Search Results (661)

Protein degradation plays a fundamental role in maintaining protein homeostasis and ensures proper cellular function by regulating protein quality and quantity. Heat shock protein 100 (Hsp100), found in bacteria, plants, and fungi, is a unique chaperone family responsible for rescuing misfolded proteins from aggregated states in an ATP-dependent manner. To date, they are primarily known to mediate heat stress adaptation and enhance cellular survival under extreme conditions in higher plants and algae. Resting cyst formation in dinoflagellates is widely recognized as a response to adverse conditions, which offers an adaptive advantage to endure harsh environmental extremes that are unsuitable for vegetative cell growth and survival. In this study, based on a full-length cDNA sequence, we characterized an Hsp100 gene (SaHsp100) from the cosmopolitan bloom-forming dinoflagellate Scrippsiella acuminata, aiming to examine its life stage-specific expression patterns and preliminarily explore its potential functions. The qPCR results revealed that Hsp100 transcript levels were significantly elevated in newly formed resting cysts compared to vegetative cells and continued to increase during storage under simulated marine sediment conditions (darkness, low temperature, and anoxia). Parallel reaction monitoring (PRM)-based quantification further confirmed that Hsp100 protein levels were significantly higher in resting cysts than in vegetative cells and increased after three months of storage. These findings collectively highlighted the fundamental role of Hsp100 in the alteration of the life cycle and dormancy maintenance of S. acuminata, likely by enhancing stress adaptation and promoting cell survival through participation in proteostasis maintenance, particularly under natural sediment-like conditions that trigger severe abiotic stress. Our work deepens the current understanding of Hsp family members in dinoflagellates, paving the way for future investigations into their ecological relevance within this ecologically significant group. Full article

Kleptoplastidy is a nutrition mode in which cells of protists and some multicellular organisms acquire, maintain, and exploit chloroplasts of prey algae cells as photosynthesis reactors. It is an important aspect of the mixotrophic feeding strategy, which plays a role in the formation of harmful algae blooms (HABs). We developed a new mathematical model, in which kleptoplastidy is regarded as a mechanism of enhancing mixotrophy of protists. The model is constructed using three thought (theoretical) experiments and the concept of biological time. We propose to measure the contribution of kleptoplastidy to mixotrophy using a new ecological indicator: the kleptoplastidy index. This index is a function of two dimensionless variables, one representing the ratio of photosynthetic production of acquired chloroplasts versus native chloroplasts, and the other representing the balance between autotrophic and heterotrophic feeding modes. The index is tested by data for the globally distributed, bloom-forming potentially toxic mixotrophic dinoflagellates Prorocentrum cordatum. The model supports our hypothesis that kleptoplastidy can increase the division rate of algae significantly (by 40%), thus boosting their population growth and promoting blooms. The proposed model can contribute to advancements in ecological modeling aimed at forecasting and management of HABs that deteriorate marine coastal environments worldwide. Full article

To identify differentially abundant polyketide synthases (PKSs) and to characterize the biochemical consequences of brevetoxin biosynthesis, bottom-up, TMT-based quantitative proteomics and redox proteomics were conducted to compare two strains of the Florida red tide dinoflagellate Karenia brevis, which differ significantly in their brevetoxin content. Forty-eight PKS enzymes potentially linked to brevetoxin production were identified, with thirty-eight showing up to 16-fold higher abundance in the high-toxin strain. A pronounced shift toward a more oxidized redox state was observed in this strain’s proteome. Notably, 25 antioxidant-related proteins were significantly elevated, including alternative oxidase (AOX), which increased by 17-fold. These results elucidate the cellular consequences of toxin biosynthesis in K. brevis, offer new leads for the study of brevetoxin biosynthesis, and suggest a novel red tide mitigation approach targeting high toxin-producing strains. Full article

In this study, we integrated HSQC-based DeepSAT with UPLC-MS/MS to guide the isolation of omega-3 polyunsaturated fatty acid derivatives (PUFAs) from marine resources. Through this approach, four new (1–4) and nine known (5–13) PUFA analogues were obtained from large-scale cultures of the marine dinoflagellate Prorocentrum lima, with lipidomic profiling identifying FA18:5 (5), FA18:4 (7), FA22:6 (8), and FA22:6 methyl ester (11) as major constituents of the algal oil extract. Structural elucidation was achieved through integrated spectroscopic analyses of IR, 1D and 2D NMR, and HR-ESI-MS data. Given the pivotal role of microglia in Alzheimer’s disease (AD) pathogenesis, we further evaluated the neuroprotective potential of these PUFAs by assessing their regulatory effects on critical microglial functions in human microglia clone 3 (HMC3) cells, including chemotactic migration and amyloid-β42 (Aβ42) phagocytic clearance. Pharmacological evaluation demonstrated that FA20:5 butanediol ester (1), FA18:5 (5), FA18:4 (7), FA22:6 (8), and (Z)-10-nonadecenoic acid (13) significantly enhanced HMC3 migration in a wound-healing assay. Notably, FA18:4 (7) also significantly promoted Aβ42 phagocytosis by HMC3 microglia while maintaining cellular viability and avoiding pro-inflammatory activation at 20 μM. Collectively, our study suggests that FA18:4 (7) modulates microglial function in vitro, indicating its potential to exert neuroprotective effects. Full article

The Arabian Gulf, bordered by major energy-producing nations, harbors diverse microalgal communities with strong potential for the bioremediation of environmental pollutants, particularly petroleum hydrocarbons. This review evaluates two key microalgal groups—micro-green algae and dinoflagellates—highlighting their distinct physiological traits and ecological roles in pollution mitigation. Dinoflagellates, including Prorocentrum and Protoperidinium, have demonstrated hydrocarbon-degrading abilities but are frequently linked to harmful algal blooms (HABs), marine toxins, and bioluminescence, posing ecological and health risks. The toxins produced by these algae can be hemolytic or neurotoxic and include compounds such as azaspiracids, brevetoxins, ciguatoxins, okadaic acid, saxitoxins, and yessotoxins. In contrast, micro-green algae such as Oedogonium and Pandorina are generally non-toxic, seldom associated with HABs, and typically found in clean freshwater and brackish environments. Some species, like Chlorogonium, indicate pollution tolerance, while Dunaliella has shown promise in remediating contaminated seawater. Both groups exhibit unique enzymatic pathways and metabolic mechanisms for degrading hydrocarbons and remediating heavy metals. Due to their respective phycoremediation capacities and environmental adaptability, these algae offer sustainable, nature-based solutions for pollution control in coastal, estuarine, and inland freshwater systems, particularly in mainland Qatar. This review compares their remediation efficacy, ecological impacts, and practical limitations to support the selection of effective algal candidates for eco-friendly strategies targeting petroleum-contaminated marine environments. Full article

Saxitoxin (STX) is a potent toxin produced by marine dinoflagellates and freshwater or brackish water cyanobacteria, and is a member of the paralytic shellfish toxins (PSTs). As a highly specific blocker of voltage-gated sodium channels (NaVs), STX blocks sodium ion influx, thereby inhibiting nerve impulse transmission and leading to systemic physiological dysfunctions in the nervous, respiratory, cardiovascular, and digestive systems. Severe exposure can lead to paralysis, respiratory failure, and mortality. STX primarily enters the human body through the consumption of contaminated shellfish, posing a significant public health risk as the causative agent of paralytic shellfish poisoning (PSP). Beyond its acute toxicity, STX exerts cascading impacts on food safety, marine ecosystem integrity, and economic stability, particularly in regions affected by harmful algal blooms (HABs). Moreover, the complex molecular structure of STX—tricyclic skeleton and biguanide group—and its diverse analogs (more than 50 derivatives) have made it the focus of research on natural toxins. In this review, we traced the discovery history, chemical structure, molecular biosynthesis, biological enrichment mechanisms, and toxicological actions of STX. Moreover, we highlighted recent advancements in the potential for detection and treatment strategies of STX. By integrating multidisciplinary insights, this review aims to provide a holistic understanding of STX and to guide future research directions for its prevention, management, and potential applications. Full article

The parasitic dinoflagellate Hematodinium is an infectious pathogen that causes severe enzootic in numerous economically important marine crustaceans worldwide. Previous research has focused on investigating the identification and life stages of Hematodinium parasites, while the parasite abundance and tissue proliferation process of Hematodinium in naturally infected crustacean hosts need to be further studied. In the present study, the tissue tropisms and intensity of H. perezi were investigated in the naturally infected Chinese swimming crabs Portunus trituberculatus by both the qualitative (hemolymph assay, histology) and quantitative analysis (cell count, quantitative PCR). The results showed that in P. trituberculatus with infection level I (4 ± 2 parasites in 200× microscopic field), filamentous trophonts were observed in the hemolymph and stomach tissues, with the average parasite number and ITS 1 copy number of H. perezi quantitatively detected in hemolymph (1.0 × 10² parasites/mL) and stomach tissues (1.7 × 10³ cells/g), respectively. H. perezi trophonts were observed in the hemolymph (4.3 × 10⁴ parasites/mL) and exhibited broad distribution in multiple tissues with its highest abundance of H. perezi in pereiopod muscles (1.1 × 10⁴ cells/g) followed by that in stomach (4.8 × 10³ cells/g) in P. trituberculatus with infection level II (80 ± 10 parasites in 200× microscopic field). In P. trituberculatus with infection level III (200 ± 35 parasites in 200× microscopic field), a high abundance of H. perezi sporoblasts was found in the hemolymph (3.1 × 10⁷ parasites/mL) and all of the other examined tissues, with its highest abundance detected in pereiopod muscles (3.5 × 10⁴ cells/g). In addition, the number of host’s hemocytes was significantly decreased during the Hematodinium infection. This study provides a comprehensive quantitative characterization of the tissue distribution and abundance of H. perezi in its natural crab host which will contribute to better understanding of the crustacean host–Hematodinium interactions. Full article

Polyketides (PKs) are a widespread class of secondary metabolites with recognised pharmacological properties. These molecules are abundantly produced in the marine environment, especially by dinoflagellate-photosynthetic organisms able to produce several PKs, including neurotoxins, cytotoxins, and immunomodulating agents. The biosynthesis of these compounds is driven by a conserved enzymatic process involving polyketide synthase complexes. Different genera of dinoflagellates produce PKs. Among them, dinoflagellates of the genus Amphidinium are of particular interest due to its ability to produce the following two major families of PKs: amphidinolides and amphidinols. These compounds display remarkable biological activities, including anticancer, antimicrobial, and antifungal effects, making them attractive targets for pharmaceutical research and development. However, the natural yield of Amphidinium-derived polyketides (APKs) is generally low, limiting their potential for sustainable molecular farming. This challenge has prompted interest in developing biotechnological strategies to enhance their production. This review aims to define the current state of studies about APKs, starting from their initial discoveries to the recent understanding of their biosynthetic pathways. Additionally, it summarizes the structures of compounds discovered, highlights their biotechnological potential, and discusses novel trends in their production. Full article

Dinoflagellates significantly contribute to the carbon fixation and microbial loop in the ocean with high ecological diversity. While the microbial communities associated with the HABs of dinoflagellates have attracted intensive attention in recent years, little attention has been paid to the microbiomes associated with resting cysts, an important stage in the life cycle and bloom initiation dynamics of dinoflagellates. Using Scrippsiella acuminata as a representative of cyst producers and cyst-relevant research in dinoflagellates, we surveyed the bacteria and fungi microbiomes long associated with different life cycle stages of the dinoflagellate culture through 16S and ITS rRNA amplicon sequencing, and predicted their possible functions using the PICRUSt2 algorithm. The results found high species diversity of the associated bacteria–fungi microbiomes, and species featured with diverse and flexible metabolic capabilities that have stably co-occurred with the laboratory culture of S. acuminata. The host-attached and the free-living groups of bacteria–fungi microbiomes, as operationally defined in the context, showed significant differences in terms of their nutritional preferences. The bacteria–fungi species diversity and community structure associated with cysts are also distinguished significantly from that with vegetative cells, with the latter attracting more bacteria–fungi species specializing in phosphate solubilization. These results suggest that the relative species abundance and thus the community structure of the host-associated microbiome shift with the transition of life cycle stages and environmental conditions. Our findings show the association tightness between bacteria–fungi microbiomes and dinoflagellate hosts and the different life stages of hosts shaping the bacteria–fungi communities, which result in dynamic and specific interactions between bacteria–fungi microbiomes and their hosts. Full article

The non-consumptive effects of past predator exposure on phytoplankton have gained recognition, but how these effects are modulated by resource availability requires further study. We examined the simultaneous effects of past predator exposure (direct, indirect, and no exposure) and nutrient regime (combinations of N- and P-repletion and limitation) on the paralytic shellfish toxin retention and cell growth rate of a toxic dinoflagellate, Alexandrium catenella (strain BF-5), under a laboratory-simulated bloom condition (exponential, stationary, and declining phases). Within a past predator exposure treatment, cell toxin retention was generally higher under N-replete than N-limited conditions. The cells of past direct predator exposure treatment retained or produced more toxin than those in the indirect-exposure or no-exposure treatments regardless of nutrient regime in the exponential and stationary phase. By contrast, cells directly exposed to predators showed lower growth rates than the other two treatments, and also showed a tradeoff between toxin retention rate and growth rate. Separate experiments also showed that the effect of past predator exposure on reducing cell growth is stronger under N repletion than N limitation. These results imply that the interactions of past predator exposure and resource availability impact bloom dynamics and toxin transfer in the food web. Full article

Dinoflagellates are unicellular organisms that are crucial components of aquatic ecosystems, known as important primary producers and causes of harmful blooms. They have complex life cycles, including immotile stages, which contribute to their distribution and survival in unfavorable conditions. Temperature changes, primarily cold stress, significantly impact dinoflagellate physiology, influencing metabolic processes, growth rates, and encystment/excystment cycles. This study investigates the transcriptome of temporary cold-induced cysts in the marine planktonic dinoflagellate Prorocentrum cordatum. We compared gene expression in cysts subjected to a 7-h cold incubation with those returned to standard cultivation conditions and motile vegetative cells. Our results showed a marked predominance of downregulated genes in cold-induced cysts. Encystment affected signaling pathways, including calcium and protein kinase signaling, as well as RNA and protein metabolism. Upon returning to standard conditions, RNA metabolism was reactivated; upregulation of genes encoding some calcium-binding proteins and kinases was observed. Additionally, we analyzed RNA-binding pentatricopeptide repeat-containing proteins, the genes encoding which changed their expression in P. cordatum cysts, for similarities to plant MRL1 proteins. Finally, we focused on MEI2-like proteins to confirm their role in non-sexual cyst formation and position them within the diversity of MEI2 homologs in dinoflagellates. Full article

The unarmored dinoflagellate Akashiwo sanguinea is a cosmopolitan harmful algal species known for forming intense blooms leading to mass mortality of fish, shellfish, and seabirds. Globally distributed populations of A. sanguinea have been classified into four ribotypes based on their characteristic sequences in LSU rRNA gene and primary geographic distributions. In this study, we compared the bacterial communities co-existing with the six strains of A. sanguinea from China and the USA (belonging to two ribotypes) using high-throughput sequencing of 16S rRNA gene amplicons. Generally, a bacterial microbiome with high diversity was found to be associated with laboratory-cultured A. sanguinea strains from different geographic origins. Based on ribotype classification, the six samples were divided into two groups (ribotype A: AsCHINA; ribotype C: AsUSA) for subsequent comparative analyses of their bacterial communities. Beta diversity analysis revealed a clear separation between the two groups, reflecting significant differences in bacterial community composition between the two ribotypes. Significantly higher abundance of nitrogen-fixing bacteria was found in the AsUSA group, suggesting that ribotype C may benefit from external nitrogen sources provided by their bacterial associates. If this also holds true in natural environments, this nitrogen-fixing partnership likely confers a competitive advantage to ribotype C in oligotrophic offshore waters, and potentially extends bloom duration when environmental nitrogen is depleted. Our study raised the possibility that different ribotypes of A. sanguinea may harbor distinct prokaryotic microbiomes in their phycospheres under stable cultivation conditions. Further comprehensive comparison among more isolates across all four ribotypes is highly necessary to validate this hypothesis. Full article

An oceanographic cruise with 34 stations was conducted in the central-southwestern region of the Gulf of Mexico from February 19 to 10 March 2013. This study included the measurement of hydrographic and phytoplankton bio-optical parameters, and pigment samples were collected at two depth levels (10 and 50 m). Our results showed a warm and nutrient-depleted water column associated with low chlorophyll a (<1 mg Chla m⁻³) and average values of a_ph440 (0.01 ± 0.008, m⁻¹) and a_d350 (0.04 ± 0.02, m⁻¹). In addition, nano-microphytoplankton abundance and pigments were analyzed using a light microscope and HPLC, respectively. Overall, the Gulf of Mexico exhibited oligotrophic characteristics, with Chla (0.17 ± 0.11 mg m⁻³) and NO₃⁻ (0.03 ± 0.001 µM), except at 50 m depth in some stations north of Yucatán and in Campeche Bay and at surface level off the Tamaulipas shelf. In these three regions, values of a_ph(440), a_d(350), (Chla) and phytoplankton abundance (>12 × 10³ cells L⁻¹) were observed near river mouths and under seasonal oceanographic forcings, which increased the growth and diversity of phytoplankton. The most relevant pigments found were DVchla (0.06 ± 0.13 mg m⁻³), Chlb (0.16 ± 0.21 mg m⁻³), Zea (0.06 ± 0.03 mg m⁻³), and Hex-fuco (0.02 ± 0.02 mg m⁻³); these are associated with the presence of Prochlorococcus, chlorophytes, Synechococcus, prymnesiophytes, and diatoms. Through the bio-optical variability, we determined the ecological geography of phytoplankton in four different spectral shapes, where M1 and M2 represent the group of cyanobacteria (Prochlorococcus and Synechococcus) and M3 and M4 represent a mixture of diatoms, dinoflagellates, and chlorophytes. In conclusion, we consider that oceanographic processes such as cyclonic and anticyclonic structures and permanent rivers determine the favorable changes in phytoplankton (>nutrients, Chla, a_ph440) and an increment in the number of phytoplankton spectral shapes). Full article

Microalgae are photosynthetic organisms with rapid growth and high biochemical diversity, capable of thriving in a variety of environments. Among them, dinoflagellates, particularly symbiotic species like Durusdinium glynnii, have gained attention due to their potential for biotechnological applications, especially in the production of valuable fatty acids. However, the delicate cultivation of dinoflagellates remains a challenge due to their sensitivity to shear stress and complex morphology. In this study, we evaluated the influence of inoculum percentage (10%, 25%, and 50%) on the growth performance and fatty acid profile of D. glynnii during a scale-up process from test tubes to a pilot-scale photobioreactor. Higher inoculum concentrations (50%) promoted faster acclimatization, higher specific growth rates (µ_max), and greater final biomass densities, optimizing the cultivation process. Meanwhile, lower inoculum concentrations (10%) favored the accumulation of polyunsaturated fatty acids, particularly DHA (C22:6n3), indicating a trade-off between biomass productivity and fatty acid biosynthesis. Overall, D. glynnii demonstrated robust adaptability, reinforcing its potential as a sustainable source of bioactive compounds. Further studies focusing on cellular and metabolic pathways are needed to better elucidate the mechanisms underlying lipid production and growth in this promising species. Full article

Apicortin, a tubulin/microtubule-binding protein, was first described in 2009 as a protein characteristic of apicomplexans; it was found to be present in all Apicomplexa genomes already sequenced. Apart from these, it was found only in Trichoplax adhaerens, the only known representative of Placozoa at the time. Subsequent analyses revealed that it is present in both closely and distantly related taxa of Apicomplexa (Chrompodellids, Squirmids, Dinoflagellates, and Perkinsids, i.e., in Myzozoa). On the other hand, it turned out that it is also present in early-branching fungi that reproduce by zoospores. Now, we have shown that apicortin is found in many deep-branching opisthokonts. In addition to these fungi and T. adhaerens, it is also present in other simple animals, including further Placozoa and Ctenophora, and another opisthokont clade, choanoflagellates. However, apicortin-homologous sequences detected in the genomes/transcriptomes of bilaterian animals are the result of contamination. Full article