UMBC Marine-Estuarine-Environmental Sciences

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ANALYSIS OF SMYD1 FUNCTION AND THE MOLECULAR MECHANISM OF ACTION IN SKELETAL AND CARDIAC MUSCLE CELL DIFFENCIATION
(2024/01/01) Xu, Rui; Du, Shaojun; Zohar, Yonathan; Marine-Estuarine Environmental Sciences; Marine-Estuarine-Environmental Sciences
Smyd1, a key lysine methyltransferase, is crucial for myofibrillogenesis in both skeletal and cardiac muscles. The zebrafish orthologue, smyd1b, encodes two isoforms, Smyd1b_tv1 and Smyd1b_tv2, differing by 13 amino acids due to alternative splicing. It remains unclear whether the Smyd1b_tv1 and Smyd1b_tv2 isoforms exhibit distinct expression patterns and functions. The Janus face of Smyd1 in muscle cell development is perplexing and controversial. Some lines of evidence have suggested that Smyd1 functions as a chromatin modifier to regulate gene expression through a common post-translational mechanism. However, other lines of evidence indicate that Smyd1 may act as a chaperone protein in the cytosol to stabilize sarcomeric-associated proteins. The factors that trigger the enhanced protein degradation in muscles upon loss of Smyd1 function remain unknown. To determine whether Smyd1b_tv1 and Smyd1b_tv2 may have distinct function in muscle development, we first generated transgenic zebrafish models that express only Smyd1b_tv1 or Smyd1b_tv2 isoform in a zebrafish mutant that lacks the endogenous smyd1b gene. Functional analysis revealed that expression of Smyd1b_tv1 is essential for cardiomyocyte differentiation and fish viability, while Smyd1b_tv2 is dispensable for heart development and fish survival. Targeted deletion of Smyd1b_tv1 using CRISPR/Cas9 to produce smyd1b mutants that only express endogenous smyd1b_tv2, referred to as Smyd1bTV2. Surprisingly, Smyd1bTV2 fish were viable, and showed no apparent phenotypes. However, upon on the cardiac injury in adult fish, Smyd1bTV2 fish showed poor heart regeneration compared to WT siblings, emphasizing the critical role of Smyd1b_tv1 in cardiac regeneration. To elucidate the subcellular functionality of Smyd1b in orchestrating muscle development in zebrafish, multiple zebrafish transgenic lines expressing nuclear (Smyd1bNLS) and cytosolic (Smyd1bNES) Smyd1b were established. We showed that cytosolic Smyd1b (Smyd1bNES) completely complements Smyd1b-deficient mutants, while nuclear Smyd1b (Smyd1bNLS) exacerbates heart defects, highlighting the importance of Smyd1b cytosolic localization. Furthermore, comprehensive RNA-seq analysis revealed that smyd1b exhibits strikingly similar transcriptional profiles to unc45b, a chaperone mutant. In smyd1b-/- mutants, misfolded Myosin forms aggregate positive for ubiquitin during myogenesis, indicating Smyd1b primarily acts as a chaperone for Myosin folding, and the ubiquitin-proteasome system (UPS) may play an important role in deconstructing misfolded Myosin. Further investigation into specific UPS components, including CHIP and UBA1, showed that their loss did not ameliorate the sarcomeric defects or prevent sarcomeric protein from degradation in smyd1b-/- mutants. These findings imply the involvement of multiple E3 ligases in this process and the complexity of the protein quality control mechanisms in maintaining sarcomere integrity. Overall, Smyd1b primarily functions as a chaperone in the cytoplasm, aiding in myosin folding and sarcomere assembly. The degradation of misfolded myosin in smyd1b-/- mutants may be related to the ubiquitin-proteasome system (UPS). The two isoforms encoded by Smyd1b are not functionally equivalent, with Smyd1b_tv1 playing a more critical role in cardiac muscle development and regeneration.
Disease dynamics in marine keystone species: understanding Pacific oyster-Ostreid herpesvirus-1 and eelgrass-Labyrinthula spp. interactions
(2023-01-01) Agnew, M. Victoria; Schreier, Harold J.; Marine-Estuarine Environmental Sciences; Marine-Estuarine-Environmental Sciences
Keystone species are integral for the functioning of ecosystems and understanding threats to these species is incredibly important, especially in an era of global climate change. Marine environments are particularly vulnerable to changes in climate; specifically, marine disease is expected to increase, eliciting questions on how changes in disease dynamics may affect population structure of foundation species. A fundamental understanding of host-pathogen interactions is important to better predict potential changes over time. This dissertation is focused on two disease systems: the virus Ostreid Herpesvirus-1 (OsHV-1), which affects Pacific oysters Crassostrea gigas (Cg), and the protist Labyrinthula zosterae (Lz), which causes seagrass wasting disease (SWD) in Zostera marina (Zm). Although separate disease systems, the two host species often overlap in the intertidal zone and both have a substantial effect on the ecosystems they inhabit. SWD has been associated with losses of Zm globally, causing decreases in habitat, carbon sequestration, and sediment stabilization. Similarly, OsHV-1 causes mass mortality events in Cg globally, which has devastating impacts on oyster farms and the ecosystem services oysters provide. Answers to fundamental questions regarding host-pathogen interactions for both diseases are currently unknown. To address some of these questions, experiments were conducted to 1) determine virulence and sequence differences among Labyrinthula spp. via challenge studies and a partial 18S sequencing analysis; 2) test a mitigation strategy for SWD by co-culturing with Cg to assess the oystersÕ ability to filter the pathogen from the water; 3) determine if Cg stocks in the US are resistant to multiple OsHV-1 variants (termed microvariants or ÒµvarsÓ) via challenge experiments; and 4) investigate the viral shedding of tolerant and susceptible Cg exposed to multiple OsHVs-1 µvars. Pathogenic and non-pathogenic isolates of Labyrinthula spp. were isolated from Zm plants in the Pacific northwest, and differed based on partial 18S sequencing. In an infectious dose 50 experiment, only 6 Lz cells mL-1 were needed to cause SWD infection in 50% of exposed plants at both 15?C and 7.5?C. Co-culturing Cg with Zm exposed to Lz significantly decreased severity and intensity of SWD at both 11?C and 18?C. For OsHV-1, Cg lines accumulated high viral loads within their tissues, but had a range of tolerance to infection determined by a range in survival. Survival differed between spat and larger juveniles of the same family. Oysters exposed to a French µvar of OsHV-1 shed significantly higher amounts of virus than oysters exposed to a µvar from San Diego, CA. Overall, oysters shed the most virus from 24-120 hours post infection. These results provide crucial information about disease in two foundation species, Zm and Cg, and highlight the potential for these two species to benefit from one another. These findings provide information about marine disease systems of keystone species which will aid monitoring, management, and future research.
Understanding the mode of crustacean female sex hormone (CFSH) action in sex differentiation of the blue crab, Callinectes sapidus
(2023-01-01) Wang, Tao; Chung, Jum Sook; Marine-Estuarine Environmental Sciences; Marine-Estuarine-Environmental Sciences
Crustacean female sex hormone (CFSH), identified from the eyestalk of the female blue crab Callinectes sapidus, regulates developing adult-female-specific reproductive phenotypes of ovigerous setae for embryo brooding and gonopores for mating at the puberty-terminal molting. However, the mode of CFSH action is unknown in these adult-female-specific tissues. With earlier reports of vertebrate-type sex steroids present in some decapods, it is hypothesized that CFSH may exert its function in female sex differentiation via sex steroid hormones. On the other hand, male sex differentiation of decapod crustaceans is primarily regulated by the insulin-like androgenic gland factor (IAG). The expression of IAG induces masculinization, while RNA interference (RNAi)-mediated reduced IAG transcripts results in testicular degeneration and feminization. The inhibitory feedback between CFSH and IAG is supported by results obtained from RNAi studies and in vitro bioassay, but the inhibitory mechanism remains to be unveiled. This dissertation aimed to 1) clarify if the mode of CFSH action involves 17?-estradiol (E2) in females of the blue crab; 2) determine if males of the blue crab exhibit testosterone (T) and if the corresponding levels are related to IAG and CFSH transcripts; 3) identify the genes associated with ovigerous setae development using transcriptomic analysis. The significantly decreased E2 amounts and steroidogenic gene expressions in the adult-female-specific tissues following long-term CFSH knockdown suggest the potential involvement of E2 in the mode of CFSH action. The increase in T levels and IAG expression during male development and the opposite expression pattern between CFSH and IAG transcripts provide evidence for the presence of a putative regulatory interaction among IAG, CFSH, and T in decapods. Moreover, cuticle and tubulin transcripts, essential for developing ovigerous hairs located on ovigerous setae are identified, together with the genes involved in the wingless-type MMTV integration site family signaling and cell cycle pathways. These findings are formulated in a model, describing a putative mode of CFSH action in developing ovigerous setae, which may facilitate future research into decapod reproduction and sex differentiation.
Characterizing host-pathogen interactions between Zostera marina and Labyrinthula zosterae
(Frontiers, 2023-08-08) Venkataraman, Yaamini R.; Shore, Amanda; Dayal, Sukanya; Lee, James Sanghyun; Salimi, Mahsa Alidoost; Crandall, Grace; Loeher, Malina M.; Stoops, Mark; Swanger, Megan; Eisenlord, Morgan E.; Alstyne, Kathryn L. Van; Fast, Mark D.; Burge, Colleen; Groner, Maya L.
Introduction: Seagrass meadows serve as an integral component of coastal ecosystems but are declining rapidly due to numerous anthropogenic stressors including climate change. Eelgrass wasting disease, caused by opportunistic Labyrinthula spp., is an increasing concern with rising seawater temperature. To better understand the host-pathogen interaction, we paired whole organism physiological assays with dual transcriptomic analysis of the infected host and parasite. Methods: Eelgrass (Zostera marina) shoots were placed in one of two temperature treatments, 11° C or 18° C, acclimated for 10 days, and exposed to a waterborne inoculation containing infectious Labyrinthula zosterae (Lz) or sterile seawater. At two- and five-days post-exposure, pathogen load, visible disease signs, whole leaf phenolic content, and both host- and pathogen- transcriptomes were characterized. Results: Two days after exposure, more than 90% of plants had visible lesions and Lz DNA was detectable in 100% percent of sampled plants in the Lz exposed treatment. Concentrations of total phenolic compounds were lower after 5 days of combined exposure to warmer temperatures and Lz, but were unaffected in other treatments. Concentrations of condensed tannins were not affected by Lz or temperature, and did not change over time. Analysis of the eelgrass transcriptome revealed 540 differentially expressed genes in response to Lz exposure, but not temperature. Lz-exposed plants had gene expression patterns consistent with increased defense responses through altered regulation of phytohormone biosynthesis, stress response, and immune function pathways. Analysis of the pathogen transcriptome revealed up-regulation of genes potentially involved in breakdown of host defense, chemotaxis, phagocytosis, and metabolism. Discussion: The lack of a significant temperature signal was unexpected but suggests a more pronounced physiological response to Lz infection as compared to temperature. Pre-acclimation of eelgrass plants to the temperature treatments may have contributed to the limited physiological responses to temperature. Collectively, these data characterize a widespread physiological response to pathogen attack and demonstrate the value of paired transcriptomics to understand infections in a host-pathogen system.
World Society for Virology first international conference: Tackling global virus epidemics
(Elsevier, 2021-12-10) Söderlund-Venermo, Maria; Varma, Anupam; Guo, Deyin; Gladue, Douglas P.; Poole, Emma; Pujol, Flor H.; Pappu, Hanu; Romalde, Jesús L.; Kramer, Laura; Baz, Mariana; Venter, Marietjie; Moore, Matthew D.; Nevels, Michael M.; Ezzikouri, Sayeh; Vakharia, Vikram; Wilson, William C.; Malik, Yashpal S.; Shi, Zhengli; Abdel-Moneim, Ahmed S.
This communication summarizes the presentations given at the 1st international conference of the World Society for Virology (WSV) held virtually during 16–18 June 2021, under the theme of tackling global viral epidemics. The purpose of this biennial meeting is to foster international collaborations and address important viral epidemics in different hosts. The first day included two sessions exclusively on SARS-CoV-2 and COVID-19. The other two days included one plenary and three parallel sessions each. Last not least, 16 sessions covered 140 on-demand submitted talks. In total, 270 scientists from 49 countries attended the meeting, including 40 invited keynote speakers.
Road Salts as Environmental Constraints in Urban Pond Food Webs
(PLOS One, 2014-02-26) Meter, Robin J. Van; Swan, Christopher
Freshwater salinization is an emerging environmental filter in urban aquatic ecosystems that receive chloride road salt runoff from vast expanses of impervious surface cover. Our study was designed to evaluate the effects of chloride contamination on urban stormwater pond food webs through changes in zooplankton community composition as well as density and biomass of primary producers and consumers. From May – July 2009, we employed a 2×2×2 full-factorial design to manipulate chloride concentration (low = 177 mg L⁻¹ Cl⁻/high = 1067 mg L⁻¹ Cl⁻), gray treefrog (Hyla versicolor) tadpoles (presence/absence) and source of stormwater pond algae and zooplankton inoculum (low conductance/high conductance urban ponds) in 40, 600-L mesocosms. Road salt did serve as a constraint on zooplankton community structure, driving community divergence between the low and high chloride treatments. Phytoplankton biomass (chlorophyll [a] µg L⁻¹) in the mesocosms was significantly greater for the high conductance inoculum (P<0.001) and in the high chloride treatment (P = 0.046), whereas periphyton biomass was significantly lower in the high chloride treatment (P = 0.049). Gray treefrog tadpole time to metamorphosis did not vary significantly between treatments. However, mass at metamorphosis was greater among tadpoles that experienced a faster than average time to metamorphosis and exposure to high chloride concentrations (P = 0.039). Our results indicate differential susceptibility to chloride salts among algal resources and zooplankton taxa, and further suggest that road salts can act as a significant environmental constraint on urban stormwater pond communities.
Oyster gardening in the Baltimore Harbor: Quantifying oyster growth & influencing factors
(2023-01-01) Diaz, Jessica; Burns, Mercedes; Marine-Estuarine Environmental Sciences; Marine-Estuarine Environmental Sciences
In Baltimore, industrialization has degraded the ecosystem and displaced communities from the waterfront. Organizations like the Great Baltimore Oyster Partnership and the Environmental Justice Journalism Initiative aim to address these problems via restoration efforts. While oyster gardening has occurred in the Inner Harbor since 2013, the health and growth of the oysters has never been quantified, nor are any programs established in the Middle Branch. The goal of this study was to understand location-specific factors contributing to growth differences of the Eastern oyster (Crassostrea virginica). Oysters were deployed in the Harbor for 7 months and measurements for oyster growth and influencing factors collected. Oyster shell growth varied by site, but was not explained solely by temperature, salinity, and dissolved oxygen. Through phytoplankton metabarcoding, the preferred food sources of oysters were detected at all sites. These findings provide a baseline for quantifying oyster restoration initiatives in the Baltimore Harbor.
Seagrass Wasting Disease and the Causative Agent, Labyrinthula zosterae: Detection, Quantification, and Potential Mitigation
(2023-01-01) Bergman, Chelsea Noel; Schreier, Harold J; Marine-Estuarine Environmental Sciences; Marine-Estuarine Environmental Sciences
Eelgrass (Zostera marina) is an ecologically important seagrass providing numerous ecosystem services to coastal habitats globally. Z. marina is currently experiencing universal decline due to multiple factors, including degrading environmental conditions and disease. One disease commonly found in Z. marina beds is seagrass wasting disease (SWD) caused by the opportunistic pathogen Labyrinthula zosterae. SWD has previously caused mass die-offs of seagrass beds. Seagrass beds are well-surveyed in the Chesapeake Bay but SWD presence and prevalence remains unknown in the region. In this present study, seagrass beds were sampled in the Chesapeake Bay for SWD presence, lesion severity, and infection intensity. SWD and L. zosterae were present at four sites with one site having significantly higher disease severity and infection intensity. An undertested disease mitigation strategy is the use of farmed and naturally occurring oysters in wild populations, near eelgrass beds. The Pacific oyster, Crassostrea gigas, has been previously found to reduce and transmit SWD in Z. marina during laboratory trials. However, the density threshold of C. gigas needed to significantly reduce SWD is still unknown. Previous lab experiments also used higher doses of L. zosterae compared to recently determined environmentally relevant levels. Thus, understanding the impact of oyster densities on SWD at previously tested pathogen concentrations and more environmentally realistic concentrations is essential for a better understanding of the dynamics between disease, host, and a nonhost receptor. A mesocosm experiment was conducted with Z. marina co-cultured with two densities of oysters and exposed to two concentrations of pathogen, measuring their effect on blade growth, lesion severity, and infection intensity. High oyster density impeded growth while Z. marina growth benefited from low oyster densities. High pathogen concentrations increased SWD severity and L. zosterae infection intensity. High oyster densities significantly reduced the likelihood of L. zosterae infection presence. Results from this experiment confirmed that bivalves can reduce SWD under environmentally realistic pathogen concentrations and paves the way for integrated disease management. Further field testing is required to validate in-situ oyster filtration as a viable method for SWD mitigation.
Advancing Technology for Restoration: An investigation of the Solar Oysters Production System
(2023-01-01) Acker-Carter, Darryl Irving; Mendelson, Tamra; Marine-Estuarine Environmental Sciences; Marine-Estuarine Environmental Sciences
The Solar Oyster Production System (SOPS) was developed to expand growing capacity while decreasing the area required to grow oysters and reducing labor demands. SOPS is the first system in the world to grow oysters on continuously rotating ladders, however, little is known about the effect of consistent rotation on oyster growth. The goal of this study was to understand (1) the impact of rotation on growth of the Crassostrea virginica and (2) how the performance of oysters on SOPS compares to performance on traditional gardening methods. Oysters were deployed on rotational and static ladders on SOPS as well as oyster gardening cages provided by the Chesapeake Bay Foundation (CBF). The findings from this study reveal how consistent rotation affects shell shape and condition, and they provide baseline metrics for the further development of the technology.
Susceptibility of Shellfish Aquaculture Species in the Chesapeake Bay and Maryland Coastal Bays to the Ostreid Herpesvirus-1 Microvariants
(2022-01-01) Kachmar, Mariah Lynn; Schreier, Harold; Marine-Estuarine Environmental Sciences; Marine-Estuarine-Environmental Sciences
The Ostreid herpesvirus 1(OsHV-1) and its microvariants are highly virulent pathogens that cause mass mortalities of oysters and pose a threat to the shellfish aquaculture industry globally. OsHV-1 causes economically devastating mass mortality events up to 100% in the pacific oyster (Crassostrea gigas). However, OsHV-1 and its variants lack host specificity and are known to infect a range of bivalve species, such as bay scallops (Argopecten irradians), and be carried by the European green crab (Carcinus maenas). A recent laboratory study indicates that the eastern oyster (Crassostrea virginica) can experience infection and mortality from OsHV-1 which has significant implications for aquaculture species used in Maryland and globally, as eastern oysters have a wide geographic range spanning Northwest Atlantic to Panama and Venezuela. Therefore, determining the susceptibility of economically and ecologically important United States bivalve species to OsHV-1 is an essential step in improving biosecurity and disease management to protect the sustainability of the aquaculture industry. There is a lack of monitoring and research on OsHV-1 on the East coast of the United States, including in eastern oysters grown in the Chesapeake Bay, Virginia, and Maryland Coastal Bays where aquaculture is an important industry for food production, job security, and restoration efforts. Chesapeake and Maryland Coastal Bay species are already threatened by various parasitic and viral diseases, indicating that they may be vulnerable to OsHV-1. Surveys were conducted in June-August 2021 in the Maryland portion of the Chesapeake Bay to determine the prevalence and viral load of OsHV-1 at five aquaculture farms. Using quantitative PCR, OsHV-1 was not detected at any sites. However, continuous surveillance is crucial in mitigating possible introductions to the area. Experiments conducted at the University of Arizona examined the susceptibility and horizontal transmission of eastern oysters and hard clams. Importantly, it has been shown that OsHV-1 microvariants did not cause mortality or infection in eastern oysters and hard clams through natural infection pathways. However, eastern oysters, when injected with OsHV-1, can transmit the virus. This creates implications for same or similar species cultivated throughout the East Coast and Gulf of Mexico Coasts as well as transport of bivalves to the West Coast. Further experimentation using various family lines and establishment of surveillance programs is necessary to fully manage the spread and impact of OsHV-1 related disease.
Investigating interactions between climate, host life history and viral diversity across a trans-hemispheric range of marine ecosystems
(2022-01-01) Zhao, Mingli; Schott, Eric; Schreier, Harold; Marine-Estuarine Environmental Sciences; Marine-Estuarine-Environmental Sciences
Marine infectious diseases and pathogens substantially impact the structure and function of marine communities by causing mortalities and altering host behaviors. The interactions between host and pathogen, determining the epidemiologicaloutcomes are affected by many factors including climate, host life history, and human activities. Studies on marine disease epidemiology and ecology, including both natural and anthropogenic transmission pathways, are necessary for better understanding how these factors potentially influence the host-pathogen interactions. A significant proportion of marine pathogens are viruses; they cause severe infectious diseases and mortalities in many marine organisms, including crustaceans. Virus-related diseases and mortalities have been identified and reported in the Atlantic blue crab, Callinectes sapidus, for more than half a century. With a wide geographic distribution across both hemispheres and a temperature-dependent variable life history, blue crab and its pathogenic viruses constitute a well-suited pathosystem for investigating the potential influences of climate, seasonality, and host life history on viral disease emergence and spread in marine ecosystems. This dissertations applied the "blue crab-virus” pathosystem, to investigate factors that potentially influence the interactions between blue crab and its viral symbionts. The studies mainly focused on three objectives: 1) Investigate the influences of climate, seasonality, and host life history on the prevalence and disease ecology of a virus that is pathogenic to blue crab. 2) Assess the influences of climate, seasonality, and host life history on viral genetic diversity and genetic structures across a wide spatial and temporal range. 3) Characterize genome sequences and biological characteristics of newly identified viruses in blue crabs. The studies encompassed in this dissertations demonstrate, in a single host species, that climate, temperature, and host life history traits drive patterns of virus species diversity and genetic variation across the entire range of the host. One significant revelation was the evidence of long-distance movement of virus pathogen genotypes by human transport of infected blue crabs between states in the United States. The dissertations concludes with a discussion of the potential for next-generation sequencing to discover and study the movement of known and newly discovered viruses in marine hosts.
Developing technologies to produce reproductively sterile finfish and oysters, and characterizing changes of gene expression in the pituitary of sterile fish by single-cell RNA sequencing
(2022-01-01) Xu, Lan; Wong, Ten-Tsao; Zohar, Yonathan; Marine-Estuarine Environmental Sciences; Marine-Estuarine-Environmental Sciences
Aquaculture is the fastest-growing food sector and is viewed as a long-term sustainable approach to meet the rising global demand for seafood. During the expansion and advancement of aquaculture, minimizing ecological impacts should be pursued concomitantly with maximizing production. Undesired maturation and reproduction are major challenges in aquaculture in terms of genetic introgression, precocious maturation, and reproduction-related mortality, which can have profound ecological and economic impacts. Farming reproductively sterile animals effectively mitigate these challenges and promote environmentally and economically sustainable aquaculture practices. We have developed a novel immersion-based gene-silencing sterilization technology in zebrafish, which has enormous application potential for aquaculture. This dissertations aimed to 1) transfer the novel technology and apply it to aquaculture species, using salmonids and oysters as the models, and evaluate their gonadal development; 2) advance this technology in a traceable manner using fluorescence-labeled Morpholino; 3) investigate the changes of gene expression in the pituitary of sterile fish by single-cell RNA sequencing. The successful production of sterile salmonids achieved in this study demonstrated a proof of principle for this new sterilization technology, facilitating future transfer and application to other commercially important finfish aquaculture species. The delivery of traceable fluorescence-labeled Morpholinos represented a strategy that can accelerate the development and optimization of this technology in both finfish and oysters. Comparing gene expression in the pituitaries between fertile and sterile female fishes provided new insights into pituitary responses to the absence of ovary development at a single-cell resolution. The development and advancement of sterilization technologies in this study would facilitate farming sterile populations, promote cost-effective and ecologically responsible aquaculture practices, and serve as a model for expanding sustainable aquaculture globally.
Molecular mechanisms regulating reproduction in the presence and absence of the hypophysiotropic GnRH in zebrafish females
(2022-01-01) Tanaka, Sakura; Yonathan, Zohar ZY; Marine-Estuarine Environmental Sciences; Marine-Estuarine-Environmental Sciences
Gonadotropin-releasing hormone (GnRH) is an essential neuropeptide for inducing the luteinizing hormone (LH) secretion in vertebrates. Most vertebrates possess two or three GnRH isoforms, and GnRH1 is known as a regulator of reproduction, especially the LH secretion. The zebrafish lost GnRH1 during evolution, and another GnRH, GnRH3, is considered to function similarly to GnRH1 in regulating the LH secretion. However, previous studies exhibited that the GnRH3 knockout does not affect fertility in zebrafish. This finding may be explained by functional compensation or redundancy that mitigates the absence of GnRH3. The present study depicts evidence supporting the functional redundancy theory and pointing to GnRH3 dispensability in modulating the LH secretion in zebrafish. To determine the role of the GnRH3 and its neurons in controlling ovulation in zebrafish, conditional GnRH3 neuronal ablation in adult fish was performed, which, however, resulted in no effects on fertility. Next, to examine whether other neuropeptides can regulate LH secretion, this study demonstrated that another neuropeptide, vasoactive intestinal peptide (Vip), induces LH secretion in zebrafish. Intracerebroventricular administration of Vip augmented plasma LH levels in wild-type (WT) and gnrh3�/� females, with no changes in pituitary GnRH3 content. These findings indicate that Vip induces LH release, by acting with or through a non-GnRH3 factor(s). Finally, to determine whether the absence of GnRH3 affects pituitary states, and to identify potential factors pertinent to the LH secretion, expression profiles of individual pituitary cells of WT and gnrh3�/� female zebrafish were analyzed by single-cell transcriptomics. In LH gonadotropes, there were no differences in LH secretion-related gene expressions between the genotypes, but some non-reproductive hormone gene expression was increased in gnrh3�/�. A potential novel cell type was also classified in WT, which was barely detectable in gnrh3�/�. These changes suggest that GnRH3 suppresses the expression of certain genes that contribute to the pituitary cell specialization. Taken altogether, GnRH3 may not work solely as critical factors in inducing the LH secretion in zebrafish, which is likely stimulated through functional redundancy. The present study provides novel evidence that supports the concept of a GnRH-independent system in vertebrate reproduction.
Effects of Infectious Diseases on Population Dynamics of Marine Organisms in Chesapeake Bay
(Springer Nature, 2021-03-24) Jesse, Jerelle A.; Agnew, M. Victoria; Arai, Kohma; Armstrong, C. Taylor; Hood, Shannon M.; Kachmar, Mariah L.; Long, Jessie T.; McCarty, Alexandra J.; Ross, Morgan O.; Rubalcava, Kasondra D.; Shaner, Jacob; Tanaka, Sakura; Wood, Lindsay; Schott, Eric J.; Wilberg, Michael J.
Diseases are important drivers of population and ecosystem dynamics. This review synthesizes the effects of infectious diseases on the population dynamics of nine species of marine organisms in the Chesapeake Bay. Diseases generally caused increases in mortality and decreases in growth and reproduction. Effects of diseases on eastern oyster (Crassostrea virginica) appear to be low in the 2000s compared to effects in the 1980s–1990s. However, the effects of disease were not well monitored for most of the diseases in marine organisms of the Chesapeake Bay, and few studies considered effects on growth and reproduction. Climate change and other anthropogenic effects are expected to alter host-pathogen dynamics, with diseases of some species expected to worsen under predicted future conditions (e.g., increased temperature). Additional study of disease prevalence, drivers of disease, and effects on population dynamics could improve fisheries management and forecasting of climate change effects on marine organisms in the Chesapeake Bay.
Dichotomy between regulation of coral bacterial communities and calcification physiology under ocean acidification conditions
(American Society for Microbiology) Shore, A.; Day, R. D.; Stewart, J. A.; Burge, C.A.
Ocean acidification (OA) threatens the growth and function of coral reef ecosystems. A key component to coral health is the microbiome, but little is known about the impact of OA on coral microbiomes. A submarine CO2 vent at Maug Island in the Northern Marianas Islands provides a natural pH gradient to investigate coral responses to long-term OA conditions. Three coral species (Pocillopora eydouxi, Porites lobata, and Porites rus) were sampled from three sites where mean seawater pH is 8.04, 7.98, and 7.94. We characterized coral bacterial communities (using 16S rRNA gene sequencing) and determined pH of the extracellular calcifying fluid (ECF) (using skeletal boron isotopes) across the seawater pH gradient. Bacterial communities of both Porites species stabilized (decreases in community dispersion) with decreased seawater pH, coupled with large increases in the abundance of Endozoicomonas, an endosymbiont. P. lobata experienced a significant decrease in ECF pH near the vent, whereas P. rus experienced a trending decrease in ECF pH near the vent. By contrast, Pocillopora exhibited bacterial community destabilization (increases in community dispersion), with significant decreases in Endozoicomonas abundance, while its ECF pH remained unchanged across the pH gradient. Our study shows that OA has multiple consequences on Endozoicomonas abundance and suggests that Endozoicomonas abundance may be an indicator of coral response to OA. We reveal an interesting dichotomy between two facets of coral physiology (regulation of bacterial communities and regulation of calcification), highlighting the importance of multidisciplinary approaches to understanding coral health and function in a changing ocean.
The Roles of Gonadotropin-releasing Hormone 2 (Gnrh2) in Feeding and Reproduction in Zebrafish: A Potential Mediator of These Interlinked Processes
(2019-01-01) Marvel, Miranda; Zohar, Yonathan; Marine-Estuarine Environmental Sciences; Marine-Estuarine-Environmental Sciences
Gonadotropin-releasing hormone (GNRH) is the neuropeptide in vertebrates most well-known for controlling reproduction and stimulating the gonadotropins, luteinizing hormone (LH) and follicle-stimulating hormone (FSH), from the pituitary. The gonadotropins circulate to the gonads and stimulate steroidogenesis and gametogenesis. There are three forms of GNRH, named for their location and function in the brain. GNRH1 is known to be the main hypophysiotropic isoform regulating gonadotropin release. GNRH2 is found in the midbrain and, despite being the most evolutionarily conserved and ubiquitous, is the least studied form among the three, most likely due to the absence of GNRH2 protein in common murine research models. Zebrafish, another common vertebrate model for genetic manipulation and biological studies, possesses Gnrh2 and is therefore an ideal organism to study this neuropeptide. Through a combination of gene knockout/knockdown, neuroanatomical imaging, and functional assays, the roles of Gnrh2 in zebrafish were comprehensively explored. Gnrh2 knockout (gnrh2-/-) zebrafish demonstrated decreased lhb expression, compromised oocyte quality, increased feeding and growth, and, most strikingly, major inhibition of spawning and oocyte maturation after long-term fasting. Neuroanatomical assays confirmed that Gnrh2 projected more neurons to gonadotropes under fasting conditions, whereas Gnrh3 was inhibited. Interestingly, Gnrh2 was unable to compensate for Gnrh3 loss, as double knockout (gnrh2-/-;gnrh3-/-) zebrafish displayed normal reproduction. Through transcriptomics and qPCR, novel differentially expressed reproductive factors were discovered in knockout zebrafish, with potential reproductive regulatory roles. Additionally, examination of Gnrh2 neuronal projections identified fibers innervating melatonin cells, neurons of the feeding factor, Agouti-related peptide 1 (Agrp1), and neurons of the reproduction regulator, Gonadotropin-inhibitory hormone (Gnih). Gnrh2 was also able to modulate gnih and agrp1 expression. Additionally, a previously unstudied population of Gnrh2 was identified in the olfactory region and multiple experiments implicated these neurons in transducing pheromonal cues, and thus affecting reproductive behavior. Overall, Gnrh2 most likely has roles in stimulating lhb expression, maintaining oocyte quality, transducing pheromonal cues, and reducing feeding behavior through the modulation of agrp1 and potentially melatonin. Under fasting conditions, Gnrh2 exhibits plasticity to become the main hypophysiotropic stimulator of gonadotropin secretion. Gnrh2 therefore appears to be an important upstream factor mediating feeding and reproductive processes in vertebrates.
Enhanced Enrichment of Medaka Ovarian Germline Stem Cells by a Combination of Density Gradient Centrifugation and Differential Plating
(MDPI, 2020-10-24) Ryu, Jun Hyung; Gong, Seung Pyo
Fish ovarian germline stem cells (OGSCs) have great potential in various biological fields due to their ability to generate large numbers of mature eggs. Therefore, selective enrichment of OGSCs is a prerequisite for successful applications. To determine the optimal conditions for the enrichment of OGSCs from Japanese medaka (Oryzias latipes), we evaluated the effects of Percoll density gradient centrifugation (PDGC), differential plating (DP), and a combination of both methods. Based on cell morphology and gene expression of germ cell-specific Vasa and OGSC-specific Nanos2, we demonstrated that of seven density fractions obtained following PDGC, the 30–35% density fraction contained the highest proportion of OGSCs, and that Matrigel was the most effective biomolecule for the enrichment of Oryzias latipes OGSCs by DP in comparison to laminin, fibronectin, gelatin, and poly-l-lysine. Furthermore, we confirmed that PDGC and DP in combination significantly enhanced the efficiency of OGSC enrichment. The enriched cells were able to localize in the gonadal region at a higher efficiency compared to non-enriched ovarian cells when transplanted into the developing larvae. Our approach provides an efficient way to enrich OGSCs without using OGSC-specific surface markers or transgenic strains expressing OGSC-specific reporter proteins.
ICTV virus taxonomy profile: Picobirnaviridae
(Microbiiology Society, 2018-11-28) Delmas, Bernard; Attoui, Houssam; Ghosh, Souvik; Malik, Yashpal S.; Mundt, Egbert; Vakharia, Vikram N.; ICTV Report Consortium
Picobirnaviridae is a family of viruses with bi-segmented (rarely unsegmented) dsRNA genomes comprising about 4.4 kbp in total, with small, non-enveloped spherical virions. The family includes one genus (Picobirnavirus) grouping three genetic clusters with high sequence variability, two defined by viruses infecting vertebrates and a third with viruses found in invertebrates. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the taxonomy of Picobirnaviridae

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