Posidonia oceanica DMSP(O) data
The database provides contents of dimethylsulfoniopropionate (DMSP) and dimethylsulfoxide (DMSO) in leaf tissues of the seagrass Posidonia oceanica. Current knowledge on the production dynamics of these organosulfur coupounds in coastal and intertidal higher plants is minimal, or even almost non-existent for seagrasses. However, recent work on P. oceanica (and the present study) highlighted this species was the largest producer of DMSP and DMSO reported to date among coastal autotrophs, and most probably the major contributor to the dissolved DMSP and dimethyl sulphide (DMS) pools in coastal waters of the oligotrophic Mediterranean. The aim of this study was to gain a basic, in depth understanding of the natural variability of DMSP and DMSO in P. oceanica leaf tissues. This variability was studied (i) at seasonal and interannual time scales, (ii) with depth, (iii) in relation to the ageing of leaf tissues and (iv), in the context of ocean warming, with water temperature. Results showed that DMSP and DMSO production and content dynamics in P. oceanica were related to the plant biology/physiology, in particular to its growth cycle and productivity (varying over time and with depth). The modelled relationships with temperature would result from an indirect effect on molecules via seagrass growth. A notable characteristic was the constant ratio of the two molecule contents, indicative of a strong biochemical link between DMSP and DMSO in that species. Among the potential physiological roles played by these molecules, protection against oxidative stress, including thermal stress, seems likely.
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Posidonia oceanica samples were collected weekly to seasonally by scuba diving during a period of 3.5 years (April 2015 - August 2018) in the pristine Revellata Bay (Calvi, northwestern Corsica, France; 42.580°N, 8.725°E). Random sampling was performed in triplicate on orthotropic shoots (i.e. vertical growth), by cutting the leaves just above the meristem area. Quickly after the end of the dive, seagrass leaf samples were dissected (leaf class-rank, leaf section), cleaned of epiphytes, and stored frozen until analysis. In the laboratory, DMSP and DMSO contents in P. oceanica leaf samples (7-50 mg of 3 mm2 square fresh leaf tissue fragments) were measured after conversion into DMS using the headspace technique with a gas chromatograph (GC) with a flame photometric detector (FPD). First, DMSP was cleaved into DMS and acrylate in a NaOH solution; next, DMSO was reduced in DMS with TiCl3 in an acid solution. The GC-FPD peaks of DMS were converted into DMSP and DMSO concentrations from a series of standards of known concentrations. DMSP, DMSO and DMSP:DMSO ratio data were analysed in R with RStudio, using graphs and models (median regression, best linear fit, linear mixed effect model, analysis of variance).