Dinosporin is a macromolecular, highly resistant organic compound which forms or partly forms, the enclosing wall of fossilizable organic-walled

dinoflagellate cysts Dinocysts or dinoflagellate cysts are typically 15 to 100 µm in diameter and produced by around 15–20% of living dinoflagellates as a dormant, zygotic stage of their lifecycle, which can accumulate in the sediments as microfossils. Organic- ...

Composition

The walls of organic-walled

dinocysts Dinocysts or dinoflagellate cysts are typically 15 to 100 µm in diameter and produced by around 15–20% of living dinoflagellates as a dormant, zygotic stage of their lifecycle, which can accumulate in the sediments as microfossils. Organic- ...

are composed of the resistant biopolymer called dinosporin. This organic compound has similarities to

sporopollenin 270px, SEM image of pollen grains Sporopollenin is one of the most chemically inert biological polymers. It is a major component of the tough outer (exine) walls of plant spores and pollen grains. It is chemically very stable and is usually well ...

, but is unique to

dinoflagellates The dinoflagellates (Greek δῖνος ''dinos'' "whirling" and Latin ''flagellum'' "whip, scourge") are a monophyletic group of single-celled eukaryotes constituting the phylum Dinoflagellata and are usually considered algae. Dinoflagellates are ...

. Resistant biopolymers are non-hydrolyzable and fossilizable macromolecular organic compounds present in many microalgal cell walls and fossil palynomorphs. Thus far, only the motile stage of ''Gymnodinium catenatum'' has been shown to produce the highly aliphatic biopolymer

algaenan Algaenan is the resistant biopolymer in the cell walls of unrelated groups of green algae, and facilitates their preservation in the fossil record A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any on ...

. Dinosporin has been shown to be a significantly different biopolymer from algaenan, which demonstrates that dinoflagellates are able to produce a completely different biomacromolecule for their resting cysts. Previous descriptions of dinosporin having similar properties to sporopollenin were based on both compounds’ resistance to hydrolysis and high preservation potential. However, further research has instead shown that dinosporin is compositionally distinct. Despite the clear distinction between dinosporin and other resistant biopolymer groups, very little is known about the actual structure of dinosporin. A recent study has suggested that dinosporin present in cysts of ''Lingulodinium polyedrum'' does not contain significant amounts of long chain aliphatics, nor is it primarily aromatic, but that it is a highly crosslinked carbohydrate-based polymer. Furthermore, dinosporin may be taxon specific as species within the same genus exhibited different compositions, so that dinosporin may be more accurately thought of as a suite of related but chemically distinguishable biopolymers. Studies of dinosporin composition and structure are complicated by the fact that the cysts have to either have the cell contents effectively removed (cysts generated in culture) or be individually picked (cysts from sediments) in order to ensure sample purity. The culture-derived cysts risk condensation of the cell content and modification of the cyst wall while the cysts picked from sediment are time consuming to acquire and may have been altered by post-mortem processes. For example, the macromolecular composition of the fossil dinoflagellate cyst ''Thalassiphora pelagica'' was analyzed, but post-mortem alteration was noted. Furthermore, dinocysts can be subject to selective preservation . This has been speculated to reflect different dinosporin compositions in various dinocyst lineages, but so far, no conclusive differences have been shown. Recent

Fourier-transform infrared spectroscopy Fourier-transform infrared spectroscopy (FTIR) is a technique used to obtain an infrared spectrum of absorption or emission of a solid, liquid, or gas. An FTIR spectrometer simultaneously collects high-resolution spectral data over a wide spectra ...

(FTIR) work shows both differences and similarities between the major dinocyst lineages, which are suggested to be related to nutritional strategies.Bogus, K. Mertens, K.N., Lauwaert, J., Harding, I.C., Vrielinck, H., Zonneveld, K.A.F., Versteegh, G.J.M. (2014). Variations in the chemical composition of organic-walled dinoflagellate resting cysts produced by phototrophic and heterotrophic dinoflagellates. Journal of Phycology doi: 10.1111/jpy.12170.

References

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Composition

References

Further reading