Production of Paralytic Shellfish Toxins (PSTs) in Toxic Alexandrium catenella is Intertwined with Photosynthesis and Energy Production

Alexandrium minutum and Alexandrium tamutum are two closely related harmful algal bloom (HAB)-causing species with different toxicity. Using isobaric tags for relative and absolute quantitation (iTRAQ)-based quantitative proteomics and two-dimensional differential gel electrophoresis (2D-DIGE), a comprehensive characterization of the proteomes of A. minutum and A. tamutum was performed to identify the cellular and molecular underpinnings for the dissimilarity between these two species. A total of 1436 proteins and 420 protein spots were identified using iTRAQ-based proteomics and 2D-DIGE, respectively. Both methods revealed little difference (10–12%) between the proteomes of A. minutum and A. tamutum, highlighting that these organisms follow similar cellular and biological processes at the exponential stage. Toxin biosynthetic enzymes were present in both organisms. However, the gonyautoxin-producing A. minutum showed higher levels of osmotic growth proteins, Zn-dependent alcohol dehydrogenase and type-I polyketide synthase compared to the non-toxic A. tamutum. Further, A. tamutum had increased S-adenosylmethionine transferase that may potentially have a negative feedback mechanism to toxin biosynthesis. The complementary proteomics approach provided insights into the biochemistry of these two closely related HAB-causing organisms. The identified proteins are potential biomarkers for organismal toxicity and could be explored for environmental monitoring.

Section: Discussionsupporting

confidence: 92%

Differentiating Two Closely Related Alexandrium Species Using Comparative Quantitative Proteomics

Subong

Lluisma

Azanza

et al. 2020

“…This observation could be further explained by earlier phylogenetic studies that the Karenia species contained a different type of plastid while Gymnodinium and Alexandrium species might have the same type of plastid [ 40 , 41 , 42 ]. Although multiple studies suggested that STX biosynthesis was correlated to photosynthesis and energy production in dinoflagellates [ 43 , 44 , 45 ], whether the FCPs and F-ATPase contributed to STX biosynthesis is still unclear, and further investigation is required.…”

Section: Discussionmentioning

confidence: 99%

Finding Species-Specific Extracellular Surface-Facing Proteomes in Toxic Dinoflagellates

Chan

Kong

Tse

et al. 2021

Self Cite

As a sequel to our previous report of the existence of species-specific protein/peptide expression profiles (PEPs) acquired by mass spectrometry in some dinoflagellates, we established, with the help of a plasma-membrane-impermeable labeling agent, a surface amphiesmal protein extraction method (SAPE) to label and capture species-specific surface proteins (SSSPs) as well as saxitoxins-producing-species-specific surface proteins (Stx-SSPs) that face the extracellular space (i.e., SSSPsEf and Stx-SSPsEf). Five selected toxic dinoflagellates, Alexandrium minutum, A. lusitanicum, A. tamarense, Gymnodinium catenatum, and Karenia mikimotoi, were used in this study. Transcriptomic databases of these five species were also constructed. With the aid of liquid chromatography linked-tandem mass spectrometry (LC-MS/MS) and the transcriptomic databases of these species, extracellularly facing membrane proteomes of the five different species were identified. Within these proteomes, 16 extracellular-facing and functionally significant transport proteins were found. Furthermore, 10 SSSPs and 6 Stx-SSPs were identified as amphiesmal proteins but not facing outward to the extracellular environment. We also found SSSPsEf and Stx-SSPsEf in the proteomes. The potential functional correlation of these proteins towards the production of saxitoxins in dinoflagellates and the degree of species specificity were discussed accordingly.

“…The PST content in the A. catenella strain ACT03 was stable at irradiance ranging from 10 to 70 µmol photons m −2 s −1 , then slightly increased at 130 to 260 µmol photons m −2 s −1 [48]. It was suggested that light availability could affect the toxin biosynthesis of dinoflagellate A. catenella [54]. In this study, shading test showed that MP shading had no significant effect on the average toxin content in each cell of ATHK and the total toxin production (Figure 8 and Table 1), which indicates that MP do not affect the biosynthesis of PST by shading reduced irradiance.…”

Section: Pst Productionmentioning

confidence: 99%

Effects of Polystyrene Microplastics on Growth and Toxin Production of Alexandrium pacificum

Liu

Qiu

Tang

et al. 2021

Microplastics (MP) widely distributed in aquatic environments have adverse effects on aquatic organisms. Currently, the impact of MP on toxigenic red tide microalgae is poorly understood. In this study, the strain of Alexandriumpacificum ATHK, typically producing paralytic shellfish toxins (PST), was selected as the target. Effects of 1 and 0.1 μm polystyrene MP with three concentration gradients (5 mg L−1, 25 mg L−1 and 100 mg L−1) on the growth, chlorophyll a (Chl a), photosynthetic activity (Fv/Fm) and PST production of ATHK were explored. Results showed that the high concentration (100 mg L−1) of 1 μm and 0.1 μm MP significantly inhibited the growth of ATHK, and the inhibition depended on the size and concentration of MP. Contents of Chl a showed an increase with various degrees after MP exposure in all cases. The photosynthesis indicator Fv/Fm of ATHK was significantly inhibited in the first 11 days, then gradually returned to the level of control group at day 13, and finally was gradually inhibited in the 1 μm MP treatments, and promotion or inhibition to some degree also occurred at different periods after exposure to 0.1 μm MP. Overall, both particle sizes of MP at 5 and 25 mg L−1 had no significant effect on cell toxin quota, and the high concentration 100 mg L−1 significantly promoted the PST biosynthesis on the day 7, 11 and 15. No significant difference occurred in the cell toxin quota and the total toxin content in all treatments at the end of the experiment (day 21). All MP treatments did not change the toxin profiles of ATHK, nor did the relative molar percentage of main PST components. The growth of ATHK, Chl a content, Fv/Fm and toxin production were not affected by MP shading. This is the first report on the effects of MP on the PST-producing microalgae, which will improve the understanding of the adverse impact of MP on the growth and toxin production of A. pacificum.