Proliferation of dinoflagellates: blooming or bleaching

Wong, Joseph T.Y.; Kwok, Alvin Chun Man

doi:10.1002/bies.20250

Cited by 40 publications

(38 citation statements)

References 102 publications

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“…The evolutionary development of LCCs by ancestral alveolates probably involved concomitant loss of the nucleosomal histones and the recruitment of some prokaryotic proteins (46). Nucleosomes impose a burden on the progress of DNA replication (36).…”

Section: Discussionmentioning

confidence: 99%

Birefringence and DNA Condensation of Liquid Crystalline Chromosomes

et al. 2010

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DNA can self-assemble in vitro into several liquid crystalline phases at high concentrations. The largest known genomes are encoded by the cholesteric liquid crystalline chromosomes (LCCs) of the dinoflagellates, a diverse group of protists related to the malarial parasites. Very little is known about how the liquid crystalline packaging strategy is employed to organize these genomes, the largest among living eukaryotes-up to 80 times the size of the human genome. Comparative measurements using a semiautomatic polarizing microscope demonstrated that there is a large variation in the birefringence, an optical property of anisotropic materials, of the chromosomes from different dinoflagellate species, despite their apparently similar ultrastructural patterns of bands and arches. There is a large variation in the chromosomal arrangements in the nuclei and individual karyotypes. Our data suggest that both macroscopic and ultrastructural arrangements affect the apparent birefringence of the liquid crystalline chromosomes. Positive correlations are demonstrated for the first time between the level of absolute retardance and both the DNA content and the observed helical pitch measured from transmission electron microscopy (TEM) photomicrographs. Experiments that induced disassembly of the chromosomes revealed multiple orders of organization in the dinoflagellate chromosomes. With the low protein-to-DNA ratio, we propose that a highly regulated use of entropy-driven force must be involved in the assembly of these LCCs. Knowledge of the mechanism of packaging and arranging these largest known DNAs into different shapes and different formats in the nuclei would be of great value in the use of DNA as nanostructural material.DNA molecules are the indispensable genetic material of every organism. Apart from having the encoding power of a 4-base double-stranded polymer, DNA also has an enormous capacity to be condensed. It is probably this ability that allowed the evolution of increasing genome sizes in the eukaryotes. Histone-mediated nucleosome-based chromatin is the prevailing method for DNA packaging, but it is not the only way that DNA is condensed in the eukaryotes. Highly compact liquid crystalline DNA has been reported in several animal sperm nuclei (11, 28) and was also found in the nucleosomeless liquid crystalline chromosomes (LCCs) of dinoflagellates. Neither animal sperm nuclei nor dinoflagellate nuclei employ histones. In fact, the histone core octamer may hinder the attainment of ultrahigh levels of condensation due to its restrictive volume. In the sperm model, protamine is a sperm-specific DNA-binding protein (ϳ7 kDa) that is an order of magnitude smaller than the histone core octamer, and it adopts a structural role in the organization of the male gametic genome (1, 3). It is this very reduction in the protein-to-DNA ratio that may well enable the high DNA compaction into a liquid crystalline state. The dinoflagellate chromosomes are known to have a proteinto-DNA ratio even smaller than those of the prokaryo...

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Section: Discussionmentioning

confidence: 99%

Birefringence and DNA Condensation of Liquid Crystalline Chromosomes

et al. 2010

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“…This slow growth dynamic makes zooxanthellae particularly well suited to symbiotic relationships (Wong and Kwok, 2005). In its free-living state, zooxanthellae can exist as motile zoospore (Stat et al, 2006).…”

Section: The Coral-algae Symbiosis: Zooxanthellae Cell Proliferationmentioning

confidence: 99%

Breakdown of the coral-algae symbiosis: towards formalising a linkage between warm-water bleaching thresholds and the growth rate of the intracellular zooxanthellae

Wooldridge

2013

Biogeosciences

130

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Impairment of the photosynthetic machinery of the algal endosymbiont ("zooxanthellae") is the proximal driver of the thermal breakdown of the coral-algae symbiosis ("coral bleaching"). Yet, the initial site of damage, and early dynamics of the impairment are still not well resolved. In this perspective essay, I consider further a recent hypothesis which proposes an energetic disruption to the carbon-concentrating mechanisms (CCMs) of the coral host, and the resultant onset of CO₂-limitation within the photosynthetic "dark reactions" as a unifying cellular mechanism. The hypothesis identifies the enhanced retention of photosynthetic carbon for zooxanthellae (re)growth following an initial irradiance-driven expulsion event as a strong contributing cause of the energetic disruption. If true, then it implies that the onset of the bleaching syndrome and setting of upper thermal bleaching limits are emergent attributes of the coral symbiosis that are ultimately underpinned by the characteristic growth profile of the intracellular zooxanthellae; which is known to depend not just on temperature, but also external (seawater) nutrient availability and zooxanthellae genotype. Here, I review this proposed bleaching linkage at a variety of observational scales, and find it to be parsimonious with the available evidence. Future experiments are suggested that can more formally test the linkage. If correct, the new cellular model delivers a valuable new perspective to consider the future prospects of the coral symbiosis in an era of rapid environmental change, including: (i) the underpinning mechanics (and biological significance) of observed changes in resident zooxanthellae genotypes, and (ii) the now crucial importance of reef water quality in co-determining thermal bleaching resistance

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“…Dinoflagellate cell survival has been found to be unaffected by incubation in colchicine (Cho et al, 2011;Wong and Kwok, 2005). We wanted to test this both in Symbiodinium CCMP-830 in culture and in symbiont cells freshly isolated from hosts.…”

Section: Incubation Of Cultured and Freshly Isolated Symbiodinium In mentioning

confidence: 99%

Stress and death of cnidarian host cells play a role in cnidarian bleaching

Paxton

Davy

Weis

2013

Journal of Experimental Biology

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SUMMARYCoral bleaching occurs when there is a breakdown of the symbiosis between cnidarian hosts and resident Symbiodinium spp. Multiple mechanisms for the bleaching process have been identified, including apoptosis and autophagy, and most previous work has focused on the Symbiodinium cell as the initiator of the bleaching cascade. In this work we show that it is possible for host cells to initiate apoptosis that can contribute to death of the Symbiodinium cell. First we found that colchicine, which results in apoptosis in other animals, causes cell death in the model anemone Aiptasia sp. but not in cultured Symbiodinium CCMP-830 cells or in cells freshly isolated from host Aiptasia (at least within the time frame of our study). In contrast, when symbiotic Aiptasia were incubated in colchicine, cell death in the resident Symbiodinium cells was observed, suggesting a host effect on symbiont mortality. Using live-cell confocal imaging of macerated symbiotic host cell isolates, we identified a pattern where the initiation of host cell death was followed by mortality of the resident Symbiodinium cells. This same pattern was observed in symbiotic host cells that were subjected to temperature stress. This research suggests that mortality of symbionts during temperature-induced bleaching can be initiated in part by host cell apoptosis.

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Proliferation of dinoflagellates: blooming or bleaching

Cited by 40 publications

References 102 publications

Birefringence and DNA Condensation of Liquid Crystalline Chromosomes

Birefringence and DNA Condensation of Liquid Crystalline Chromosomes

Breakdown of the coral-algae symbiosis: towards formalising a linkage between warm-water bleaching thresholds and the growth rate of the intracellular zooxanthellae

Stress and death of cnidarian host cells play a role in cnidarian bleaching

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