PubMed · 1236969
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R Hirano. 1975. [Red tide].. https://pubmed.ncbi.nlm.nih.gov/1236969/
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Dinoflagellates, a class of unicellular eukaryotic phytoplankton, exhibit minimal transcriptional regulation, representing a unique model for exploring gene expression. The biosynthesis, distribution, regulation, and function of mRNA N1-methyladenosine (m1A) remain controversial due to its limited presence in typical eukaryotic mRNA. This study provides a comprehensive map of m1A in dinoflagellate mRNA and shows that m1A, rather than N6-methyladenosine (m6A), is the most prevalent internal mRNA modification in various dinoflagellate species, with an asymmetric distribution along mature transcripts. In Amphidinium carterae, we identify 6549 m1A sites characterized by a non-tRNA T-loop-like sequence motif within the transcripts of 3196 genes, many of which are involved in regulating carbon and nitrogen metabolism. Enriched within 3'UTRs, dinoflagellate mRNA m1A levels negatively correlate with translation efficiency. Nitrogen depletion further decreases mRNA m1A levels. Our data suggest that distinctive patterns of m1A modification might influence the expression of metabolism-related genes through translational control.
Compartmentalization of specialized functions to discrete locales is a fundamental theme of eucaryotic organization in cells. We report here that bioluminescence of the dinoflagellate alga Gonyaulax originates in vivo from discrete subcellular loci that are intrinsically fluorescent. We demonstrate this localization by comparing the loci of fluorescence and bioluminescence as visualized by image-intensified video microscopy. These fluorescent particles appeared to be the same as the previously described in vitro "scintillons." We attribute the endogenous fluorescence to that of the bioluminescence substrate, luciferin, because (a) the fluorescence excitation and emission characteristics are comparable, (b) the autofluorescence is lost after exhaustive stimulation of bioluminescence, and (c) the fluorescence of discharged particles in vitro can be restored by adding luciferin. The fluorescence in vivo exhibits a standard property of circadian (daily) rhythmicity: under constant environmental conditions, the intensity of the particle fluorescence fluctuates cyclically (it is maximal during the night phase and is low during the day). Thus, luciferin is localized within the cell at discrete loci from which the bioluminescence emanates; the cellular quantity of luciferin is rhythmically modulated by the circadian clock.
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