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Sirovy KA, Casas SM, La Peyre JF, Kelly MW. Population-specific responses in eastern oysters exposed to low salinity in the northern Gulf of Mexico. J Exp Biol 2023:jeb.244315. [PMID: 37350275 DOI: 10.1242/jeb.244315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Accepted: 06/08/2023] [Indexed: 06/24/2023]
Abstract
Eastern oysters, Crassostrea virginica, are facing rapid environmental changes in the northern Gulf of Mexico and can respond to these changes via plasticity or evolution. Plastic responses can immediately buffer against environmental changes, although this buffering may impact the organism's ability to evolve in subsequent generations. While plasticity and evolution are not mutually exclusive, the relative contribution and interaction between them remain unclear. In this study, we investigate the roles of plastic and evolved responses of C. virginica acclimated to low salinity using a common garden experiment with four populations exposed to two salinities. We use three transcriptomic analyses (edgeR, PERMANOVA, and WGCNA) combined with physiology data to identify the effect of genotype (population), environment (salinity), and genotype-by-environment interaction on both whole organism and molecular phenotypes. We demonstrate that variation in gene expression is mainly driven by population, with relatively small changes in response to salinity. In contrast, the morphology and physiology data reveal that salinity has a larger influence on oyster performance than the population of origin. All analyses lacked signatures of genotype-by-environment interaction, and in contrast to previous studies, we find no evidence for population-specific responses to low salinity. However, individuals from the highest salinity estuary displayed highly divergent gene expression from other populations, which could potentially drive population-specific responses to other stressors. Our findings suggest that C. virginica largely rely on plasticity in physiology to buffer the effects of low salinity, but that these changes in physiology do not rely on large persistent changes in gene expression.
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Affiliation(s)
- Kyle A Sirovy
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA, 70803, USA
| | - Sandra M Casas
- School of Animal Sciences, Louisiana State University Agricultural Center, Baton Rouge, LA, 70803, USA
| | - Jerome F La Peyre
- School of Animal Sciences, Louisiana State University Agricultural Center, Baton Rouge, LA, 70803, USA
| | - Morgan W Kelly
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA, 70803, USA
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Bodenstein S, Casas SM, Tiersch TR, Peyre JFL. Energetic budget of diploid and triploid eastern oysters during a summer die-off. Front Mar Sci 2023; 10:1194296. [PMID: 38577631 PMCID: PMC10993659 DOI: 10.3389/fmars.2023.1194296] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 04/06/2024]
Abstract
Triploid oysters are widely used in off-bottom aquaculture of eastern oysters, Crassostrea virginica. However, farmers of the Gulf of Mexico (GoM) and Atlantic coast estuaries have observed unresolved, late-spring die-offs of triploid oysters, threatening the sustainability of triploid aquaculture. To investigate this, the physiological processes underlying oyster growth (e.g., feeding, respiration) and mortality of one-year-old diploid and triploid oysters were compared in early summer following an uptick in mortality. It was predicted that higher triploid mortality was the result of energetic imbalances (increased metabolic demands and decreased feeding behavior). Oyster clearance rates, percentage of time valves were open, absorption efficiency, oxygen consumption rates (basal and routine), ammonia excretion rate were measured in the laboratory and scope for growth was calculated. In addition, their condition index, gametogenic stage, Perkinsus marinus infection level, and mortality were measured. Mortality of triploids in the laboratory was greater than for diploids, mirroring mortality observed in a related field study. The physiological parameters measured, however, could not explain triploid mortality. Scope for growth, condition index, and clearance rates of triploids were greater than for diploids, suggesting sufficient energy reserves, while all other measurements where similar between the ploidies. It remains to be determined whether mortality could be caused from disruption of energy homeostasis at the cellular level.
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Affiliation(s)
- Sarah Bodenstein
- Aquatic Germplasm and Genetic Resources Center, School of Renewable Natural Resources, Louisiana State University Agricultural Center, Baton Rouge, LA, United States
| | - Sandra M. Casas
- School of Animal Sciences, Louisiana State University Agricultural Center, Baton Rouge, LA, United States
| | - Terrence R. Tiersch
- Aquatic Germplasm and Genetic Resources Center, School of Renewable Natural Resources, Louisiana State University Agricultural Center, Baton Rouge, LA, United States
| | - Jerome F. La Peyre
- School of Animal Sciences, Louisiana State University Agricultural Center, Baton Rouge, LA, United States
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Bodenstein S, Callam BR, Walton WC, Rikard FS, Tiersch TR, La Peyre JF. Survival and growth of triploid eastern oysters, Crassostrea virginica, produced from wild diploids collected from low-salinity areas. Aquaculture 2023; 564:739032. [PMID: 36778722 PMCID: PMC9910191 DOI: 10.1016/j.aquaculture.2022.739032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Triploid Eastern oysters have been reported to suffer greater mortalities than diploids when exposed to low-salinity (<5) conditions in the U.S. Gulf of Mexico and Atlantic estuaries. As such, the effect of broodstock parentage was investigated on the low-salinity tolerance of triploid progeny produced by mating diploid females (collected from three Louisiana estuaries differing in salinity regimes) with male tetraploids at two hatcheries. Diploid crosses were also produced using the wild broodstocks to verify expected differences in low-salinity tolerance among diploid progeny and between ploidy levels. All progeny were deployed at low and moderate-salinity (averages of 9.3 and 19.4) field sites to monitor monthly growth and mortality. Sex ratio, gametogenic stage, gonad-to-body ratio, condition index, and Perkinsus marinus infection were also measured periodically at both field sites Although high triploid mortality at the low-salinity site prevented complete analysis, results indicated that diploid parentage had little effect on triploid survival at low salinity. Broodstock parentage affected diploid mortality and growth, although results did not match with predictions made based on historical salinity at broodstock collection sites. Ploidy level had the largest effect on triploid survival and growth followed by the hatchery site where the oysters were produced.
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Affiliation(s)
- Sarah Bodenstein
- Aquatic Germplasm and Genetic Resources Center, School of Renewable Natural Resources, Louisiana State University Agricultural Center, Baton Rouge, LA 70820, United States of America
| | - Brian R. Callam
- Louisiana State University and Louisiana Sea Grant Outreach Program, Baton Rouge, LA 70803, United States of America
| | - William C. Walton
- Department of Fisheries Science, Virginia Institute of Marine Science, Gloucester Point, VA 23062, United States of America
| | - F. Scott Rikard
- Auburn University Shellfish Laboratory, School of Fisheries, Aquaculture, and Aquatic Sciences, Auburn University, Dauphin Island, AL 36528, United States of America
| | - Terrence R. Tiersch
- Aquatic Germplasm and Genetic Resources Center, School of Renewable Natural Resources, Louisiana State University Agricultural Center, Baton Rouge, LA 70820, United States of America
| | - Jerome F. La Peyre
- School of Animal Sciences, Louisiana State University Agricultural Center, Baton Rouge, LA 70803, United States of America
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Marshall DA, Coxe NC, La Peyre MK, Walton WC, Rikard FS, Pollack JB, Kelly MW, La Peyre JF. Tolerance of northern Gulf of Mexico eastern oysters to chronic warming at extreme salinities. J Therm Biol 2021; 100:103072. [PMID: 34503809 DOI: 10.1016/j.jtherbio.2021.103072] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Revised: 07/13/2021] [Accepted: 08/03/2021] [Indexed: 11/28/2022]
Abstract
The eastern oyster, Crassostrea virginica, provides critical ecosystem services and supports valuable fishery and aquaculture industries in northern Gulf of Mexico (nGoM) subtropical estuaries where it is grown subtidally. Its upper critical thermal limit is not well defined, especially when combined with extreme salinities. The cumulative mortalities of the progenies of wild C. virginica from four nGoM estuaries differing in mean annual salinity, acclimated to low (4.0), moderate (20.0), and high (36.0) salinities at 28.9 °C (84 °F) and exposed to increasing target temperatures of 33.3 °C (92 °F), 35.6 °C (96 °F) or 37.8 °C (100 °F), were measured over a three-week period. Oysters of all stocks were the most sensitive to increasing temperatures at low salinity, dying quicker (i.e., lower median lethal time, LT50) than at the moderate and high salinities and resulting in high cumulative mortalities at all target temperatures. Oysters of all stocks at moderate salinity died the slowest with high cumulative mortalities only at the two highest temperatures. The F1 oysters from the more southern and hypersaline Upper Laguna Madre estuary were generally more tolerant to prolonged higher temperatures (higher LT50) than stocks originating from lower salinity estuaries, most notably at the highest salinity. Using the measured temperatures oysters were exposed to, 3-day median lethal Celsius degrees (LD50) were estimated for each stock at each salinity. The lowest 3-day LD50 (35.1-36.0 °C) for all stocks was calculated at a salinity of 4.0, while the highest 3-day LD50 (40.1-44.0 °C) was calculated at a salinity of 20.0.
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Affiliation(s)
- Danielle A Marshall
- School of Renewable Natural Resources, Louisiana State University Agricultural Center, Baton Rouge, LA, 70803, USA
| | - Nicholas C Coxe
- School of Renewable Natural Resources, Louisiana State University Agricultural Center, Baton Rouge, LA, 70803, USA
| | - Megan K La Peyre
- U.S. Geological Survey, Louisiana Fish and Wildlife Cooperative Research Unit, School of Renewable Natural Resources, Louisiana State University Agricultural Center, Baton Rouge, LA, 70803, USA
| | - William C Walton
- School of Fisheries, Aquaculture, and Aquatic Sciences, Auburn University, Dauphin Island, AL, 36528, USA
| | - F Scott Rikard
- School of Fisheries, Aquaculture, and Aquatic Sciences, Auburn University, Dauphin Island, AL, 36528, USA
| | - Jennifer Beseres Pollack
- Harte Research Institute for Gulf of Mexico Studies, Texas A&M University Corpus Christi, Texas, 78412, USA
| | - Morgan W Kelly
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA, 70803, USA
| | - Jerome F La Peyre
- School of Animal Sciences, Louisiana State University Agricultural Center, Baton Rouge, LA, 70803, USA.
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Sirovy KA, Johnson KM, Casas SM, La Peyre JF, Kelly MW. Lack of genotype-by-environment interaction suggests limited potential for evolutionary changes in plasticity in the eastern oyster, Crassostrea virginica. Mol Ecol 2021; 30:5721-5734. [PMID: 34462983 DOI: 10.1111/mec.16156] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Revised: 08/18/2021] [Accepted: 08/23/2021] [Indexed: 12/13/2022]
Abstract
Eastern oysters in the northern Gulf of Mexico are facing rapid environmental changes and can respond to this change via plasticity or evolution. Plasticity can act as an immediate buffer against environmental change, but this buffering could impact the organism's ability to evolve in subsequent generations. While plasticity and evolution are not mutually exclusive, the relative contribution and interaction between them remains unclear. In this study, we investigate the roles of plastic and evolved responses to environmental variation and Perkinsus marinus infection in Crassostrea virginica by using a common garden experiment with 80 oysters from six families outplanted at two field sites naturally differing in salinity. We use growth data, P. marinus infection intensities, 3' RNA sequencing (TagSeq) and low-coverage whole-genome sequencing to identify the effect of genotype, environment and genotype-by-environment interaction on the oyster's response to site. As one of first studies to characterize the joint effects of genotype and environment on transcriptomic and morphological profiles in a natural setting, we demonstrate that C. virginica has a highly plastic response to environment and that this response is parallel among genotypes. We also find that genes responding to genotype have distinct and opposing profiles compared to genes responding to environment with regard to expression levels, Ka/Ks ratios and nucleotide diversity. Our findings suggest that C. virginica may be able to buffer the immediate impacts of future environmental changes by altering gene expression and physiology, but the lack of genetic variation in plasticity suggests limited capacity for evolved responses.
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Affiliation(s)
- Kyle A Sirovy
- Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana, USA
| | - Kevin M Johnson
- Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana, USA
| | - Sandra M Casas
- School of Animal Sciences, Louisiana State University Agricultural Center, Baton Rouge, Louisiana, USA
| | - Jerome F La Peyre
- School of Animal Sciences, Louisiana State University Agricultural Center, Baton Rouge, Louisiana, USA
| | - Morgan W Kelly
- Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana, USA
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Johnson KM, Jones HR, Casas SM, La Peyre JF, Kelly MW. Transcriptomic signatures of temperature adaptation in the eastern oyster Crassostrea virginica. J Evol Biol 2021; 34:1212-1224. [PMID: 33837581 DOI: 10.1111/jeb.13789] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2020] [Revised: 02/09/2021] [Accepted: 03/18/2021] [Indexed: 12/20/2022]
Abstract
The large geographic distribution of the eastern oyster, Crassostrea virginica, makes it an ideal species to test how populations have adapted to latitudinal gradients in temperature. Despite inhabiting distinct thermal regimes, populations of C. virginica near the species' southern and northern geographic range show no population differences in their physiological response to temperature. In this study, we used comparative transcriptomics to understand how oysters from either end of the species' range maintain enantiostasis across three acclimation temperatures (10, 20, and 30°C). With this approach, we identified genes that were differentially expressed in response to temperature between individuals of C. virginica collected from New Brunswick, Canada and Louisiana, USA. We observed a core set of genes whose expression responded to temperature in both populations, but also an even larger set of genes with expression patterns that were unique to each population. Intriguingly, the genes with population-specific responses to temperature had elevated FST and Ka/Ks ratios compared to the genome-wide average. In contrast, genes showing only a response to temperature were found to only have elevated FST values suggesting that divergent FST may be due to selection on linked regulatory regions rather than positive selection on protein coding regions. Taken together, our results suggest that, despite coarse-scale physiological similarities, natural selection has shaped divergent gene expression responses to temperature in geographically separated populations of this broadly eurythermal marine invertebrate.
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Affiliation(s)
- Kevin M Johnson
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA, USA.,Center for Coastal Marine Sciences, California Polytechnic State University, San Luis Obispo, CA, USA.,California Sea Grant, University of California San Diego, La Jolla, CA, USA
| | - Hollis R Jones
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA, USA.,Department of Animal Science, University of California, Davis, CA, USA
| | - Sandra M Casas
- School of Animal Sciences, Louisiana State University Ag Center, Baton Rouge, LA, USA
| | - Jerome F La Peyre
- School of Animal Sciences, Louisiana State University Ag Center, Baton Rouge, LA, USA
| | - Morgan W Kelly
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA, USA
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7
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Griffiths JS, Johnson KM, Sirovy KA, Yeats MS, Pan FTC, La Peyre JF, Kelly MW. Transgenerational plasticity and the capacity to adapt to low salinity in the eastern oyster, Crassostrea virginica. Proc Biol Sci 2021; 288:20203118. [PMID: 34004136 PMCID: PMC8131124 DOI: 10.1098/rspb.2020.3118] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2020] [Accepted: 04/29/2021] [Indexed: 12/11/2022] Open
Abstract
Salinity conditions in oyster breeding grounds in the Gulf of Mexico are expected to drastically change due to increased precipitation from climate change and anthropogenic changes to local hydrology. We determined the capacity of the eastern oyster, Crassostrea virginica, to adapt via standing genetic variation or acclimate through transgenerational plasticity (TGP). We outplanted oysters to either a low- or medium-salinity site in Louisiana for 2 years. We then crossed adult parents using a North Carolina II breeding design, and measured body size and survival of larvae 5 dpf raised under low or ambient salinity. We found that TGP is unlikely to significantly contribute to low-salinity tolerance since we did not observe increased growth or survival in offspring reared in low salinity when their parents were also acclimated at a low-salinity site. However, we detected genetic variation for body size, with an estimated heritability of 0.68 ± 0.25 (95% CI). This suggests there is ample genetic variation for this trait to evolve, and that evolutionary adaptation is a possible mechanism through which oysters will persist with future declines in salinity. The results of this experiment provide valuable insights into successfully breeding low-salinity tolerance in this commercially important species.
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Affiliation(s)
- Joanna S. Griffiths
- Department of Environmental Toxicology and Department of Wildlife, Fish, and Conservation Biology, University of California, 4121 Meyer Hall, Davis, CA 95616, USA
| | - Kevin M. Johnson
- Biological Sciences Department, California Polytechnic State University, San Luis Obispo, CA, USA
| | - Kyle A. Sirovy
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA, USA
| | - Mark S. Yeats
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA, USA
| | - Francis T. C. Pan
- Department of Biological Sciences, University of Southern California, Los Angeles, CA, USA
| | - Jerome F. La Peyre
- Department of Veterinary Science, Louisiana State University, Baton Rouge, LA, USA
| | - Morgan W. Kelly
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA, USA
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Marshall DA, Casas SM, Walton WC, Rikard FS, Palmer TA, Breaux N, La Peyre MK, Beseres Pollack J, Kelly M, La Peyre JF. Divergence in salinity tolerance of northern Gulf of Mexico eastern oysters under field and laboratory exposure. Conserv Physiol 2021; 9:coab065. [PMID: 34447578 PMCID: PMC8384081 DOI: 10.1093/conphys/coab065] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/2020] [Revised: 03/30/2021] [Accepted: 08/18/2021] [Indexed: 05/04/2023]
Abstract
The eastern oyster, Crassostrea virginica, is a foundation species within US Gulf of Mexico (GoM) estuaries that has experienced substantial population declines. As changes from management and climate are expected to continue to impact estuarine salinity, understanding how local oyster populations might respond and identifying populations with adaptations to more extreme changes in salinity could inform resource management, including restoration and aquaculture programs. Wild oysters were collected from four estuarine sites from Texas [Packery Channel (PC): 35.5, annual mean salinity, Aransas Bay (AB): 23.0] and Louisiana [Calcasieu Lake (CL): 16.2, Vermilion Bay (VB): 7.4] and spawned. The progeny were compared in field and laboratory studies under different salinity regimes. For the field study, F1 oysters were deployed at low (6.4) and intermediate (16.5) salinity sites in Alabama. Growth and mortality were measured monthly. Condition index and Perkinsus marinus infection intensity were measured quarterly. For the laboratory studies, mortality was recorded in F1 oysters that were exposed to salinities of 2.0, 4.0, 20.0/22.0, 38.0 and 44.0 with and without acclimation. The results of the field study and laboratory study with acclimation indicated that PC oysters are adapted to high-salinity conditions and do not tolerate very low salinities. The AB stock had the highest plasticity as it performed as well as the PC stock at high salinities and as well as Louisiana stocks at the lowest salinity. Louisiana stocks did not perform as well as the Texas stocks at high salinities. Results from the laboratory studies without salinity acclimation showed that all F1 stocks experiencing rapid mortality at low salinities when 3-month oysters collected at a salinity of 24 were used and at both low and high salinities when 7-month oysters collected at a salinity of 14.5 were used.
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Affiliation(s)
- Danielle A Marshall
- School of Renewable Natural Resources, Louisiana State University Agricultural Center, Baton Rouge, LA 70803, USA
| | - Sandra M Casas
- School of Animal Sciences, Louisiana State University Agricultural Center, Baton Rouge, LA 70803, USA
| | - William C Walton
- School of Fisheries, Aquaculture, and Aquatic Sciences, Auburn University, Dauphin Island, AL 36528, USA
| | - F Scott Rikard
- School of Fisheries, Aquaculture, and Aquatic Sciences, Auburn University, Dauphin Island, AL 36528, USA
| | - Terence A Palmer
- Harte Research Institute for Gulf of Mexico Studies, Texas A&M University-Corpus Christi, TX, 78412, USA
| | - Natasha Breaux
- Harte Research Institute for Gulf of Mexico Studies, Texas A&M University-Corpus Christi, TX, 78412, USA
| | - Megan K La Peyre
- US Geological Survey, Louisiana Fish and Wildlife Cooperative Research Unit, School of Renewable Natural Resources, Louisiana State University Agricultural Center, Baton Rouge, LA 70803, USA
| | - Jennifer Beseres Pollack
- Harte Research Institute for Gulf of Mexico Studies, Texas A&M University-Corpus Christi, TX, 78412, USA
| | - Morgan Kelly
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA
| | - Jerome F La Peyre
- School of Animal Sciences, Louisiana State University Agricultural Center, Baton Rouge, LA 70803, USA
- Corresponding author: School of Animal Sciences, Louisiana State University Agricultural Center, Baton Rouge, LA 70803, USA. Tel: (225) 578-5419.
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9
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Affiliation(s)
- Danielle A. Marshall
- School of Renewable Natural Resources Louisiana State University Agricultural Center Baton Rouge LA 70803 U.S.A
| | - Samuel C. Moore
- School of Renewable Natural Resources Louisiana State University Agricultural Center Baton Rouge LA 70803 U.S.A
| | - Malinda Sutor
- Department of Oceanography and Coastal Sciences Louisiana State University 2179 Energy, Coast, and Environment Bldg Baton Rouge LA 70803 U.S.A
| | - Jerome F. La Peyre
- School of Animal Sciences Louisiana State University Agricultural Center Baton Rouge LA 70803 U.S.A
| | - Megan K. La Peyre
- U.S. Geological Survey, Louisiana Cooperative Fish and Wildlife Research Unit, School of Renewable Natural Resources Louisiana State University Agricultural Center Baton Rouge LA 70803 U.S.A
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Casas SM, La Peyre JF. Heat shock protein 70 levels and post-harvest survival of eastern oysters following sublethal heat shock in the laboratory or conditioning in the field. Cell Stress Chaperones 2020; 25:369-378. [PMID: 31916124 PMCID: PMC7058772 DOI: 10.1007/s12192-019-01056-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2019] [Revised: 11/20/2019] [Accepted: 11/25/2019] [Indexed: 10/25/2022] Open
Abstract
A major problem of storing and shipping eastern oysters (Crassostrea virginica) from the Northern Gulf of Mexico in summer and early fall is their elevated mortality. A study was therefore conducted to determine whether heat shocking the oysters or conditioning them to aerial exposure prior to harvest could reduce their mortality during cold storage. Increasing the levels of stress proteins in bivalves has been shown to reduce their mortality when exposed to additional stressors. In this study, the levels of heat shock protein 70 (HSP70) proteins and cumulative mortality during cold storage, out of water, of market-sized oysters were measured, in summer, following (1) sublethal heat shocks (41 °C, 1 h) in the laboratory or (2) 3 weeks to 6 weeks of daily exposures to air (0 h, ~ 10 h, or ~ 18 h) in the field. In total, four heat shock and two aerial exposure studies were done. Consistently, heat shocks or 6 weeks of daily aerial exposures increased HSP70 levels in oysters but did not reduce their mortality during cold storage. Three weeks of daily aerial exposure did not increase HSP70 levels and only marginally reduced mortality; a significant reduction in cumulative mortality occurred in one of the aerial exposure studies after 7 days of cold storage (0 h [26%], ~ 18 h [8%]). In conclusion, upregulation of HSP70 proteins or aerial exposure during grow-out was not an effective tool in reducing the mortality of oysters harvested in summer and held in cold storage.
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Affiliation(s)
- Sandra M Casas
- School of Animal Sciences, Louisiana State University Agricultural Center, Baton Rouge, LA, 70803, USA.
| | - Jerome F La Peyre
- School of Animal Sciences, Louisiana State University Agricultural Center, Baton Rouge, LA, 70803, USA
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La Peyre JF, Casas SM, Richards M, Xu W, Xue Q. Testing plasma subtilisin inhibitory activity as a selective marker for dermo resistance in eastern oysters. Dis Aquat Organ 2019; 133:127-139. [PMID: 31019137 DOI: 10.3354/dao03344] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Recent findings have suggested that eastern oyster plasma possesses inhibitors of the protease subtilisin, which play a role in the host defense against Perkinsus marinus, a protist parasite causing dermo. A study was conducted to determine whether plasma subtilisin inhibitory activity (PSIA) could be used as a selective marker in breeding programs for dermo resistance. Eastern oysters Crassostrea virginica from 2 wild Louisiana populations shown to differ in dermo resistance were collected and their PSIA was measured. Three groups of oysters were established to spawn from each population. One group was composed of randomly sampled oysters (i.e. unselected) and the other 2 groups were composed of oysters with the highest or lowest PSIA. After spawning, progenies were deployed in October 2014 in a dermo endemic area and sampled quarterly for 2 yr to measure their mortality, growth, P. marinus infection intensity, condition index, PSIA, and the gene expression of 3 subtilisin inhibitors (cvSI-1, cvSI-2, and cvSI-3). Oyster cumulative mortalities of the progenies of all groups increased both years from April to October, concomitant with increasing P. marinus infection intensities. Mortalities and P. marinus infection intensities differed markedly between the 2 populations, but differences between the unselected and selected groups of each population were limited. Measurements of PSIA and cvSI-1, cvSI-2, and cvSI-3 gene expressions between the progenies of all groups showed few differences. CvSI-1 gene expression in surviving oysters of the most susceptible population was increased at the end of the study, adding additional support to the potential role of cvSI-1 defense against P. marinus.
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Affiliation(s)
- Jerome F La Peyre
- School of Animal Sciences, Louisiana State University Agricultural Center, Baton Rouge, Louisiana 70803, USA
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Wang H, Chen Q, La Peyre MK, Hu K, La Peyre JF. Predicting the impacts of Mississippi River diversions and sea-level rise on spatial patterns of eastern oyster growth rate and production. Ecol Modell 2017. [DOI: 10.1016/j.ecolmodel.2017.02.028] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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13
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Sethi A, Xue QG, La Peyre JF, Delatte J, Husseneder C. Dual origin of gut proteases in Formosan subterranean termites (Coptotermes formosanus Shiraki) (Isoptera: Rhinotermitidae). Comp Biochem Physiol A Mol Integr Physiol 2011; 159:261-7. [DOI: 10.1016/j.cbpa.2011.03.012] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2010] [Revised: 03/17/2011] [Accepted: 03/17/2011] [Indexed: 10/18/2022]
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Xue Q, Hellberg ME, Schey KL, Itoh N, Eytan RI, Cooper RK, La Peyre JF. A new lysozyme from the eastern oyster, Crassostrea virginica, and a possible evolutionary pathway for i-type lysozymes in bivalves from host defense to digestion. BMC Evol Biol 2010; 10:213. [PMID: 20633278 PMCID: PMC3020801 DOI: 10.1186/1471-2148-10-213] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2010] [Accepted: 07/15/2010] [Indexed: 12/02/2022] Open
Abstract
BACKGROUND Lysozymes are enzymes that lyse bacterial cell walls, an activity widely used for host defense but also modified in some instances for digestion. The biochemical and evolutionary changes between these different functional forms has been well-studied in the c-type lysozymes of vertebrates, but less so in the i-type lysozymes prevalent in most invertebrate animals. Some bivalve molluscs possess both defensive and digestive lysozymes. RESULTS We report a third lysozyme from the oyster Crassostrea virginica, cv-lysozyme 3. The chemical properties of cv-lysozyme 3 (including molecular weight, isoelectric point, basic amino acid residue number, and predicted protease cutting sites) suggest it represents a transitional form between lysozymes used for digestion and immunity. The cv-lysozyme 3 protein inhibited the growth of bacteria (consistent with a defensive function), but semi-quantitative RT-PCR suggested the gene was expressed mainly in digestive glands. Purified cv-lysozyme 3 expressed maximum muramidase activity within a range of pH (7.0 and 8.0) and ionic strength (I = 0.005-0.01) unfavorable for either cv-lysozyme 1 or cv-lysozyme 2 activities. The topology of a phylogenetic analysis of cv-lysozyme 3 cDNA (full length 663 bp, encoding an open reading frame of 187 amino acids) is also consistent with a transitional condition, as cv-lysozyme 3 falls at the base of a monophyletic clade of bivalve lysozymes identified from digestive glands. Rates of nonsynonymous substitution are significantly high at the base of this clade, consistent with an episode of positive selection associated with the functional transition from defense to digestion. CONCLUSION The pattern of molecular evolution accompanying the shift from defensive to digestive function in the i-type lysozymes of bivalves parallels those seen for c-type lysozymes in mammals and suggests that the lysozyme paralogs that enhance the range of physiological conditions for lysozyme activity may provide stepping stones between defensive and digestive forms.
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Affiliation(s)
- Qinggang Xue
- Department of Veterinary Science, Louisiana State University Agricultural Center, Baton Rouge, LA 70830, USA
| | - Michael E Hellberg
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA
| | - Kevin L Schey
- Department of Cell and Molecular Pharmacology, Medical University of South Carolina, Charleston, SC 29425, USA
- Mass Spectrometry Center, Department of Biochemistry, Vanderbilt University, Nashville, TN 37240, USA
| | - Naoki Itoh
- Department of Veterinary Science, Louisiana State University Agricultural Center, Baton Rouge, LA 70830, USA
- Graduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori Amamiya-machi, Aoba-ku, Sendai 981-8555 Miyagi, Japan
| | - Ron I Eytan
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA
| | - Richard K Cooper
- Department of Veterinary Science, Louisiana State University Agricultural Center, Baton Rouge, LA 70830, USA
| | - Jerome F La Peyre
- Department of Veterinary Science, Louisiana State University Agricultural Center, Baton Rouge, LA 70830, USA
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La Peyre MK, Casas SM, Gayle W, La Peyre JF. The combined influence of sub-optimal temperature and salinity on the in vitro viability of Perkinsus marinus, a protistan parasite of the eastern oyster Crassostrea virginica. J Invertebr Pathol 2010; 105:176-81. [PMID: 20600094 DOI: 10.1016/j.jip.2010.06.010] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2010] [Revised: 06/11/2010] [Accepted: 06/21/2010] [Indexed: 11/24/2022]
Abstract
Perkinsus marinus is a major cause of mortality in eastern oysters along the Gulf of Mexico and Atlantic coasts. It is also well documented that temperature and salinity are the primary environmental factors affecting P. marinus viability and proliferation. However, little is known about the effects of combined sub-optimal temperatures and salinities on P. marinus viability. This in vitro study examined those effects by acclimating P. marinus at three salinities (7, 15, 25 ppt) to 10 degrees C to represent the lowest temperatures generally reached in the Gulf of Mexico, and to 2 degrees C to represent the lowest temperatures reached along the mid-Atlantic coasts and by measuring changes in cell viability and density on days 1, 30, 60 and 90 following acclimation. Cell viability and density were also measured in 7 ppt cultures acclimated to each temperature and then transferred to 3.5 ppt. The largest decreases in cell viability occurred only with combined low temperature and salinity, indicating that there is clearly a synergistic effect. The largest decreases in cell viability occurred only with both low temperature and salinity after 30 days (3.5 ppt, 2 degrees C: 0% viability), 60 days (3.5 ppt, 10 degrees C: 0% viability) and 90 days (7 ppt, 2 degrees C: 0.6+/-0.7%; 7 ppt, 10 degrees C: 0.2+/-0.2%).
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Affiliation(s)
- Megan K La Peyre
- US Geological Survey, Louisiana Fish and Wildlife Cooperative Research Unit, School of Renewable Natural Resources, Louisiana State University Agricultural Center, Baton Rouge, LA 70803, USA.
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La Peyre JF, Xue QG, Itoh N, Li Y, Cooper RK. Serine protease inhibitor cvSI-1 potential role in the eastern oyster host defense against the protozoan parasite Perkinsus marinus. Dev Comp Immunol 2010; 34:84-92. [PMID: 19720077 DOI: 10.1016/j.dci.2009.08.007] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2009] [Revised: 08/21/2009] [Accepted: 08/22/2009] [Indexed: 05/28/2023]
Abstract
The serine protease inhibitor cvSI-1, purified from plasma of eastern oysters, inhibited the proliferation of the protozoan parasite Perkinsus marinus in vitro. In situ hybridization located cvSI-1 gene expression in basophil cells of the digestive tubules and cvSI-1 expression measured by real-time quantitative reverse transcriptase polymerase chain reaction was several hundred folds greater in digestive glands than in other organs examined or circulating hemocytes. cvSI-1 gene expression was also significantly greater in winter than in summer. Finally, cvSI-1 gene expression and plasma protease inhibitory activity in oysters selected for increased resistance to P. marinus were significantly greater than in unselected oysters. These findings support the hypothesis that cvSI-1 plays a role in eastern oyster host defense against P. marinus possibly through inhibition of parasite proliferation.
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Affiliation(s)
- Jerome F La Peyre
- Department of Veterinary Science, Louisiana State University Agricultural Center, Baton Rouge, LA 70803, USA.
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Xue Q, Itoh N, Schey KL, Cooper RK, La Peyre JF. Evidence indicating the existence of a novel family of serine protease inhibitors that may be involved in marine invertebrate immunity. Fish Shellfish Immunol 2009; 27:250-259. [PMID: 19464375 DOI: 10.1016/j.fsi.2009.05.006] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2009] [Revised: 04/20/2009] [Accepted: 05/12/2009] [Indexed: 05/27/2023]
Abstract
A new serine protease inhibitor, designated cvSI-2, was purified and characterized from the plasma of the eastern oyster, Crassostrea virginica. CvSI-2 inhibited the serine protease subtilisin A in a slow-tight binding manner, with an overall dissociation constant Ki* of 0.18 nM. It also inhibited perkinsin, the major extracellular protease of the oyster protozoan parasite Perkinsus marinus. Sequencing of cvSI-2 cloned cDNA revealed an open reading frame of 258 bp encoding a polypeptide of 85 amino acids, with the 18 N-terminal amino acids forming a signal peptide. The mature cvSI-2 molecule predicted consisted of 67 amino acids with 12 cysteine residues and a calculated molecular mass of 7202.96 Da. Overall 91% of the cvSI-2 amino acid sequence predicted from cDNA was confirmed by tandem mass spectrometry sequencing of purified cvSI-2. In addition, serine 43 and a threonine substitution at this position were observed. CvSI-2 amino acid sequence showed a 38% identity and 54% similarity with that of cvSI-1, the first protease inhibitor purified and characterized from a bivalve mollusc. Like cvSI-1, cvSI-2 gene was expressed in the basophil cells of digestive tubules. BLAST search found multiple ESTs from the eastern oyster, Pacific oyster, Mediterranean mussel, and sea vase, a tunicate, which could encode proteins with sequences similar to cvSI-1 and cvSI-2. Our findings indicate that cvSI-1 and cvSI-2 are members of a novel family of serine protease inhibitors in bivalve molluscs and perhaps other marine invertebrates, which share the characteristic cysteine array C-X(4-9)-C-X(4-6)-C-X(7)-C-X(4)-C-T-C-X(6-9)-C-X(5)-C-X(3-7)-C-X(6-10)-C-X(4)-C-X-C.
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Affiliation(s)
- Qinggang Xue
- Department of Veterinary Science, Louisiana State University Agricultural Center, Baton Rouge, LA 70830, USA
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Itoh N, Xue Q, Li Y, Cooper RK, La Peyre JF. cDNA cloning and tissue expression of plasma lysozyme in the eastern oyster, Crassostrea virginica. Fish Shellfish Immunol 2007; 23:957-68. [PMID: 17703954 DOI: 10.1016/j.fsi.2007.03.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2006] [Revised: 03/01/2007] [Accepted: 03/08/2007] [Indexed: 05/16/2023]
Abstract
The cDNA sequence of a 17,861 Da lysozyme first purified from plasma of eastern oysters (Crassostrea virginica) was identified and its complete amino acid sequence deduced. The amino acid sequence of the plasma lysozyme, designated cv-lysozyme 1, contained both a unique and a conserved region when compared to the amino acid sequences of other bivalve lysozymes. In situ hybridisation located cv-lysozyme 1 gene expression in mantle and gill cells in standard histological sections. Quantitative real-time RT-PCR detected cv-lysozyme 1 expression in all organs examined and circulating haemocytes. The number of cv-lysozyme 1 mRNA transcripts was particularly high in mantles and labial palps suggesting those organs are the main sites of cv-lysozyme 1 synthesis. Cv-lysozyme 1 enzyme activity measured by lysing Micrococcus lysodeikticus bacteria and expressed in units per gram tissue was highest in mantles, labial palps and gills. Most cv-lysozyme 1 enzyme activity in oysters was found in plasma. Cv-lysozyme 1 main organs of synthesis, its abundance in plasma and its strong antimicrobial properties suggest its main role is in oyster host defences.
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Affiliation(s)
- Naoki Itoh
- Cooperative Aquatic Animal Health Research Program, Department of Veterinary Science, 111 Dalrymple Building, Louisiana State University Agricultural Center, Baton Rouge, LA 70803, USA
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Xue QG, Waldrop GL, Schey KL, Itoh N, Ogawa M, Cooper RK, Losso JN, La Peyre JF. A novel slow-tight binding serine protease inhibitor from eastern oyster (Crassostrea virginica) plasma inhibits perkinsin, the major extracellular protease of the oyster protozoan parasite Perkinsus marinus. Comp Biochem Physiol B Biochem Mol Biol 2006; 145:16-26. [PMID: 16872855 DOI: 10.1016/j.cbpb.2006.05.010] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2005] [Revised: 05/26/2006] [Accepted: 05/27/2006] [Indexed: 12/20/2022]
Abstract
A serine protease inhibitor was purified from plasma of the eastern oyster, Crassostrea virginica. The inhibitor is a 7609.6 Da protein consisting of 71 amino acids with 12 cysteine residues that are postulated to form 6 intra-chain disulfide bridges. Sequencing of the cloned cDNA identified an open reading frame encoding a polypeptide of 90 amino acids, with the 19 N-terminal amino acids forming a signal peptide. No sequence similarity with known proteins was found in sequence databases. The protein inhibited the serine proteases subtilisin A, trypsin and perkinsin, the major extracellular protease of the oyster protozoan parasite, Perkinsus marinus, in a slow binding manner. The mechanism of inhibition involves a rapid binding of inhibitor to the enzyme to form a weak enzyme-inhibitor complex followed by a slow isomerization to form a very tight binding enzyme-inhibitor complex. The overall dissociation constants K(i) with subtilisin A, perkinsin and trypsin were 0.29 nM, 13.7 nM and 17.7 nM, respectively. No inhibition of representatives of the other protease classes was detected. This is the first protein inhibitor of proteases identified from a bivalve mollusk and it represents a new protease inhibitor family. Its tight binding to subtilisin and perkinsin suggests it plays a role in the oyster host defense against P. marinus.
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Affiliation(s)
- Qing-Gang Xue
- Cooperative Aquatic Animal Health Research Program, Department of Veterinary Science, Louisiana State University Agricultural Center, Baton Rouge, LA 70803, USA
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20
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Xue QG, Schey KL, Volety AK, Chu FLE, La Peyre JF. Purification and characterization of lysozyme from plasma of the eastern oyster (Crassostrea virginica). Comp Biochem Physiol B Biochem Mol Biol 2004; 139:11-25. [PMID: 15364284 DOI: 10.1016/j.cbpc.2004.05.011] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2004] [Revised: 05/24/2004] [Accepted: 05/25/2004] [Indexed: 10/26/2022]
Abstract
Lysozyme was purified from the plasma of eastern oysters (Crassostrea virginica) using a combination of ion exchange and gel filtration chromatographies. The molecular mass of purified lysozyme was estimated at 18.4 kDa by SDS-PAGE, and its isoelectric point was greater than 10. Mass spectrometric analysis of the purified enzyme revealed a high-sequence homology with i-type lysozymes. No similarity was found however between the N-terminal sequence of oyster plasma lysozyme and N-terminal sequences of other i-type lysozymes, suggesting that the N-terminal sequences of the i-type lysozymes may vary to a greater extent between species than reported in earlier studies. The optimal ionic strength, pH, cation concentrations, sea salt concentrations, and temperature for activity of the purified lysozyme were determined, as well as its temperature and pH stability. Purified oyster plasma lysozyme inhibited the growth of Gram-positive bacteria (e.g., Lactococcus garvieae, Enterococcus sp.) and Gram-negative bacteria (e.g., Escherichia coli, Vibrio vulnificus). This is a first report of a lysozyme purified from an oyster species and from the plasma of a bivalve mollusc.
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Affiliation(s)
- Qing-Gang Xue
- Cooperative Aquatic Animal Health Research Program, Department of Veterinary Science, Louisiana State University Agricultural Center, 111 Dalrymple Building, Baton Rouge, LA 70803, USA
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Gauthier JD, Jenkins JA, La Peyre JF. Flow cytometric analysis of lectin binding to in vitro-cultured Perkinsus marinus surface carbohydrates. J Parasitol 2004; 90:446-54. [PMID: 15270084 DOI: 10.1645/ge-3269] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Parasite surface glycoconjugates are frequently involved in cellular recognition and colonization of the host. This study reports on the identification of Perkinsus marinus surface carbohydrates by flow cytometric analyses of fluorescein isothiocyanate-conjugated lectin binding. Lectin-binding specificity was confirmed by sugar inhibition and Kolmogorov-Smirnov statistics. Clear, measurable fluorescence peaks were discriminated, and no parasite autofluorescence was observed. Parasites (GTLA-5 and Perkinsus-1 strains) harvested during log and stationary phases of growth in a protein-free medium reacted strongly with concanavalin A and wheat germ agglutinin, which bind to glucose-mannose and N-acetyl-D-glucosamine (GlcNAc) moieties, respectively. Both P. marinus strains bound with lower intensity to Maclura pomifera agglutinin, Bauhinia purpurea agglutinin, soybean agglutinin (N-acetyl-D-galactosamine-specific lectins), peanut agglutinin (PNA) (terminal galactose specific), and Griffonia simplicifolia II (GlcNAc specific). Only background fluorescence levels were detected with Ulex europaeus agglutinin I (L-fucose specific) and Limulus polyphemus agglutinin (sialic acid specific). The lectin-binding profiles were similar for the 2 strains except for a greater relative binding intensity of PNA for Perkinsus-1 and an overall greater lectin-binding capacity of Perkinsus-1 compared with GTLA-5. Growth stage comparisons revealed increased lectin-binding intensities during stationary phase compared with log phase of growth. This is the first report of the identification of surface glycoconjugates on a Perkinsus spp. by flow cytometry and the first to demonstrate that differential surface sugar expression is growth phase and strain dependent.
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Affiliation(s)
- Julie D Gauthier
- Department of Biological Sciences, Nicholls State University, Thibodaux, Louisiana 70310, USA.
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Casas SM, La Peyre JF, Reece KS, Azevedo C, Villalba A. Continuous in vitro culture of the carpet shell clam Tapes decussatus protozoan parasite Perkinsus atlanticus. Dis Aquat Organ 2002; 52:217-231. [PMID: 12553450 DOI: 10.3354/dao052217] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Continuous in vitro cultures of the clam Tapes decussatus parasite Perkinsus atlanticus were established from infected gill fragments, infected haemolymph and parasite hypnospores isolated from infected gill fragments following incubation in Ray's fluid thioglycollate medium (RFTM). No continuous cultures could be initiated from P. atlanticus zoospores. Cultures initiated from hypnospores yielded the highest percentage of continuous cultures (100%, 6/6), followed by cultures initiated from gill fragments (93%, 43/46) and from haemolymph (30%, 3/10). Failures to establish continuous cultures were due to microbial contamination. The source of parasite influenced the success rate, the time taken to establish cultures and the size of cultured cells. In vitro proliferation of parasite cells was mainly by vegetative multiplication. Zoosporulation, yielding motile biflagellated zoospores, was observed at a low frequency (< 1% of dividing cells) in every culture. Morphology of cultured cells examined with light and transmission electron microscopy corresponded to that of P. atlanticus found in clam tissues. Cultured cells enlarged in RFTM and stained blue-black with Lugol's solution, which are characteristics of the Perkinsus species cells. DNA sequences of the internal transcribed spacer (ITS) region of the ribosomal RNA gene complex matched those of P. atlanticus. All cultures were established in a medium designated JL-ODRP-2A that was similar in composition to the culture medium JL-ODRP-1 originally used to propagate Perkinsus marinus in vitro. Proliferation of P. atlanticus in vitro could be supported by the commercial culture medium (1:2 v/v) DME:Ham's F-12 with fetuin.
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Affiliation(s)
- Sandra M Casas
- Centro de Investigacións Mariñas, Consellería de Pesca e Asuntos Marítimos, Xunta de Galicia, Aptdo. 13, 36620 Vilanova de Arousa, Spain
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