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Chen T, Zhang H, Dong W, Bu K, Chen X. Toxin production and transcriptomic response to nitrate concentrations in the toxic dinoflagellate Alexandrium tamarense. MARINE ENVIRONMENTAL RESEARCH 2024; 198:106550. [PMID: 38820827 DOI: 10.1016/j.marenvres.2024.106550] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2023] [Revised: 04/22/2024] [Accepted: 05/09/2024] [Indexed: 06/02/2024]
Abstract
The bloom-forming dinoflagellate Alexandrium tamarense is one of the most important producers of paralytic shellfish poisoning toxins. Annually recurrent blooms of this dinoflagellate species is associated with the incremental nitrogen influx, especially excessive nitrate input. However, limited studies have been conducted on the toxin production and underlying molecular regulation mechanisms of A. tamarense under various nitrate (N) conditions. Therefore, toxin production and transcriptomic responses of this species were investigated. The toxin profile of A. tamarense was consistently dominated by the C2-toxins, and the cellular toxicity increased with N concentrations peaking at 9.23 ± 0.03 fmol/cell in the 883 μM N-added group. Under lower N conditions, expressions of two STX-core genes, sxtA and sxtG, were significantly down-regulated, suggesting that N regulated sxt expression and triggered responses related to toxin biosynthesis. Results of this study provided valuable insights into the ecophysiology of A. tamarense, enhancing our understanding of the occurrence of toxification events in natural environments.
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Affiliation(s)
- Tiantian Chen
- College of Environmental Science and Engineering, Ocean University of China, Qingdao, 266100, China; Key Laboratory of Marine Environment and Ecology, Ocean University of China, Qingdao, 266100, China
| | - Han Zhang
- College of Environmental Science and Engineering, Ocean University of China, Qingdao, 266100, China; Key Laboratory of Marine Environment and Ecology, Ocean University of China, Qingdao, 266100, China
| | - Wenlong Dong
- Shandong Marine Forecast and Hazard Mitigation Service, Qingdao, 266100, China
| | - Kexin Bu
- College of Environmental Science and Engineering, Ocean University of China, Qingdao, 266100, China; Key Laboratory of Marine Environment and Ecology, Ocean University of China, Qingdao, 266100, China
| | - Xi Chen
- College of Marine Life Sciences, Ocean University of China, Qingdao, 266003, China.
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Bui QTN, Pradhan B, Kim HS, Ki JS. Environmental Factors Modulate Saxitoxins (STXs) Production in Toxic Dinoflagellate Alexandrium: An Updated Review of STXs and Synthesis Gene Aspects. Toxins (Basel) 2024; 16:210. [PMID: 38787062 PMCID: PMC11125744 DOI: 10.3390/toxins16050210] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2024] [Revised: 04/23/2024] [Accepted: 04/28/2024] [Indexed: 05/25/2024] Open
Abstract
The marine dinoflagellate Alexandrium is known to form harmful algal blooms (HABs) and produces saxitoxin (STX) and its derivatives (STXs) that cause paralytic shellfish poisoning (PSP) in humans. Cell growth and cellular metabolism are affected by environmental conditions, including nutrients, temperature, light, and the salinity of aquatic systems. Abiotic factors not only engage in photosynthesis, but also modulate the production of toxic secondary metabolites, such as STXs, in dinoflagellates. STXs production is influenced by a variety of abiotic factors; however, the relationship between the regulation of these abiotic variables and STXs accumulation seems not to be consistent, and sometimes it is controversial. Few studies have suggested that abiotic factors may influence toxicity and STXs-biosynthesis gene (sxt) regulation in toxic Alexandrium, particularly in A. catenella, A. minutum, and A. pacificum. Hence, in this review, we focused on STXs production in toxic Alexandrium with respect to the major abiotic factors, such as temperature, salinity, nutrients, and light intensity. This review informs future research on more sxt genes involved in STXs production in relation to the abiotic factors in toxic dinoflagellates.
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Affiliation(s)
- Quynh Thi Nhu Bui
- Department of Life Science, Sangmyung University, Seoul 03016, Republic of Korea; (Q.T.N.B.); (H.-S.K.)
| | - Biswajita Pradhan
- Department of Biotechnology, Sangmyung University, Seoul 03016, Republic of Korea;
- Department of Botany, Model Degree College, Rayagada 765017, Odisha, India
| | - Han-Sol Kim
- Department of Life Science, Sangmyung University, Seoul 03016, Republic of Korea; (Q.T.N.B.); (H.-S.K.)
| | - Jang-Seu Ki
- Department of Life Science, Sangmyung University, Seoul 03016, Republic of Korea; (Q.T.N.B.); (H.-S.K.)
- Department of Biotechnology, Sangmyung University, Seoul 03016, Republic of Korea;
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Bui QTN, Kim HS, Ki JS. Polyphyletic origin of saxitoxin biosynthesis genes in the marine dinoflagellate Alexandrium revealed by comparative transcriptomics. HARMFUL ALGAE 2024; 134:102620. [PMID: 38705616 DOI: 10.1016/j.hal.2024.102620] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2023] [Revised: 02/26/2024] [Accepted: 03/15/2024] [Indexed: 05/07/2024]
Abstract
The marine dinoflagellate Alexandrium is known to form harmful algal blooms, and at least 14 species within the genus can produce saxitoxins (STXs). STX biosynthesis genes (sxt) are individually revealed in toxic dinoflagellates; however, the evolutionary history remains controversial. Herein, we determined the transcriptome sequences of toxic Alexandrium (A. catenella and A. pacificum) and non-toxic Alexandrium (A. fraterculus and A. fragae) and characterized their sxt by focusing on evolutionary events and STX production. Comparative transcriptome analysis revealed higher homology of the sxt in toxic Alexandrium than in non-toxic species. Notably, non-toxic Alexandrium spp. were found to have lost two sxt core genes, namely sxtA4 and sxtG. Expression levels of 28 transcripts related to eight sxt core genes showed that sxtA, sxtG, and sxtI were relatively high (>1.5) in the toxic group compared to the non-toxic group. In contrast, the non-toxic group showed high expression levels in sxtU (1.9) and sxtD (1.7). Phylogenetic tree comparisons revealed distinct evolutionary patterns between 28S rDNA and sxtA, sxtB, sxtI, sxtD, and sxtU. However, similar topology was observed between 28S rDNA, sxtS, and sxtH/T. In the sxtB and sxtI phylogeny trees, toxic Alexandrium and cyanobacteria were clustered together, separating from non-toxic species. These suggest that Alexandrium may acquire sxt genes independently via horizontal gene transfer from toxic cyanobacteria and other multiple sources, demonstrating monocistronic transcripts of sxt in dinoflagellates.
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Affiliation(s)
- Quynh Thi Nhu Bui
- Department of Life Science, Sangmyung University, Seoul 03016, South Korea
| | - Han-Sol Kim
- Department of Life Science, Sangmyung University, Seoul 03016, South Korea
| | - Jang-Seu Ki
- Department of Life Science, Sangmyung University, Seoul 03016, South Korea.
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Kim HS, Kim T, Park J, Park TG, Ki JS. Development of saxitoxin biosynthesis gene sxtB-targeted qPCR assay for the quantification of toxic dinoflagellates Alexandrium catenella (group I) and A. pacificum (group IV) occurring in the Korean coast. HARMFUL ALGAE 2024; 134:102603. [PMID: 38705609 DOI: 10.1016/j.hal.2024.102603] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2023] [Revised: 02/07/2024] [Accepted: 02/16/2024] [Indexed: 05/07/2024]
Abstract
Toxic dinoflagellate Alexandrium can produce saxitoxins (STXs) and cause paralytic shellfish poisoning (PSP), and thus they are monitored for environmental safety management. Microscopic discrimination of dinoflagellates is difficult to distinguish between toxic and non-toxic species due to their similar morphology. Meanwhile, an alternative quantitative PCR (qPCR) assay is sensitive, rapid, and cost-effective for harmful species monitoring. Herein, we developed a novel qPCR assay to detect the STXs biosynthesis gene sxtB of Alexandrium catenella and A. pacificum, the leading cause of PSP outbreaks in Asian coasts and worldwide. The newly designed sxtB TaqMan probes target the species without any positive signal in other relative dinoflagellates. Deming regression analysis revealed that the sxtB copy number of A. catenella and A. pacificum was 3.6 and 4.1 copies per cell, respectively. During the blooming periods (April 13th-14th, 2020), only A. catenella cells were detected through the qPCR assay, ranging from 5.0 × 10 to 2.5 × 104 eq cells L-1. In addition, sxtB qPCR quantified more accurately compared to large subunit (LSU) rRNA targeting qPCR assay that overestimate cell density. Besides, the sensitivity of sxtB was higher compared to the microscope when the species were rarely present (5.0 × 102 cells L-1). These suggest that the sxtB qPCR assay can be applied to toxic Alexandrium monitoring in the Korean coast, even in the early stage of bloomings.
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Affiliation(s)
- Han-Sol Kim
- Department of Life Science, Sangmyung University, Seoul 03016, Korea
| | - Taehee Kim
- Department of Life Science, Sangmyung University, Seoul 03016, Korea
| | - Jaeyeon Park
- Environment & Resource Convergence Center, Advanced Institute of Convergence Technologies, Suwon 16229, Korea
| | - Tae Gyu Park
- National Institute of Fisheries Science (NIFS), Busan 46083, Korea
| | - Jang-Seu Ki
- Department of Life Science, Sangmyung University, Seoul 03016, Korea.
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Park H, Kim HS, Abassi S, Bui QTN, Ki JS. Two novel glutathione S-transferase (GST) genes in the toxic marine dinoflagellate Alexandrium pacificum and their transcriptional responses to environmental contaminants. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 915:169983. [PMID: 38215848 DOI: 10.1016/j.scitotenv.2024.169983] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2023] [Revised: 01/02/2024] [Accepted: 01/05/2024] [Indexed: 01/14/2024]
Abstract
The present study identified two novel glutathione S-transferase (GST) genes from the toxic dinoflagellate Alexandrium pacificum and examined their molecular characteristics and transcriptional responses to algicides and environmental contaminants. Bioinformatic analysis revealed that both ApGSTs are cytosolic, belonging to the chi-like class (ApGST1) and an undefined class (ApGST2). The overall expression of ApGSTs showed similar patterns depending on the exposed contaminants, while they were differently regulated by polychlorinated biphenyl (PCB). Copper treatments (CuCl2 and CuSO4) did not significantly induce the expression of ApGSTs. The highest up-regulations of ApGST1 and ApGST2 were under 6-h treatments of 0.10 and 0.50 mg L-1 NaOCl. Interestingly, only ApGST1 increased significantly after 0.10, 0.50, and 1.00 mg L-1 of PCB exposure (6 h). Intracellular reactive oxygen species (ROS) increased considerably under NaOCl; however, it was not significantly higher in the PCB-treated cells. GST activity was increased by NaOCl and PCB treatments, but only PCB caused apoptosis. These results suggest that GSTs are involved in the first line of phase II detoxification, protecting dinoflagellate cells against oxidative damage.
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Affiliation(s)
- Hyunjun Park
- Department of Life Science, Sangmyung University, Seoul, South Korea
| | - Han-Sol Kim
- Department of Life Science, Sangmyung University, Seoul, South Korea
| | - Sofia Abassi
- Department of Life Science, Sangmyung University, Seoul, South Korea
| | - Quynh Thi Nhu Bui
- Department of Life Science, Sangmyung University, Seoul, South Korea
| | - Jang-Seu Ki
- Department of Life Science, Sangmyung University, Seoul, South Korea; Department of Biotechnology, Sangmyung University, Seoul, South Korea.
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Rahav E, Herut B. Impact of combined seawater warming and triazine-type herbicide pollution on the physiology and potential toxicity of the dinoflagellate Alexandrium minutum. MARINE POLLUTION BULLETIN 2023; 196:115612. [PMID: 37837785 DOI: 10.1016/j.marpolbul.2023.115612] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2023] [Revised: 09/11/2023] [Accepted: 09/30/2023] [Indexed: 10/16/2023]
Abstract
Coastal phytoplankton communities are often exposed to multiple anthropogenic stressors simultaneously. Here, we experimentally examined how temperature increase (20-26 °C) and triazine-type herbicides pollution (500 ng terbutryn L-1), both recognized as emerging stressors, affect the abundance, physiology and selected saxitoxin gene expression in the toxic dinoflagellate Alexandrium minutum. The results show that A. minutum is more susceptible to terbutryn pollution with increasing temperatures, resulting in a significant decline in its abundance (∼80 %) and photosynthetic activity (∼40 %), while saxitoxin gene expression increased (1.5-2.5-fold). This suggests that in warming polluted coastal areas where A. minutum is often found, saxitoxin poisoning may occur even in the absence of a massive bloom. Our results recommend the development of science-based monitoring practices for algal dissolved toxins in coastal waters and estuaries, supporting environmental policies under warming and contaminated coastal regions.
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Affiliation(s)
- Eyal Rahav
- Israel Oceanographic and Limnological Research, National Institute of Oceanography, Haifa, Israel 310800.
| | - Barak Herut
- Israel Oceanographic and Limnological Research, National Institute of Oceanography, Haifa, Israel 310800
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