Genetic analyses of Dinophysis spp. support kleptoplastidy

Minnhagen, Susanna; Janson, Sven

doi:10.1111/j.1574-6941.2006.00096.x

Cited by 49 publications

(69 citation statements)

References 28 publications

(54 reference statements)

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“…may derive from a cryptophyte, or an organism with a cryptophyte endosymbiont (Schnepf & Elbrächter 1988). Molecular data support this idea, since the 16 rRNA and psbA genes of D. acuminata and the cryptophyte Teleaulax amphioxia have been found to be alike (Janson & Granéli 2003, Janson 2004, Minnhagen & Janson 2006. However, since Dinophysis spp.…”

Section: Introductionmentioning

confidence: 63%

Role of food uptake for photosynthesis, growth and survival of the mixotrophic dinoflagellate Dinophysis acuminata

Riisgaard¹,

Hansen²

2009

Mar. Ecol. Prog. Ser.

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Dinophysis acuminata is a mixotrophic dinoflagellate frequently causing diarrhetic shellfish poisoning. D. acuminata was isolated from Danish coastal waters and cultivated using the mixotrophic ciliate Mesodinium rubrum as prey. The roles of food uptake and photosynthesis for the growth and survival of D. acuminata were studied. The observed maximum growth rate was ca. 0.45 d -1 at an irradiance of 100 µmol photons m -2 s -1 when supplied with well-fed M. rubrum at concentrations >1000 M. rubrum ml . Apart from the importance of prey concentration, data revealed that ingestion and growth of D. acuminata are, to a certain degree, dependent on the growth rate of its ciliate prey. Photosynthesis was studied in a culture of D. acuminata, initially grown at prey saturation (>1000 M. rubrum cells ml -1) and subsequently allowed to deplete the prey. When the ciliate prey was added, the photosynthetic rate of D. acuminata increased from about 7 to 38 pg C cell -1 h -1 within the first 2 d. When subsequently subjected to starvation, the photosynthetic activity rapidly decreased to a pre-feeding level, and, without a minimum food uptake, D. acuminata was not able to maintain photosynthetic growth. At high prey concentrations, 70 to 90% of the gross C uptake can be explained by food uptake. However, at low prey concentrations, only 0 to 55% of the gross C uptake is likely to be derived from food uptake. The data indicate that in natural environments, D. acuminata may often be food limited, and, in this situation, photosynthesis may not only be a supplement to the basic nutrition, but rather the primary C source.KEY WORDS: Dinophysis acuminata · Dinoflagellate · Mixotrophy · Photosynthesis · Growth · Survival · Mesodinium rubrumResale or republication not permitted without written consent of the publisher

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Section: Introductionmentioning

confidence: 63%

Role of food uptake for photosynthesis, growth and survival of the mixotrophic dinoflagellate Dinophysis acuminata

Riisgaard¹,

Hansen²

2009

Mar. Ecol. Prog. Ser.

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“…An endosymbiosis is considered to be stable if there is genetic integration of the endosymbiont and host, meaning transfer of essential endosymbiont genes to the host nucleus and protein retargeting (Bhattacharya et al 2007). For example, Dinophysis has long been considered to have a cryptophyte endosymbiont chloroplast, but the latter was very recently found to have been acquired through kleptoplastidy (Koike et al 2005;Minnhagen and Janson 2006;Takishita et al 2002).…”

Section: Introductionmentioning

confidence: 99%

The Life History and Cell Cycle of Kryptoperidinium foliaceum, A Dinoflagellate with Two Eukaryotic Nuclei

Figueroa

Bravo

Fraga

et al. 2009

Protist

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Kryptoperidinium foliaceum is a binucleate dinoflagellate that contains an endosymbiont nucleus of diatom origin. However, it is unknown whether the binucleate condition is permanent or not and how the diatom nucleus behaves during the life history processes. In this sense, it is also unknown if there is a sexual cycle or a resting stage during the life history of this species, two key aspects necessary to understand the life history strategy of this dinoflagellate. To answer these questions, life history and cell cycle studies were performed with the following results: (i) Kryptoperidinium foliaceum has a sexual cycle and in the dinoflagellate strains studied, the binucleate condition is permanent. Sexuality in the host was confirmed by the presence of fusing gamete pairs and planozygotes in clonal cultures (revealing homothallism), but signs of meiosis in the endosymbiont were not observed. The endosymbiont nucleus likely fuses first, because fusing gamete pairs were found to have two dinoflagellate nuclei but only one endosymbiont nucleus. After complete gamete fusion, the planozygotes had apparently normal endosymbiont and dinoflagellate nuclei. (ii) Asexual division studies using flow cytometry showed that the S phase in the endosymbiont (diatom) nucleus starts 6-8 h later than in the host nucleus, but there was no evidence of mitosis in the former. (iii) Sexual and asexual cysts were formed in culture. Neither cysts from natural samples nor those formed in culture exhibited a dormancy period before germination.

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“…The idea that photosynthesis in Dinophysis spp. depends on food uptake aligns well with several recent publications that all argue that these species rely on kleptoplastids, obtained from their ciliate prey, for PA. (Janson & Graneli 2003, Minnhagen & Janson 2006, Wisecaver & Hackett 2010, Kim et al 2012. However, little is known about the prevalence and dynamics of this kleptoplasty.…”

Section: Effects Of Food Availability and Growth Phase On Photosynthementioning

confidence: 99%

Effects of light and food availability on toxin production, growth and photosynthesis in Dinophysis acuminata

Nielsen¹,

Krock²,

Hansen³

2012

Mar. Ecol. Prog. Ser.

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Diarrhetic shellfish poisoning (DSP) toxins constitute a severe health risk to shellfish consumers and a serious economic risk to the shellfish industry. The most prominent producers of DSP toxins are the mixotrophic dinoflagellates Dinophysis spp., which rely on chloroplasts from their prey, the ciliate Mesodinium rubrum; i.e. they are kleptoplastidic. Studies based on field collected material have indicated that cellular toxin contents in Dinophysis spp. vary intraspecifically by several orders of magnitude, but the regulating factors of cellular toxin contents are still poorly understood. We isolated 7 strains of D. acuminata, all of which produced pectenotoxin-2 (PTX-2) in the range of 12.7 to 35.6 pg cell −1 when supplied with abundant nutrients, light and food. One strain was selected for detailed studies on the effects of irradiance and food availability on photoacclimation, photosynthesis, growth and toxin production. Photoacclimation was detected for the first time in this genus, indicating some genetic control of sequestered chloroplasts. Growth and photosynthesis increased 4-fold with irradiances from 7 to 130 µmol photons m −2 s −1 after a minimum of 2 wk under ample food conditions. Despite this, cellular PTX-2 content increased only slightly from (mean ± SE) 4.6 ± 0.3 to 7.8 ± 1.1 pg PTX-2 cell −1 . Toxin production continued for up to 30 d after food was depleted, leading to a build-up of toxin in D. acuminata cells to 24.7 ± 1.7 pg PTX-2 cell −1. Thus, we demonstrate that PTX-2 content is not directly coupled to irradiance and that PTX-2 production is not directly associated with ingestion of ciliate prey. Intraspecific variations in toxicity are instead most likely governed primarily by growth phase and genetic differences between different populations of Dinophysis spp.

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Genetic analyses of Dinophysis spp. support kleptoplastidy

Cited by 49 publications

References 28 publications

Role of food uptake for photosynthesis, growth and survival of the mixotrophic dinoflagellate Dinophysis acuminata

Role of food uptake for photosynthesis, growth and survival of the mixotrophic dinoflagellate Dinophysis acuminata

The Life History and Cell Cycle of Kryptoperidinium foliaceum, A Dinoflagellate with Two Eukaryotic Nuclei

Effects of light and food availability on toxin production, growth and photosynthesis in Dinophysis acuminata

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