Detection of endogenous BMAA in dinoflagellate ...

Jiang et al. 2014 PubRaw Science 2:XX-XX

Research Article

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Open Access

Detection of endogenous BMAA in dinoflagellate (Heterocapsa triquetra) hints at evolutionary conservation and environmental concern Liying Jiang1, Leopold L. Ilag1* 1

Department of Analytical Chemistry, Stockholm University, SE-10691 Stockholm, Sweden. Fax: +46 (0) 8156391; Tel: +46 (0) 8 162435 *Corresponding authors, E-mail: [email protected] Received : 2014-02-13 ; Accepted :2014-02-17 ; Online published :2014-02-18 ;Printed :2014-XX-XX

Abstract: BMAA is a non-protein amino acid that has been implicated in neurodegenerative diseases and recently reported to be mis-incorporated into proteins. As a free amino acid it has established toxic effects and recent studies have shown it to be present in the human food chain. The production of this amino acid was initially thought to be exclusive to cyanobacteria but a recent study reported it can also be produced by a eukaryotic organism namely diatoms. In evolutionary terms it is interesting to see if BMAA is produced by more primitive eukaryotes. Dinoflagellates are eukaryotes that emerged 300 million years before Diatoms appeared in fossil records. In this report we establish that axenic cultures of dinoflagellate (Heterocapsa triquetra) do in fact produce BMAA, pointing to the evolutionary conservation of BMAA and indicating it may be an essential metabolite which to date has an unknown natural function. Because dinoflagellates have a complex evolutionary history, mapping a metabolite such as BMAA in various species and related organisms especially in the context of plastid evolution is of significant interest. Keywords: Dinoflagellates, Diatoms, Cyanobacteria, β-N-methylamino-L-alanine (BMAA), neurodegenerative diseases, amyotrophic lateral sclerosis (ALS)

Introduction First detected in cyanobacteria, BMAA is a non-protein amino acid associated with neurodegenerative diseases particularly ALS. It has been reported (1, 2) that BMAA can be mis-incorporated into proteins that can be a means by which misfolded proteins are generated leading to neurodegeneration. Bioincorproation has been suggested earlier (3) but to date no direct evidence for actual BMAA insertion into proteins has been established.

Recently it has been shown that it is not exclusively produced by primitive prokaryotes cyanobacteria but surprisingly also by eukaryotic diatoms (4). The same study indicated that they may present in dinoflagellates but that needs further investigation to be conclusive. Dinoflagellates are unicellular eukaryotes that thrive in both marine and freshwater habitats. About half of the known species are capable of photosynthesis thus carrying lightharvesting pigments. They are notoriously


known for toxic blooms that are devastating to aquatic life and pose health risks for humans although only a fraction of all existing species produce toxins. Dinoflagellates appeared about 400 million years ago whereas Diatoms only surfaced around 300 million years later. These two organisms are both ubiquitous and capable of efficiently adapting to environmental fluctuations e.g. in nitrogen availability and share means of coping for example by symbiosis. However, dinoflagellates have the additional faculty of vertical migration and mixotrophy (5). Both dinoflagellates and diatoms have known associations with cyanobacteria. Dinoflagellates are of interest also in nutraceutical production. Method The dinoflagellate (Heterocapsa triquetra) was obtained from Ulla Rasmussen, Stockholm University. The culture condition, sample preparation and UHPLC-MS/MS analysis were performed using same protocol as described previously (4). BMAA and its three isomers, i.e., BAMA, AEG and DAB were unambiguously distinguished by using three criteria: chromatographic retention time, one general SRM transition (459.18>119.08) and three diagnostic SRM transitions (459.18>258.09 for BMAA and BAMA, 459.18>188.08 for DAB, and 459.18>214.10 for AEG), and peak area ratio (within a certain variation) between the general and diagnostic transitions (Fig. 1) (6, 7). Results Two collections were obtained from the axenic culture of Heterocapsa triquetra in March and July of 2012 (See Fig. 2 and 3 respectively). One of them, i.e. the collection in March was reanalyzed in October of 2012 (See Fig. 4). BMAA and AEG were detected in all of them, DAB was detected in the collection from July of 2012, while no BAMA was observed in any of them. All research data is obtained in the Department of Analytical Chemistry in Stockholm University.


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Discussion Genetic studies are powerful means by which one can trace evolutionary history. However it is not easy to determine which genes are functional and active, and which ones are relics. In this regard expressions of protein markers are of significant importance although these may not directly indicate activity as some proteins may have multiple functions through evolution. Metabolites on the other hand are products of active metabolisms that indicate functional pathways. Nevertheless there are several metabolites with unknown functions. It is of evolutionary interest to identify a metabolite such as BMAA that is shared across domains by cyanobacteria and eukaryotic dinoflagellates and diatoms which belong to distinct phyla namely Alveolata and Heterokontophyta, respectively. It is tempting to speculate that this apparent conservation of a metabolite is linked to plastid evolution. It is believed that plastids of eukaryotes arose through endosymbiosis of primitive cyanobacteria. Subsequently, diatoms and dinoflagellates are believed to have derived plastids from a common ancestral red algae (8). They share plastids of more than two membranes and both share pigments chl a and c. Zhang et. al. (9) using 3-gene phylogeny indicated that the dinoflagellate genus Heterocapsa sits in a basal position which is not entirely inconsistent with morphological and paleontological data. Finding BMAA in this primitive dinoflagellate which posses primitive traits may indicate that BMAA occurrence is shared by many other dinoflagellates. Mapping BMAA presence in more species of diatoms and dinoflagellates and matching this with known trees of plastid evolution should prove to be a fruitful exercise although considering the complexity of plastid acquisition (and loss) this may prove to be a challenging task. Subsequent endosymbiosis of a pennate diatom by dinoflagellates as in representatives of the genus Peridinium (10) has been reported. This begs the


question whether BMAA occurrence in diatoms existed before or after such events. It is interesting to consider that acquisition of BMAA biochemistry by diatoms could have also occurred via this route. Indeed there are pennate diatoms that produce BMAA although more of the centric ones were reported to produce it (4). Why eukaryotes such as dinoflagellates and diatoms would produce BMAA is an important issue to unravel as no natural biological function has been ascribed to this non-protein amino acid. Clearly a more taxonomically informed analyses of BMAA presence in more organisms is needed to resolve this question. This can help narrow down determining the natural function of this metabolite. In cyanobacteria, Downing et. al. (11) has suggested that BMAA is either a result of catabolism to provide nitrogen or that BMAA synthesis is a reaction to the lack of nitrogen in the environment. Because of the known symbiosis of diatoms (and dinoflagellates) with cyanobacteria, it is not far-fetched to suppose that cyanobacteria can fix nitrogen which can perhaps be stored by Diatoms and utilised under low nitrogen conditions. Indeed recently, Foster et. al. (12) using mass spectrometry (NanoSIMS) provided the first experimental evidence whereby field symbiotic diatoms acquire fixed nitrogen from cyanobacterial symbionts. Symbiosis of some dinoflagellates with cyanobacteria allows the latter to occupy anaerobic microenvironments within dinoflagellates enhancing the ability to fix nitrogen (13). Analogously, heterocyst formation by cyanobacteria provides anaerobic nests conducive to expression of nitrogenase precisely for nitrogen fixation by these organisms. This involves decrease in pigmentation which has been correlated with nutrient depletion as has been reported (14). It is possible that BMAA is a barometer for nitrogen levels which functions partly to signal nitrogen fixation by cyanobacteria for itself and its symbionts. Sensing of BMAA for


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signalling, as no known specific transporters have been described, could be through use of channels conveying other amino acids. A possible mechanism may simply be through diffusion or through mechanical dissociation of e.g. filamentous forms. At any rate a more systematic study to untangle confounding factors to elucidate the natural role of BMAA is obviously essential. Production of BMAA by dinoflagellates is of important public interest because dinoflagellates are fed upon by molluscs, such as mussels which find its way directly in the human food chain or indirectly as part of feeds for livestock and also because they are becoming an important source of nutraceuticals e.g. docosahexanoic acids (15). Although dinoflagellates are less abundant than diatoms and cyanobacteria, they are ecologically important primary producers. Conclusion BMAA production by Dinoflagellate Heterocapsa truieuerta bridges the evolutionary line from cyanobacteria through to diatoms hinting at a potential conservation of BMAA perhaps linked to plastid evolution that may help unravel the natural role of this non-protein amino acid. Abbreviations BMAA: β-N-methylamino-L-alanine; ALS: amyotrophic lateral sclerosis; UHPLCMS/MS: ultra-high performance liquid chromatography-tandem mass spectrometry; BAMA: β-amino-N-methylalanine; AEG; N-(2-aminoethyl) glycine; DAB: 2, 4-diaminobutyric acid; SRM: selected-reaction monitoring; NanoSIMS: nanometer scale secondary ion mass spectrometry. Author contribution LLI conceptualised the context of the study. LJ obtained the data. LLI and LJ wrote the manuscript.


Acknowledgement We would like to thank Ulla Rasmussen for cultures of Heterocapsa triquetra. Duality of Interest LJ and her husband are major share holders of the Raw Publishing and Research Limited. LJ’s husband is the editor. Authors are neither charged nor paid by the publisher. Reference 1. O. Karlsson, L. Jiang, L. L. Ilag, M. Andersson, E. B. Brittebo, Protein association of the neurotoxin and non-protein amino acid BMAA (β-Nmethylamino-l-alanine) in the liver and brain following neonatal administration in rats. Toxicol Lett. (2014). 2. R. A. Dunlop, P. A. Cox, S. A. Banack, K. J. Rodgers, The Non-Protein Amino Acid BMAA Is Misincorporated into Human Proteins in Place of lSerine Causing Protein Misfolding and Aggregation. PloS One. 8, e75376 (2013). 3. O. Karlsson, C. Berg, E. B. Brittebo, N. G. Lindquist, Retention of the cyanobacterial neurotoxin β-N-methylamino-l-alanine in melanin and neuromelanin-containing cells–a possible link between Parkinson-dementia complex and pigmentary retinopathy. Pigment Cell & Melanoma Research. 22, 120-130 (2009). 4. L. Jiang et al., Diatoms: A Novel Source for the Neurotoxin BMAA in Aquatic Environments. PLoS One. 9, e84578 (2014). 5. S. Dagenais-Bellefeuille, D. Morse, Putting the N in dinoflagellates. Frontiers in Microbiology. 4 (2013). 6. L. Jiang, B. Aigret, W. M. De Borggraeve, Z. Spacil, L. L. Ilag, Selective LC-MS/MS method for the identification of BMAA from its isomers in biological samples. Anal. Bioanal. Chem. 403, 1719-1730 (2012).


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7. L. Jiang, E. Johnston, K. M. Aaberg, U. Nilsson, L. L. Ilag, Strategy for quantifying trace levels of BMAA in cyanobacteria by LC/MS/MS. Anal. Bioanal. Chem. 405, 1283-1292 (2013). 8. J. Janouskovec, A. Horak, M. Obornik, J. Lukes, P. J. Keeling, A common red algal origin of the apicomplexan, dinoflagellate, and heterokont plastids. Proc. Natl. Acad. Sci. U. S. A. 107, 1094910954 (2010). 9. H. Zhang, D. Bhattacharya, S. Lin, A three-gene dinoflagellate phylogeny suggests monophyly of prorocentrales and a basal position for Amphidinium and Heterocapsa. J. Mol. Evol. 65, 463-474 (2007). 10. Y. Inagaki, J. B. Dacks, W. F. Doolittle, K. I. Watanabe, T. Ohama, Evolutionary relationship between dinoflagellates bearing obligate diatom endosymbionts: insight into tertiary endosymbiosis. Int. J. Syst. Evol. Microbiol. 50 Pt 6, 2075-2081 (2000). 11. S. Downing, S. Banack, J. Metcalf, P. Cox, T. Downing, Nitrogen starvation of cyanobacteria results in the production of β-N-methylamino-Lalanine. Toxicon. 58, 187-194 (2011). 12. R. A. Foster et al., Nitrogen fixation and transfer in open ocean diatom–cyanobacterial symbioses. The ISME Journal. 5, 1484-1493 (2011). 13. N. Gordon, D. Angel, A. Neori, N. Kress, B. Kimor, Heterotrophic dinoflagellates with symbiotic Cyanobacteria and nitrogen limitation in the Gulf-of-Aqaba. Mar. Ecol. Prog. Ser. 107, 8388 (1994). 14. S. Downing, M. van de Venter, T. G. Downing, The effect of exogenous β-N-methylamino-Lalanine on the growth of Synechocystis PCC6803. Microb. Ecol. 63, 149-156 (2012). 15. A. Mendes, A. Reis, R. Vasconcelos, P. Guerra, T. L. da Silva, Crypthecodinium cohnii with emphasis on DHA production: a review. J. Appl. Phycol. 21, 199-214 (2009).

http://www.pubraw.com This is an Open Access article which permits unrestricted use in any medium given that the original source is appropriately cited. Please cite this article as: Jiang, L. and Ilag, L.L. (2014). Detection of endogenous BMAA in dinoflagellate (Heterocapsa triquetra) hints at evolutionary conservation and environmental concern. PubRaw Science 2，1-8.



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Fig. 1: LC-MS/MS chromatogram of BMAA and its three isomers (400 ng/ml x 10 μl for DAB and 100 ng/ml x 10 μl for others before AQC derivatization, RT and AA stand for retention time and automatically measured peak area, respectively.). The peaks corresponding to BAMA were marked with ∆ (RT = 6.35 min for its general transition 459.18>119.08 and its diagnostic transition 459.18>258.09); The peaks corresponding to BMAA were marked with * (RT = 8.18 min for its general transition 459.18>119.08 and RT = 8.16 min for its diagnostic transition 459.18>258.09); The peaks corresponding to AEG were marked with ** (Retention time for its general transition 459.18>119.08 is not shown and RT = 8.60 min for its diagnostic transition 459.18>214.10); The peaks corresponding to DAB were marked with * * * (RT = 9.16 min for its general transition 459.18>119.08 and its diagnostic transition 459.18>188.08).



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Fig. 2: LC-MS/MS chromatogram of one axenic culture collection of Heterocapsa triquetra analyzed in March of 2012. The peaks corresponding to BMAA were marked with * (RT = 8.06 min for its general transition 459.18>119.08 and RT = 8.08 min for its diagnostic transition 459.18>258.09); The peaks corresponding to AEG were marked with ** (RT = 8.53 for its general transition 459.18>119.08 and RT = 8.58 min for its diagnostic transition 459.18>214.10).



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Fig. 3: LC-MS/MS chromatogram of another axenic culture collection of Heterocapsa triquetra analyzed in July of 2012. The peaks corresponding to BMAA were marked with * (RT = 8.29 min for its general transition 459.18>119.08 and RT = 8.26 min for its diagnostic transition 459.18>258.09, The peak height was relatively diminished due to the height of adjacent peak of AEG.); The peaks corresponding to AEG were marked with ** (RT = 8.75 min for its general transition 459.18>119.08 and its diagnostic transition 459.18>214.10); The peaks corresponding to DAB were marked with * * * (RT = 9.33 min for its general transition 459.18>119.08 and its diagnostic transition 459.18>188.08).



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Fig. 4: LC-MS/MS chromatogram of the axenic culture collection of Heterocapsa triquetra that was initially analyzed in July of 2012 and analyzed again in October of 2012. The peaks corresponding to BMAA were marked with * (RT = 9.07 min for its general transition 459.18>119.08 and its diagnostic transition 459.18>258.09); The peaks corresponding to AEG were marked with ** (RT = 9.58 for its general transition 459.18>119.08 and RT = 9.57 min for its diagnostic transition 459.18>214.10).