Tag: dinoflagellates

Related Articles

Unique nucleocytoplasmic dsDNA and +ssRNA viruses are associated with the dinoflagellate endosymbionts of corals.

ISME J. 2013 Jan;7(1):13-27

Authors: Correa AM, Welsh RM, Vega Thurber RL

Abstract
The residence of dinoflagellate algae (genus: Symbiodinium) within scleractinian corals is critical to the construction and persistence of tropical reefs. In recent decades, however, acute and chronic environmental stressors have frequently destabilized this symbiosis, ultimately leading to coral mortality and reef decline. Viral infection has been suggested as a trigger of coral-Symbiodinium dissociation; knowledge of the diversity and hosts of coral-associated viruses is critical to evaluating this hypothesis. Here, we present the first genomic evidence of viruses associated with Symbiodinium, based on the presence of transcribed +ss (single-stranded) RNA and ds (double-stranded) DNA virus-like genes in complementary DNA viromes of the coral Montastraea cavernosa and expressed sequence tag (EST) libraries generated from Symbiodinium cultures. The M. cavernosa viromes contained divergent viral sequences similar to the major capsid protein of the dinoflagellate-infecting +ssRNA Heterocapsa circularisquama virus, suggesting a highly novel dinornavirus could infect Symbiodinium. Further, similarities to dsDNA viruses dominated (∼69%) eukaryotic viral similarities in the M. cavernosa viromes. Transcripts highly similar to eukaryotic algae-infecting phycodnaviruses were identified in the viromes, and homologs to these sequences were found in two independently generated Symbiodinium EST libraries. Phylogenetic reconstructions substantiate that these transcripts are undescribed and distinct members of the nucleocytoplasmic large DNA virus (NCLDVs) group. Based on a preponderance of evidence, we infer that the novel NCLDVs and RNA virus described here are associated with the algal endosymbionts of corals. If such viruses disrupt Symbiodinium, they are likely to impact the flexibility and/or stability of coral-algal symbioses, and thus long-term reef health and resilience.

PMID: 22791238 [PubMed – in process]

Related Articles
The repertoire of chemical defense genes in the coral Acropora digitifera genome.
Zoolog Sci. 2012 Aug;29(8):510-7
Authors: Shinzato C, Hamada M, Shoguchi E, Kawashima T, Satoh N
Abstract
Scle…

Related Articles
Tertiary endosymbiosis in two dinotoms has generated little change in the mitochondrial genomes of their dinoflagellate hosts and diatom endosymbionts.
PLoS One. 2012;7(8):e43763
Authors: Imanian B, Pombert…

Related Articles
Study of cnidarian-algal symbiosis in the “omics” age.
Biol Bull. 2012 Aug;223(1):44-65
Authors: Meyer E, Weis VM
Abstract
The symbiotic associations between cnidarians and dinoflagellate alg…

Related Articles

The Complex NOD-Like Receptor Repertoire of the Coral Acropora digitifera Includes Novel Domain Combinations.

Mol Biol Evol. 2013 Jan;30(1):167-76

Authors: Hamada M, Shoguchi E, Shinzato C, Kawashima T, Miller DJ, Satoh N

Abstract
Innate immunity in corals is of special interest not only in the context of self-defense but also in relation to the establishment and collapse of their obligate symbiosis with dinoflagellates of the genus Symbiodinium. In innate immunity system of vertebrates, approximately 20 tripartite nucleotide oligomerization domain (NOD)-like receptor proteins that are defined by the presence of a NAIP, CIIA, HET-E and TP1 (NACHT) domain, a C-terminal leucine-rich repeat (LRR) domain, and one of three types of N-terminal effector domain, are known to function as the primary intracellular pattern recognition molecules. Surveying the coral genome revealed not only a larger number of NACHT- and related domain nucleotide-binding adaptor shared by APAF-1, R proteins, and CED-4 (NB-ARC)-encoding loci (∼500) than in other metazoans but also surprising diversity of domain combinations among the coral NACHT/NB-ARC-containing proteins; N-terminal effector domains included the apoptosis-related domains caspase recruitment domain (CARD), death effector domain (DED), and Death, and C-terminal repeat domains included LRRs, tetratricopeptide repeats, ankyrin repeats, and WD40 repeats. Many of the predicted coral proteins that contain a NACHT/NB-ARC domain also contain a glycosyl transferase group 1 domain, a novel domain combination first found in metazoans. Phylogenetic analyses suggest that the NACHT/NB-ARC domain inventories of various metazoan lineages, including corals, are largely products of lineage-specific expansions. Many of the NACHT/NB-ARC loci are organized in pairs or triplets in the Acropora genome, suggesting that the large coral NACHT/NB-ARC repertoire has been generated at least in part by tandem duplication. In addition, shuffling of N-terminal effector domains may have occurred after expansions of specific NACHT/NB-ARC-repeat domain types. These results illustrate the extraordinary complexity of the innate immune repertoire of corals, which may in part reflect adaptive evolution to a symbiotic lifestyle in a uniquely complex and challenging environment.

PMID: 22936719 [PubMed – in process]

Related Articles
Dinoflagellate tandem array gene transcripts are highly conserved and not polycistronic.
Proc Natl Acad Sci U S A. 2012 Sep 25;109(39):15793-8
Authors: Beauchemin M, Roy S, Daoust P, Dagenais-Bellefeuille S,…

Related Articles
ANALYSIS OF ALEXANDRIUM TAMARENSE (DINOPHYCEAE) GENES REVEALS THE COMPLEX EVOLUTIONARY HISTORY OF A MICROBIAL EUKARYOTE().
J Phycol. 2012 Oct 1;48(5):1130-1142
Authors: Chan CX, Soares MB, Bonaldo MF, Wisecav…

Related Articles
Establishment of a Bacterial Expression System and Immunoassay Platform for the Major Capsid Protein of HcRNAV, a Dinoflagellate-Infecting RNA Virus.
Microbes Environ. 2012 Dec 7;27(4):483-9
Authors: Wada K,…

Counterion-mediated decompaction of liquid crystalline chromosomes.

DNA Cell Biol. 2012 Dec;31(12):1657-64

Authors: Sun S, Wong JT, Liu M, Dong F

Abstract
Liquid crystalline phases of DNA and nucleosome core particles can be formed in vitro, indicating the crucial roles of these phases in the maintenance and compaction of genomes in vivo. In the present study, sequential levels of liquid crystalline decompaction were identified in highly purified nuclei of Karenia papilionacea in response to the gradual chelation of divalent counterions by ethylenediaminetetraacetic acid (EDTA); the decompaction was observed using polarizing light microscopy, confocal laser scanning microscopy, and transmission electron microscopy and further confirmed utilizing microcalorimetry. Nested fibrous coils in 150 nm arc-like bands of chromatin were observed in the early stages of chromosomal decompaction. The microcalorimetry spectra of isolated nuclei revealed that the dynamic processes of nuclear decompaction occurred in a nonlinear manner; in addition, an EDTA-sensitive thermal transition between 60°C-70°C, corresponding to a liquid-crystalline-phase transition of chromosomes, was found. The results suggested that nested coils of fibrous chromatin filaments are responsible for the establishment and stabilization of the liquid crystalline and birefringence features of the chromosomes of dinoflagellates. The results also indicated that positively charged divalent counterions play significant roles in modulating liquid crystalline phases to compact the chromosomes of dinoflagellates.

PMID: 23072628 [PubMed – in process]

Related Articles

Loss of nucleosomal DNA condensation coincides with appearance of a novel nuclear protein in dinoflagellates.

Curr Biol. 2012 Dec 18;22(24):2303-12

Authors: Gornik SG, Ford KL, Mulhern TD, Bacic A, McFadden GI, Waller RF

Abstract
BACKGROUND: The packaging, expression, and maintenance of nuclear genomes using histone proteins is a ubiquitous and fundamental feature of eukaryotic cells, yet the phylum Dinoflagellata has apparently abandoned this model of nuclear organization. Their nuclei contain permanently condensed, liquid crystalline chromosomes that seemingly lack histone proteins, and contain remarkably large genomes. The molecular basis for this reorganization is poorly understood, as is the sequence of evolutionary events that led to such radical change. We have investigated nuclear organization in the closest relative to dinoflagellates, Perkinsus marinus, and an early-branching dinoflagellate, Hematodinium sp., to identify early changes that occurred during dinoflagellate nuclear evolution.
RESULTS: We show that P. marinus has a typical nuclear organization that is based on the four core histones. By the early divergence of Hematodinium sp., however, dinoflagellate genome size is dramatically enlarged, chromosomes are permanently condensed, and histones are scarcely detectable. In place of histones, we identify a novel, dominant family of nuclear proteins that is only found in dinoflagellates and, surprisingly, in a family of large algal viruses, the Phycodnaviridae. These new proteins, which we call DVNPs (dinoflagellate/viral nucleoproteins), are highly basic, bind DNA with similar affinity to histones, and occur in multiple posttranslationally modified forms. We find these proteins throughout all dinoflagellates, including early- and late-branching taxa, but not in P. marinus.
CONCLUSIONS: Gain of a major novel family of nucleoproteins, apparently from an algal virus, occurred early in dinoflagellate evolution and coincides with rapid and dramatic reorganization of the dinoflagellate nucleus.

PMID: 23159597 [PubMed – in process]