperm remained motile for 5 d in Hanks’ Balanced Salt Solution (HBSS) at osmolalities of 100–600 mOsm/kg. Sperm cryopreserved in 0.25 mL French straws at 20 °C/min in a final concentration of 5% DMFA plus 200 mM trehalose and thawed at 25 °C for 15 s resulted in 52 ± 12% total post-thaw motility. In six in vitro fertilization trials, 20% of eggs tested with thawed sperm continued to develop to stage 7–8 after 24 h, and a third of those embryos (58) hatched. This work is the first report of successful production of axolotl offspring with cryopreserved sperm, providing a general framework for pathway development to establish Ambystoma germplasm repositories for future research and applications. 

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3. Chromosome-level assembly and annotation of the blue catfish Ictalurus furcatus , an aquaculture species for hybrid catfish reproduction, epigenetics, and heterosis studies

   https://doi.org/10.1093/gigascience/giac070  

   Wang, Haolong; Su, Baofeng; Butts, Ian A. E.; Dunham, Rex A.; Wang, Xu (July 2022, GigaScience)

   Abstract BackgroundThe blue catfish is of great value in aquaculture and recreational fisheries. The F1 hybrids of female channel catfish (Ictalurus punctatus) × male blue catfish (Ictalurusfurcatus) have been the primary driver of US catfish production in recent years because of superior growth, survival, and carcass yield. The channel–blue hybrid also provides an excellent model to investigate molecular mechanisms of environment-dependent heterosis. However, transcriptome and methylome studies suffered from low alignment rates to the channel catfish genome due to divergence, and the genome resources for blue catfish are not publicly available. ResultsThe blue catfish genome assembly is 841.86 Mbp in length with excellent continuity (8.6 Mbp contig N50, 28.2 Mbp scaffold N50) and completeness (98.6% Eukaryota and 97.0% Actinopterygii BUSCO). A total of 30,971 protein-coding genes were predicted, of which 21,781 were supported by RNA sequencing evidence. Phylogenomic analyses revealed that it diverged from channel catfish approximately 9 million years ago with 15.7 million fixed nucleotide differences. The within-species single-nucleotide polymorphism (SNP) density is 0.32% between the most aquaculturally important blue catfish strains (D&B and Rio Grande). Gene family analysis discovered significant expansion of immune-related families in the blue catfish lineage, which may contribute to disease resistance in blue catfish. ConclusionsWe reported the first high-quality, chromosome-level assembly of the blue catfish genome, which provides the necessary genomic tool kit for transcriptome and methylome analysis, SNP discovery and marker-assisted selection, gene editing and genome engineering, and reproductive enhancement of the blue catfish and hybrid catfish. 

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4. A mitohormetic response to pro-oxidant exposure in the house mouse

   https://doi.org/10.1152/ajpregu.00176.2017  

   Zhang, Yufeng; Humes, Frances; Almond, Gregory; Kavazis, Andreas N.; Hood, Wendy R. (January 2018, American Journal of Physiology-Regulatory, Integrative and Comparative Physiology)

   Mitochondria are hypothesized to display a biphasic response to reactive oxygen species (ROS) exposure. In this study, we evaluated the time course changes in mitochondrial performance and oxidative stress in house mice following X-irradiation. Forty-eight mice were equally divided among six groups, including a nonirradiated control and five experimental groups that varied in time between X-ray exposure and euthanasia (1 h and 1, 4, 7, and 10 days after X-irradiation). We measured parameters associated with mitochondrial respiratory function and ROS emission from isolated liver and skeletal muscle mitochondria and levels of oxidative damage and antioxidants in liver, skeletal muscle, and heart tissues. Mitochondrial function dropped initially after X-irradiation but recovered quickly and was elevated 10 days after the exposure. Hydrogen peroxide production, lipid peroxidation, and protein carbonylation showed inverse U-shaped curves, with levels returning to control or lower than control, 10 days after X-irradiation. Enzymatic antioxidants and markers for mitochondrial biogenesis exhibited a tissue-specific response after irradiation. These data provide the first chronological description of the mitohormetic response after a mild dose of irradiation and highlight the protective response that cells display to ROS exposure. This study also provides valuable information and application for future mitochondrial and oxidative stress studies in numerous physiological settings. 

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5. Dynamic aqueous transformations of lithium cobalt oxide nanoparticle induce distinct oxidative stress responses of B. subtilis

   https://doi.org/10.1039/D0EN01151G  

   Gari, Metti K.; Lemke, Paul; Lu, Kelly H.; Laudadio, Elizabeth D.; Henke, Austin H.; Green, Curtis M.; Pho, Thomas; Hoang, Khoi Nguyen; Murphy, Catherine J.; Hamers, Robert J.; et al (January 2021, Environmental Science: Nano)

   null (Ed.)

   Lithium cobalt oxide (LiCoO 2 ), an example of nanoscale transition metal oxide and a widely commercialized cathode material in lithium ion batteries, has been shown to induce oxidative stress and generate intracellular reactive oxygen species (ROS) in model organisms. In this study, we aimed to understand the time-dependent roles of abiotic ROS generation and Co ions released in aqueous medium by LiCoO 2 NPs, and examined the induced biological responses in model bacterium, B. subtilis upon exposure. We found that the redox-active LiCoO 2 NPs produced abiotic ROS primarily through H 2 O 2 generation when freshly suspended. Subsequently, the freshly-suspended LiCoO 2 NPs induced additional DNA breakage, and changes in expression of oxidative stress genes in B. subtilis that could not be accounted for by the released Co ions alone. Notably, in 48 hour old LiCoO 2 suspensions, H 2 O 2 generation subsided while higher concentrations of Co ions were released. The biological responses in DNA damage and gene expression to the aged LiCoO 2 NPs recapitulated those induced by the released Co ions. Our results demonstrated oxidative stress mechanisms for bacteria exposed to LiCoO 2 NPs were mediated by the generation of distinct biotic and abiotic ROS species, which depended on the aqueous transformation state of the NPs. This study revealed the interdependent and dynamic nature of NP transformation and their biological consequences where the state of NPs resulted in distinct NP-specific mechanisms of oxidative injury. Our work highlights the need to capture the dynamic transformation of NPs that may activate the multiple routes of oxidative stress responses in cells. 

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