ULTRAVIOLET SUNSCREENS IN <i>GYMNODINIUM SANGUINEUM</i> (DINOPHYCEAE): MYCOSPORINE‐LIKE AMINO ACIDS PROTECT AGAINST INHIBITION OF PHOTOSYNTHESIS

Neale, Patrick J.; Banaszak, Anastazia T.; Jarriel, Catherine R.

doi:10.1046/j.1529-8817.1998.340928.x

Cited by 207 publications

(193 citation statements)

References 48 publications

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“…The dominance of 2 MAAs absorbing at roughly the same wavelength in Ht gave a narrower absorbance peak. Such large UV absorbance peaks for filtered cells have been reported in some other studies (Neale et al 1998, Sosik 1999) and is related to the effect of handling (at least for these dinoflagellates; Laurion et al 2003). These results suggest that a gradual release of MAAs started immediately after or during filtration, while freezing greatly increased this release.…”

Section: Resultssupporting

confidence: 78%

“…These concentrations fall in the range of values found in cultured and natural marine dinoflagellates (e.g. Neale et al 1998, Whitehead & Vernet 2000see Laurion et al 2002 for a comparison table). Carreto et al (2001) found a lower MA concentration in cultures of A. tamarense (6.18 pg cell -1 ), likely related to the low growth irradiance used (65 µmol photons m -2 s -1 ).…”

Section: Resultsmentioning

confidence: 55%

“…Sathyendranath et al 1987). A nonhomogenous distribution of MAAs in the cells, targeted around UV-sensitive organelles for increased protection efficiency, has been suggested by Neale et al (1998) and could be a major cause of this UV flattening. Even if measured cell absorption of UV radiation is reduced when MAAs are packaged, the protection efficiency of specific targets would increase, affecting the estimation of sunscreen photoprotection, i.e.…”

Section: Discussionmentioning

confidence: 99%

“…Cells possess protective mechanisms against UV radiation (Roy 2000), which influence their specific absorption in this waveband. For instance, the accumulation of mycosporine-like amino acids (MAAs) can affect the sensitivity of microalgae to UV radiation (Garcia-Pichel & Castenholz 1993, Neale et al 1998. Hence, measurement of cell absorption in the UV range is a factor of interest in photobiology, a field of increasing importance in view of the decline in the stratospheric ozone levels and the climate-induced changes in water UV transparency (Williamson et al 1996).…”

Section: Introductionmentioning

confidence: 99%

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Packaging of mycosporine-like amino acids in dinoflagellates

Laurion¹,

Blouin²,

Roy³

2004

Mar. Ecol. Prog. Ser.

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Synthesis of mycosporine-like amino acids (MAAs) can significantly protect phytoplankton cells against damaging ultraviolet (UV) radiation, depending on the concentration, type and cellular distribution of these UV sunscreens. We addressed the hypothesis that MAAs are concentrated around UV-sensitive organelles for improved efficiency, thereby increasing their 'package effect'. This was investigated for 2 species of MAA-producing dinoflagellates, with comparative analyses of a MAA-free diatom. Spectral absorbance of dinoflagellates suspended in their growth medium was relatively small throughout the MAA-absorbing region despite high concentrations of these compounds (determined by HPLC), suggesting that MAAs are highly packaged in intact cells. The measured in vivo absorbance of suspended and filtered phytoplankton cells revealed an extracellular release of water-soluble MAAs during freezing. The release of MAAs upon thawing enabled the calculation of an MAA packaging index based on the comparison between absorption characteristics before (MAAs inside cells in suspension) and after freezing (MAAs released from cells on thawed filters). Additionally, MAA packaging was evaluated from the reconstruction of absorption spectra from the individual MAA concentration. Consistent with our hypothesis, the results showed that UV absorption was up to 80% lower in the intact cells relative to the MAAs dissolved in solution. These results imply a high degree of MAA packaging in these dinoflagellates, that may increase the protection efficiency for specific cellular targets. KEY WORDS: Package effect · Photoprotection · MAAs · UV-absorbing compounds · Bio-optics · Alexandrium tamarense Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 279: [297][298][299][300][301][302][303] 2004 Pigment packaging has a major influence on the light harvesting efficiency of algal cells (Kirk 1994 and references therein). The absorption efficiency of phytoplankton is a non-linear function of pigment concentration, thylakoid arrangement and cell size (Berner et al. 1989, Nelson et al. 1993. A similar packaging effect for UV sunscreens could be of importance to MAAproducing phytoplankton. For UV sunscreens however, packaging can be viewed as effectiveness, since with equal investments, a large organism would benefit more than a small one. The bio-optical model developed by Garcia-Pichel (1994) indicates that MAAs should only be marginally effective at reducing UV radiation due to the short pathlength characteristic of relatively small phytoplankton cells (assuming a homogeneous cytoplasmic distribution of MAAs). However, the localization of MAAs around UV-sensitive organelles (packaged MAAs) might increase their efficiency, although this has not yet been assessed. MAA packaging has been suggested previously for the colonial prymnesiophyte Phaeocystis antarctica (Davidson & Marchant 1994, Moisan & Mitchell 2001. However, MAA concentrations observed in colonial prymnesiophytes appeared too h...

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Section: Resultssupporting

confidence: 78%

Section: Resultsmentioning

confidence: 55%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Packaging of mycosporine-like amino acids in dinoflagellates

Laurion¹,

Blouin²,

Roy³

2004

Mar. Ecol. Prog. Ser.

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“…These mechanisms may affect many possible targets such as nucleic acids, PSII, ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) or membrane lipids, among others (for review Vincent and Neale 2000). Damage to these cellular components results in inhibition of photosynthetic carbon assimilation (Day and Neale 2002) with specific effects dependent on wavelength (Cullen and Neale 1997, Neale et al 1998, Sobrino et al 2005.…”

Section: Introductionmentioning

confidence: 99%

Biological weighting function for xanthophyll de‐epoxidation induced by ultraviolet radiation

Sobrino

Neale

Montero

et al. 2005

Physiologia Plantarum

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The light‐induced de‐epoxidation of xanthophylls is an important photoprotective mechanism in plants and algae. Exposure to ultraviolet radiation (UVR, 280–400 nm) can change the extent of xanthophyll de‐epoxidation, but different types of responses have been reported. The de‐epoxidation of violaxanthin (V) to zeaxanthin (Z), via the intermediate antheraxanthin, during exposure to UVR and photosynthetically active radiation (PAR, 400–700 nm) was studied in the marine picoplankter Nannochloropsis gaditana (Eustigmatophyceae) Lubián. Exposures used a filtered xenon lamp, which gives PAR and UVR similar to natural proportions. Exposure to UVR plus PAR increased de‐epoxidation compared with under PAR alone. In addition, de‐epoxidation increased with the irradiance and with the inclusion of shorter wavelengths in the spectrum. The spectral dependence of light‐induced de‐epoxidation under UVR and PAR exposure was well described by a model of epoxidation state (EPS) employing a biological weighting function (BWF). This model fit measured EPS in eight spectral treatments using Schott long pass filters, with six intensities for each filter, with a R2 = 0.90. The model predicts that 56% of violaxanthin is de‐epoxidated, of which UVR can induce as much as 24%. The BWF for EPS was similar in shape to the BWF for UVR inhibition of photosynthetic carbon assimilation in N. gaditana but with about 22‐fold lower effectiveness. These results demonstrate a connection between the presence of de‐epoxidated Z and the inhibition under UVR exposures in N. gaditana. Nevertheless, they also indicate that de‐epoxidation is insufficient to prevent UVR inhibition in this species.

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