Osmoacclimation in Enteromorpha intestinalis: long-term effects of osmotic stress on organic solute accumulation

Edwards, D. M.; Reed, Robert H.; Stewart, W. D. P.

doi:10.1007/bf00391537

Cited by 58 publications

(54 citation statements)

References 30 publications

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“…As summarized in Table VII, all three enzymes show high affinities for their substrates and have extractable activities 4-to 25-fold above our highest estimate of the in vivo rate of DMSP synthesis (4.2 nmol h Ϫ1 g Ϫ1 fresh weight). Moreover, much of the activity was probably not extracted because our extracts contained about 0.5 mg protein g Ϫ1 fresh weight, whereas the total protein content (Kjeldahl n ϫ 6.25) of E. intestinalis fronds was found to be 5.9 mg g Ϫ1 fresh weight, in accord with published values (2-10 mg g Ϫ1 fresh weight; Edwards et al, 1988).…”

Section: Discussionsupporting

confidence: 89%

Identification and Stereospecificity of the First Three Enzymes of 3-Dimethylsulfoniopropionate Biosynthesis in a Chlorophyte Alga1

et al. 1998

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Many marine algae produce 3-dimethylsulfoniopropionate (DMSP), a potent osmoprotective compound whose degradation product dimethylsulfide plays a central role in the biogeochemical S cycle. Algae are known to synthesize DMSP via the four-step pathway, L-Met 3 4-methylthio-2-oxobutyrate 3 4-methylthio-2-hydroxybutyrate 3 4-dimethylsulfonio-2-hydroxy-butyrate (DM-SHB) 3 DMSP. Substrate-specific enzymes catalyzing the first three steps in this pathway were detected and partially characterized in cell-free extracts of the chlorophyte alga Enteromorpha intestinalis. The first is a 2-oxoglutarate-dependent aminotransferase, the second an NADPH-linked reductase, and the third an S-adenosylmethioninedependent methyltransferase. Sensitive radiometric assays were developed for these enzymes, and used to show that their activities are high enough to account for the estimated in vivo flux from Met to DMSP. The activities of these enzymes in other DMSP-rich chlorophyte algae were at least as high as those in E. intestinalis, but were >20-fold lower in algae without DMSP. The reductase and methyltransferase were specific for the D-enantiomer of 4-methylthio-2-hydroxybutyrate in vitro, and both the methyltransferase step and the step(s) converting DMSHB to DMSP were shown to prefer D-enantiomers in vivo. The intermediate DMSHB was shown to act as an osmoprotectant, which indicates that the first three steps of the DMSP synthesis pathway may be sufficient to confer osmotolerance.

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Section: Discussionsupporting

confidence: 89%

Identification and Stereospecificity of the First Three Enzymes of 3-Dimethylsulfoniopropionate Biosynthesis in a Chlorophyte Alga1

et al. 1998

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“…Among the different physiological and ecological roles that DMSP could play in P. oceanica some can be excluded. The role as a cryoprotectant can be excluded as P. oceanica is present in areas with minimal temperatures >9 • C. DMSP is a compatible solute and changes in DMSP intracellular concentration have been hypothesized to allow algae to cope with short-term osmotic changes (osmoregulation) as by the intertidal algae Enteromorpha intestinalis (Edwards et al, 1988) and the intertidal epiphyte Polysiphonia lanosa (Reed, 1983). The strong increase in DMSP leaf content during summer is inconsistent with the relatively small increase of salinity from winter to summer of <0.5 (data not shown), as well as with the strong decrease in summer of DMSP leaf content with depth while salinity usually only decreases by 0.02 from 10 m to 30 m (data not shown).…”

Section: Discussionmentioning

confidence: 99%

Seasonal and spatial variability of dimethylsulfoniopropionate (DMSP) in the Mediterranean seagrass Posidonia oceanica

Borges

Champenois

2015

Aquatic Botany

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a b s t r a c tWe investigated for the first time the occurrence of dimethylsulfoniopropionate (DMSP) in the leaves of Posidonia oceanica and we report its variability during 4 sampling periods covering the seasonal cycle (February, June, August and November) and along a gradient from 10 m to 30 m depth. The P. oceanica leaf DMSP content expressed per mass of dry weight (dw) ranged from 0.1 to 33.9 mol g dw −1 and averaged 5.0 mol g dw −1 . It was higher than the DMSP content of roots and rhizomes that averaged ∼0.5 mol g dw −1 . The leaf DMSP content showed seasonal variations, being highest in summer when primary production and biomass of P. oceanica were also highest. In August, the leaf DMSP content showed variations with depth, increasing from 30 m to 10 m depth. In summer, the leaf DMSP content was highest in the youngest sections of leaves (closest to base) than in the older ones (closest to apex). The seasonal and depth distribution suggest that the DMSP leaf content is positively related to irradiance, hence, we hypothesize that DMSP in P. oceanica plays a role as an antioxidant against reactive oxygen species, although we cannot unambiguously exclude other potential roles such as grazer deterrent. The average leaf DMSP content of P. oceanica is modest compared to high DMSP producing macroalgae and phytoplankton. Yet, the integrated DMSP stock associated to the meadows of P. oceanica is very large due to its enormous biomass, and at the community level it is 2 orders of magnitude higher than the potential integrated DMSP stock related to phytoplankton in the same area.

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“…The synthesis or degradation of organic osmolytes, in contrast, occurs at the timescale of several hours to days, depending on the compound and the algal species (e.g. Edwards et al, 1988;Kirst, 1989). Dickson et al (1980) showed that the intracellular concentrations of small ions in Ulva lactuca changed quickly with oscillations in salinity (mimicking the tidal rhythm), while the concentrations of organic osmolytes (here sugars and DMSP) remained almost unaffected by changes in salinity at this timescale.…”

Section: Discussionmentioning

confidence: 99%

The effect of temporal variability in salinity on the invasive red alga Gracilaria vermiculophylla

Nejrup

Pedersen

2012

European Journal of Phycology

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Non-native, invasive species are often characterized by being tolerant to environmental stressors, leaving them more fit relative to native species. The red alga Gracilaria vermiculophylla originates from the NW Pacific but has recently spread along the coastlines of Western Europe, where it has become abundant in many shallow, soft-bottom estuaries. Salinity is important for the local and regional distribution of algae. The distribution of G. vermiculophylla in Europe suggests that it thrives well in hyposaline environments and that it may be more fit than some native algae under such conditions. Little, however, is known about the ecophysiology of G. vermiculophylla and it is therefore difficult to predict its spread and future distribution. Laboratory experiments with G. vermiculophylla showed that steady-state salinity above 15 psu was optimal for growth and that the growth rate was reduced at salinities below 15 psu. Variable salinity reduced the growth rate and larger oscillations were more stressful than small ones. Exposure to very low salinity (0-5 psu) was stressful for the alga and algae exposed to these low levels for 2-4 days were unable to recover fully. Gracilaria vermiculophylla did not seem to perform better in hyposaline conditions than many native, estuarine species. The present distribution of G. vermiculophylla in Scandinavia can be explained well by its response to salinity, but this may not explain its present success relative to many naturally occurring algal species.

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Osmoacclimation in Enteromorpha intestinalis: long-term effects of osmotic stress on organic solute accumulation

Cited by 58 publications

References 30 publications

Identification and Stereospecificity of the First Three Enzymes of 3-Dimethylsulfoniopropionate Biosynthesis in a Chlorophyte Alga1

Identification and Stereospecificity of the First Three Enzymes of 3-Dimethylsulfoniopropionate Biosynthesis in a Chlorophyte Alga1

Seasonal and spatial variability of dimethylsulfoniopropionate (DMSP) in the Mediterranean seagrass Posidonia oceanica

The effect of temporal variability in salinity on the invasive red alga Gracilaria vermiculophylla

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