Harmful Algae最新文献

{"title":"Genomic diversity in time and space in the toxic diatom Pseudo-nitzschia multistriata","authors":"Svenja Mager ,&nbsp;Francesco Manfellotto ,&nbsp;Antonella Ruggiero ,&nbsp;Viviana Di Tuccio ,&nbsp;Federica Cerino ,&nbsp;Stefano Accoroni ,&nbsp;Tomohiro Nishimura ,&nbsp;Marta Mikhno ,&nbsp;Neri Fattorini ,&nbsp;Timotej Turk Dermastia ,&nbsp;Jasna Arapov ,&nbsp;Sanda Skejic ,&nbsp;Lesley Rhodes ,&nbsp;Kirsty Smith ,&nbsp;Antonio Longo ,&nbsp;Caterina Manzari ,&nbsp;Lisa Campbell ,&nbsp;Graziano Pesole ,&nbsp;Remo Sanges ,&nbsp;Francesca Raffini ,&nbsp;Maria Immacolata Ferrante","doi":"10.1016/j.hal.2024.102791","DOIUrl":"10.1016/j.hal.2024.102791","url":null,"abstract":"<div><div>Understanding the origin and maintenance of genetic diversity is crucial to elucidate population dynamics of unicellular microalgae, their microevolutionary history and their adaptive ability. The planktonic, domoic acid-producing diatom <em>Pseudo-nitzschia multistriata</em> has a ubiquitous distribution in the world oceans and past population genetics studies, based on few genomic loci, have shown a clear temporal structure over different years in the Gulf of Naples (Italy). Despite the ecological and toxicological importance of this organism, detailed information on its diversity across the whole genome and at the population level is still lacking. We collected <em>P. multistriata</em> strains in the Gulf of Naples in five different years, obtained strains from the Adriatic Sea, the Gulf of Mexico and New Zealand coasts, and resequenced the whole genomes of a total of 28 strains at high coverage. While strains from the first three geographical areas were capable of producing the toxin domoic acid, the New Zealand strains had been reported to be non-toxic. A comparison of the domoic acid biosynthetic (dab) genes sequences between toxic and non-toxic strains showed very little variation among the strains, and no disrupting mutation was found in the <em>dab</em> genes in the non-toxic strains. On the other hand, the <em>dab</em> genes showed higher levels of expression in toxic strains than in non-toxic strains, suggesting that, in this species, absence of toxicity is explained by gene regulation rather than <em>dab</em> sequence divergence. Variant analysis showed stronger spatial than temporal genetic structuring and a clear separation was observed between the New Zealand strains and the others, the former having a greater content of genes under selection. Overall, the genomes of the different groups, including strains from a clonal bloom, did not appear to contain major rearrangements. Our findings contribute to enlarging our understanding of diatom diversity, a key factor underlying diatom success, and provide novel data on the longstanding problem of <em>Pseudo-nitzschia</em> toxicity.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"142 ","pages":"Article 102791"},"PeriodicalIF":5.5,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143143514","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"First description of the fish-killing raphidophyceae Chattonella marina complex in Argentina: From genetics to ichthyotoxicity unveiled","authors":"Delfina Aguiar Juárez ,&nbsp;Jorge I. Mardones ,&nbsp;Ana Flores-Leñero ,&nbsp;Luis Norambuena ,&nbsp;Javier Paredes-Mella ,&nbsp;Eugenia A. Sar ,&nbsp;Inés Sunesen","doi":"10.1016/j.hal.2025.102804","DOIUrl":"10.1016/j.hal.2025.102804","url":null,"abstract":"<div><div>Species of the harmful algal bloom (HAB)-forming genus <em>Chattonella</em> (Raphidophyceae) are responsible for massive fish kills worldwide. Despite this, the genus remains still unexplored in Argentinean waters in the Southwestern Atlantic. Three <em>Chattonella</em> strains (LPCc045, LPCc046, and LPCc047) were isolated and cultured as part of a harmful phytoplankton monitoring program in the marine coastal waters of Buenos Aires Province to determine: 1) taxonomic and genetic identification, 2) pigment compositions, and 3) ichthyotoxic potency and ROS production. Morphological observations (light and transmission electron microscopy) matched classical descriptions of <em>C. marina</em>. Phylogenetic reconstruction using a partial sequence of the ribosomal gene (LSU D1-D2) confirmed the cluster of the three strains within the <em>C. marina</em> complex clade (99 % bootstrap support). Pigment analyses by HPLC showed that the most abundant was chlorophyll-<em>a</em>, followed by fucoxanthin and other carotenoids. Gill cell damage, used as a proxy of cytotoxicity, was assessed using the rainbow trout RTgill-W1 cell-based assay against cell supernatant and intracellular treatments. Cytotoxic potency was positively correlated with cell abundance, with supernatant treatment causing more gill cell damage than intracellular content, reducing gill cell viability down to 60 % of control at 1.9 × 10³ cells mL^-1. Superoxide production was comparable with other globally distributed strains (supernatant 7.63 ± 0.67 pmol O₂^- cell^-1 h^-1; intracellular 8.1 ± 0.56 pmol O₂^- cell^-1 h^-1). This study provides the first morphological, phylogenetic, physiological and toxicological characterization of the fish-killing algae <em>C. marina</em> complex in Argentinean waters.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"142 ","pages":"Article 102804"},"PeriodicalIF":5.5,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143143510","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Evidence of global dispersal of the harmful cyanobacterium, Raphidiopsis raciborskii, in lentic freshwaters through migratory waterbirds","authors":"Zhansen Sha ,&nbsp;Huihuang Chen ,&nbsp;Lei Jin ,&nbsp;Qingping Zheng ,&nbsp;Yifan Lu ,&nbsp;Mekiso Y. Sido ,&nbsp;Anusuya Willis ,&nbsp;Cunqi Liu ,&nbsp;Jun Yang","doi":"10.1016/j.hal.2024.102786","DOIUrl":"10.1016/j.hal.2024.102786","url":null,"abstract":"<div><div>The cyanobacterium <em>Raphidiopsis raciborskii</em> has received much attention due to its global distribution and toxin production in freshwater. However, research on understanding the potential factors facilitating its geographical spread, the pattern of increasing range, and long-distance dispersal (LDD) of this species is very limited. In this study, we investigated the role of migratory waterbirds (using domesticated ducks as a proxy) and reservoirs (lentic waterbodies) in global distribution or dispersal of <em>R. raciborskii</em>. First, the global distribution of <em>R. raciborskii</em> under different reservoir scenarios was assessed through meta-analysis. The results showed a significant positive correlation between the global occurrence of <em>R. raciborskii</em> and the global number of reservoirs. Second, testing the capacity of <em>R. raciborskii</em> to spread via endozoochory or ectozoochory with ducks as a proxy of migratory waterbirds. The results indicated that <em>R. raciborskii</em> could be potentially dispersed through ectozoochory but not endozoochory, with a maximum carrying time of ∼96 hours corresponding to a maximum dispersal distance of ∼2300 km. In addition, the duck-carried <em>R. raciborskii</em> survived and could establish populations under suitable conditions. This study provides experimental evidence for the <em>R. raciborskii</em> dispersal through waterbirds. Overall, our results highlight that artificial reservoirs promote the increase of <em>R. raciborskii</em> populations, which could be dispersed across long distance via waterbird ectozoochory, thereby increasing the geographical range of <em>R. raciborskii</em>.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"142 ","pages":"Article 102786"},"PeriodicalIF":5.5,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143144651","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Phytoplankton assemblage structure, drivers, and thresholds with a focus on harmful algal bloom ecology in the Lake Okeechobee system, Florida, USA","authors":"Viviana Mazzei ,&nbsp;Kristy Lee Sullivan ,&nbsp;Keith Loftin","doi":"10.1016/j.hal.2024.102744","DOIUrl":"10.1016/j.hal.2024.102744","url":null,"abstract":"<div><div>Untangling the complexities of harmful algal bloom (HAB) dynamics is an ongoing effort that requires a fundamental understanding of spatiotemporal phytoplankton patterns and the environmental filters through which assemblages are structured. To this aim, monthly field surveys were conducted from 2019 to 2021 at 21 sites in Lake Okeechobee, Florida – a large, shallow, eutrophic, and heavily managed lake with coastal connectivity that experiences intense and recurrent HABs. Phytoplankton assemblages were strongly spatially structured forming 7 distinct lake zones with significant dissimilarity in composition and total abundance. While successional patterns were not apparent across seasons or wet/dry periods, total phytoplankton abundance was significantly greater towards the end of the wet season. Distance-based linear models using 16 abiotic variables were used to identify significant explanatory variables of spatial and temporal patterns. The spatial model explained 93 % of the variability suggesting deterministic processes largely control spatial patterns. The temporal model explained only 48 % of the temporal variability suggesting stochasticity in lake-wide shifts in assemblages over time. However, the strong spatial structuring of assemblages may preclude lake-wide succession patterns. Total algal abundance metrics were inversely related to nitrate, orthophosphate, and total alkalinity, the strongest explanatory variables of assemblage patterns, suggesting a lag between peak resources and peak abundance as phytoplankton cycle “boom-to-bust” phases. Consistent with this inverse relationship, Threshold Indicator Taxa Analysis returned almost exclusively negative responder indicator taxa for all three explanatory variable gradients. The assemblage-level threshold defined the gradient boundary between boom- and bust-associated indicator taxa. These data contribute novel information about HABs ecology pertinent to management strategies.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"142 ","pages":"Article 102744"},"PeriodicalIF":5.5,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143379148","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"High Ca2+ concentrations enhance Microcystis colony formation through upregulating polysaccharide-, energy metabolism-, and transmembrane transport-related pathways","authors":"Ping Zhang ,&nbsp;Yazhi Zhu ,&nbsp;Chao Xiong ,&nbsp;Yan Xiao ,&nbsp;Kai Li ,&nbsp;Han Wang","doi":"10.1016/j.hal.2025.102806","DOIUrl":"10.1016/j.hal.2025.102806","url":null,"abstract":"<div><div>Colony formation plays a critical role in <em>Microcystis</em> blooms. Previous studies have demonstrated that high Ca²⁺ concentrations can bring about the rapid aggregation of <em>Microcystis aeruginosa</em>, leading to the formation of colonies with morphologies resembling those observed in the wild over extended periods. However, the mechanisms through which high Ca²⁺ levels enhance colony formation remain inadequately understood. This study investigated the impact of Ca²⁺ concentrations on M<em>. aeruginosa</em> colony formation and elucidated the underlying mechanisms. The results indicated that high Ca²⁺ concentrations (≥50 mg/L) significantly enhanced colony formation, with an increase in colony size observed as Ca²⁺ concentrations rose within the range of 1–400 mg/L. In addition, the cell surface hydrophobicity and zeta potential increased with Ca²⁺ concentrations, primarily due to the augmented secretion of extracellular polymeric substances (EPS) and compression of the double electric layer. This decreased interaction energy among <em>Microcystis</em> cells and facilitated colony formation. The energy barrier decreased from 2684.35 KT to 123.64 KT as the Ca²⁺ concentration rose from 10 mg/L to 400 mg/L, indicating a significantly greater propensity for aggregation in the 400 mg/L Ca²⁺ group compared to the control. Additionally, this study found that high Ca²⁺ concentrations upregulated extracellular polysaccharide-, transmembrane transport-, and energy metabolism-related pathways while downregulating photosynthesis-related pathways. This enhanced polysaccharide content in EPS and ultimately promoted colony formation. These findings provide new insights into the role of elevated Ca²⁺ concentrations in <em>Microcystis</em> colony formation, contributing to the advancements in the knowledge of cyanobacterial bloom mechanisms.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"142 ","pages":"Article 102806"},"PeriodicalIF":5.5,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143144159","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Insight on the heterocyte patterning and the proheterocyte division in the toxic cyanobacterium Kaarinaea lacus gen. nov., sp. nov., and its genomic potential for natural products","authors":"Aniket Saraf ,&nbsp;Eddy Blondet ,&nbsp;Anne Boullié ,&nbsp;Alexis Criscuolo ,&nbsp;Muriel Gugger","doi":"10.1016/j.hal.2024.102792","DOIUrl":"10.1016/j.hal.2024.102792","url":null,"abstract":"<div><div><em>Nostoc</em> sp. 152 (= PCC 9237^T), a toxic cyanobacterium, isolated from mixed cyanobacterial bloom in a Finnish freshwater lake was reassessed using phylogenetic, morphological and genomic analyses. Multilocus and 16S rRNA gene phylogenetic analyses confirmed that this strain represents a novel Nostocalean genus for which we propose the name <em>Kaarinaea lacus</em> gen. nov., sp. nov., in accordance with the International Code of Nomenclature of Prokaryotes. The most intriguing morphological feature exhibited by PCC 9237^T is the occasional division of proheterocytes. Based on our observations, we propose a hypothesis for the sequence of events taking place leading to this phenomenon. The other interesting feature includes the unusual heterocyte patterning resulting in the development of heterocytes in series in the old culture followed by its fragmentation at this site. Among the genes involved in heterocyte differentiation and patterning, <em>patC</em> and three homologs of <em>hetP</em> were not found from the genome of PCC 9237^T. Furthermore, genomic investigations revealed a variant of heterocyte glycolipid gene cluster with a reduced <em>hglB</em>, but having additional gene coding for a protein with TubC<img>N terminal docking domain. Finally, the presence of a <em>pks2</em>-like gene cluster, whose product may interfere with the cellular differentiation, and an anachelin-like gene cluster demands further investigations.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"142 ","pages":"Article 102792"},"PeriodicalIF":5.5,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143143937","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Assessing the genomic diversity of a NW Spain bloom of Alexandrium minutum using satDNAs as chromosomal markers","authors":"Ángeles Cuadrado ,&nbsp;Marta Sixto ,&nbsp;Rosa Isabel Figueroa ,&nbsp;Alfredo de Bustos","doi":"10.1016/j.hal.2025.102801","DOIUrl":"10.1016/j.hal.2025.102801","url":null,"abstract":"<div><div><em>Alexandrium minutum</em> is a toxic dinoflagellate with numerous strains known to produce paralytic shellfish toxins (PSTs). Given the ecological importance and socio-economic impact of <em>A. minutum</em> blooms in coastal waters worldwide, this study assesses the genomic diversity by analysing clonal cultures obtained from an exceptional <em>A. minutum</em> red tide event that occurred in the Ría de Vigo (NW Atlantic coast of Spain) in 2018. To our knowledge this is the first time that satellite DNAs (satDNAs) has been used as chromosomal markers by fluorescence in situ hybridization (FISH) to analyse genomic diversity in a bloom. AmSat002-6, which is monomorphic, and AmiSat017-88 and AmiSat059-512, which colocalized with 45S rDNA can be used as markers to investigate the role of sexuality and its potential role in blooms and other factors that may influence the life cycle of <em>A. minutum</em>. Four satDNAs (AmiSat021-510, AmiSat041-75, AmiSat048-3-AAG and AmiSat060-65) are polymorphic and were used to genotype twelve clonal strains isolated from seven sites over three weeks. In addition, three <em>A. minutum</em> strains from different Mediterranean origins were genotyped. Each strain was distinguished by its unique four-satDNA genotype. Clustering and similarity analyses did not reveal any spatial or temporal grouping of the bloom strains; the dispersion was even greater than the dispersion among the Mediterranean strains, which lay between the bloom strains. The differences in the FISH patterns of sat-DNA within <em>A. minutum</em> may contribute to the assessment of genus diversification.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"142 ","pages":"Article 102801"},"PeriodicalIF":5.5,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143144163","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effects of the salinity on the growth, hemolytic activity, fatty acid content, and expression of polyketide synthase and fatty acid synthase genes of Amphidinium carterae (Dinophyceae)","authors":"Armando Mendoza-Flores ,&nbsp;Clara Elizabeth Galindo-Sánchez ,&nbsp;M. del Pilar Sánchez-Saavedra","doi":"10.1016/j.hal.2024.102788","DOIUrl":"10.1016/j.hal.2024.102788","url":null,"abstract":"<div><div>The benthic dinoflagellate <em>Amphidinium carterae</em> can produce fatty acids and polyketide compounds, such as amphidinols. Commonly, polyketides are produced by polyketides synthase (PKS), and fatty acids are produced by fatty acids synthase (FAS). The PKS and FAS genes in dinoflagellates share a common evolutionary history. This study aimed to investigate the effect of five salinities (20, 25, 30, 35, and 40 ‰) on growth, fatty acid content, hemolytic activity, and the expression of PKS and FAS genes. The results showed that low salinity (20 ‰) induces low growth in <em>A. carterae.</em> Cell size was affected by salinity, with a decrease in cell size with the salinity increase. The content of fatty acids and hemolytic compounds content increased at low salinities (20 and 25 ‰). The gene expression of the PKS genes was upregulated at high salinities (35 and 40 ‰) and downregulated at low salinities (20 and 25 ‰); FAS genes were downregulated at high (40 ‰) and low (20 ‰) salinities. The low growth rate at low salinity (20 ‰) and the high content of fatty acids and hemolytic compounds in low salinities (20 and 25 ‰) indicate that low salinities caused stress in this strain of <em>A. carterae.</em> The hemolytic activity at salinity of 20 ‰ probably due to a combinatory effect of high content of polyunsaturated fatty acids and amphidinols. To understand the relationship between gene expression and amphidinols biosynthesis requires the analysis of single-domain and multi-domain PKS.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"142 ","pages":"Article 102788"},"PeriodicalIF":5.5,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143143515","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effects of copepod chemical cues on intra- and extracellular toxins in two species of Dinophysis","authors":"Milad Pourdanandeh ,&nbsp;Véronique Séchet ,&nbsp;Liliane Carpentier ,&nbsp;Damien Réveillon ,&nbsp;Fabienne Hervé ,&nbsp;Clarisse Hubert ,&nbsp;Philipp Hess ,&nbsp;Erik Selander","doi":"10.1016/j.hal.2024.102793","DOIUrl":"10.1016/j.hal.2024.102793","url":null,"abstract":"<div><div>Copepods may contribute to harmful algal bloom formation by selectively rejecting harmful cells. Additionally, copepods and the chemical cues they exude, copepodamides, have been shown to induce increased toxin production in paralytic and amnesic toxin producing microalgae. However, it is unknown if diarrhetic shellfish toxin (DST) producers such as <em>Dinophysis</em> respond to copepods or copepodamides in a similar fashion. Here we expose laboratory cultures of <em>Dinophysis sacculus</em> and <em>D. acuminata</em> to direct grazing by <em>Acartia</em> sp. copepods or copepodamides and measure their toxins after three days. Total <em>Dinophysis</em>-produced toxins (DPTs), okadaic acid, pectenotoxin-2, and C9-diol ester of okadaic acid, increased by 8 - 45 % in <em>D. sacculus</em> but was significantly different from controls only in the highest (10 nM) copepodamide treatment whereas toxin content was not affected in <em>D. acuminata</em>. Growth rate was low across all groups and explained up to 91 % of the variation in toxin content. DPTs were redistributed from internal compartments to the extracellular medium in the highest copepodamide treatments (5 - 10 nM), which were two to three times higher than controls and indicates an active release or passive leakage of toxins. Untargeted analysis of endometabolomes indicated significant changes in metabolite profiles for both species in response to the highest copepodamide treatments, independent of known toxins. However, it is not clear whether these are stress responses or caused by more complex mechanisms. The relatively small grazer-induced effect in <em>Dinophysis</em> observed here, compared to several species of <em>Alexandrium</em> and <em>Pseudo-nitzschia</em> reported previously, suggests that DPT production in <em>Dinophysis</em> is likely not induced by copepods, except perhaps in patches with high copepod densities. Thus, DPTs may, represent either a constitutive chemical defence for <em>Dinophysis</em>, or serve an altogether different purpose.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"142 ","pages":"Article 102793"},"PeriodicalIF":5.5,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143143553","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Transcriptional regulation of the cylindrospermopsin biosynthesis (cyr) gene cluster in Raphidiopsis raciborskii AWT205","authors":"Alescia Cullen ,&nbsp;Leanne A. Pearson ,&nbsp;Sarah E. Ongley ,&nbsp;Nathan D. Smith ,&nbsp;Brett A. Neilan","doi":"10.1016/j.hal.2024.102783","DOIUrl":"10.1016/j.hal.2024.102783","url":null,"abstract":"<div><div>Cyanobacterial harmful algal blooms (HABs), producing the hepatotoxin cylindrospermopsin (CYN), are among the most frequently reported globally. Although the gene cluster encoding CYN biosynthesis (<em>cyr</em>) has been sequenced, many aspects of CYN regulation are unresolved. This study investigates <em>cyr</em> transcriptional regulation in the cyanobacterium, <em>Raphidiopsis raciborskii</em> AWT205, through <em>in silico</em> analysis, reverse transcription quantitative PCR (RT-qPCR), and DNA-affinity capture assays (DACAs). While <em>in silico</em> analysis identified binding sites for environmentally responsive transcription factors throughout the <em>cyr</em> cluster, DACAs captured the binding of AbrB (a transcription factor that regulates the cyanobacterial response to nitrogen and iron availability) to the <em>cyrD</em> promoter. Surprisingly, the initiating cylindrospermopsin synthetase, CyrA, was also captured by the <em>cyrD</em> promoter probe. This is the first experimental evidence of CYN (and cyanotoxin) autoregulation. Our study is also the most extensive investigation of <em>cyr</em> transcription, concurrently targeting nine <em>cyr</em> genes across three growth stages. We found significant heterogeneity between transcription levels of each <em>cyr</em> gene, which also varied across different growth stages. Surprisingly, the ratio of <em>cyrI</em> (hydroxylase) to <em>cyrJ</em> (sulfotransferase) transcripts was inversely proportional to the ratio of deoxyCYN to CYN. Taken together, the results of this study suggest that transcription of the <em>cyr</em> gene cluster in <em>R. raciborskii</em> AWT205 is driven by multiple promoters and DNA-binding proteins, that can be responsive to changing environmental conditions. However, the production of different CYN variants did not correlate to transcription alone, with additional regulatory mechanisms proposed.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"142 ","pages":"Article 102783"},"PeriodicalIF":5.5,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143144652","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}