Cold-Induced Cysts of the Photosynthetic DinoflagellateLingulodinium polyedrumHave an Arrested Circadian Bioluminescence Rhythm and Lower Levels of Protein Phosphorylation    

Abstract

Dinoflagellates are microscopic, eukaryotic, and primarily marine plankton. Temporary cyst formation is a well-known physiological response of dinoflagellate cells to environmental stresses. However, the molecular underpinnings of cold-induced cyst physiology have never been described. Cultures of the photosynthetic dinoflagellate Lingulodinium polyedrum readily form temporary cysts when placed at low (8°C 6 1°C) temperature and excyst to form normal motile cells following a return to normal temperature (18°C 6 1°C). The normal circadian bioluminescence rhythm and the expected changes in Luciferin Binding Protein abundance were arrested in L. polyedrum cysts. Furthermore, after excystment, the bioluminescence rhythm initiates at a time corresponding to zeitgeber 12, independent of the time when the cells encysted. Phosphoprotein staining after two-dimensional polyacrylamide gel electrophoresis, as well as column-based phosphoprotein enrichment followed by liquid chromatography tandem mass spectrometry, showed cyst proteins are hypophosphorylated when compared with those from motile cells, with the most marked decreases found for predicted Casein Kinase2 target sites. In contrast to the phosphoproteome, the cyst proteome is not markedly different from motile cells, as assessed by two-dimensional polyacrylamide gel electrophoresis. In addition to changes in the phosphoproteome, RNA sequencing revealed that cysts show a significant decrease in the levels of 132 RNAs. Of the 42 RNAs that were identified by sequence analysis, 21 correspond to plastid-encoded gene products and 11 to nuclear-encoded cell wall/plasma membrane components. Our data are consistent with a model in which the highly reduced metabolism in cysts is achieved primarily by alterations in the phosphoproteome. The stalling of the circadian rhythm suggests temporary cysts may provide an interesting model to address the circadian system of dinoflagellates.

miRNAs Do Not Regulate Circadian Protein Synthesis in the Dinoflagellate Lingulodinium polyedrum

“…polyedrum , we next tested if the Argonaute and Dicer proteins required for miRNA synthesis were present in the transcriptome. We performed tBLASTn searches of our Velvet [30] and Trinity [39] assemblies using different domains selected from the Argonaute and Dicer sequences of S . microadriaticum [19].…”

Low temperature nullifies the circadian clock in cyanobacteria through Hopf bifurcation

“…Further, circadian rhythms can be nullified at low-temperature conditions in numerous poikilotherms and plants. For example, circadian rhythms are undetectable at 11.5°C in the marine dinoflagellate Lingulodnium polyedrum (formerly known as Ganyaulax) (1)(2)(3), at 17°C in the roach Leucophaea (4), at 20°C in Drosophila (5), at 10.5°C in the filamentous fungus Neurospora (6), at 12°C in the duckweed Lemna gibba (7), and at 4°C in the tomato Lycopersicon esculentum Mill (8), the European chestnuts Castanea sativa (9), and Arabidopsis (10). The loss of physiological rhythmicity that occurs in plants is reflected by global gene expression levels (10).…”

Cloning and Partial Characterization of a Cold Shock Domain‐Containing Protein Gene from the Dinoflagellate Scrippsiella trochoidea

“…Although there was no evidence for an increase in CSP protein abundance on 2D PAGE in cold‐induced temporary cysts of L. polyedrum (Roy et al. ), we did observe elevated expressions of two genes of CSPs in resting cysts of Scrippsiella trochoidea (Deng et al. ).…”

“…; Roy et al. ). CSPs are reported to be the most abundant putative transcription factors in the transcriptomes of dinoflagellates Symbiodinium spp.…”

“…; Roy et al. ). However, until now, gaps remained in our understandings about what physiological processes in which CSPs are involved and what roles CSPs play in these processes.…”