Abundant betaines in reef-building corals and ecological indicators of a photoprotective role

作者：Hill R W^*; Li C; Jones A D; Gunn J P; Frade P R

来源：Coral Reefs, 2010, 29(4): 869-880.

DOI：10.1007/s00338-010-0662-x

• Corals
• Betaines
• Photosystem II
• Photoinhibition
• Dimethylsulfoniopropionate
• DMSP

Betaines are well known as compatible solutes that exert protein- and membrane-stabilizing effects, including protective effects on photosynthesis in plants and free-living algae stressed by high irradiance or unusual temperatures. Betaines, however, have received minimal attention in reef-building corals. One goal of this research was to identify and quantify the betaines of reef-building corals with chemically definitive methods. Metabolite profiling was conducted on 10 species (6 genera) of Cura double dagger ao corals by liquid chromatography/time-of-flight mass spectrometry calibrated using six stable-isotope-labeled internal standards. Glycine betaine (GlyB), proline betaine (ProB), alanine betaine (AlaB), beta-alanine betaine, hydroxyproline betaine (HProB), taurine betaine (TauB), trigonelline (Trig) and the chemically related sulfonium compound dimethylsulfoniopropionate were found in all species. Relative levels of betaines varied across species, with GlyB and ProB being most prominent. Betaines were collectively abundant; estimated total concentrations were 12 to 204 (mean = 75) mmol per liter of tissue. A second goal was to examine ecological patterns in betaine concentrations in field populations of Cura double dagger ao corals. Betaine concentrations exhibited intraspecific patterns that matched a priori predictions for molecules that defend photosynthesis against negative effects of high irradiance. In Madracis mirabilis-which occupies unshaded locations-GlyB, ProB, AlaB, HProB, and Trig were 37-94% more abundant in colonies at 5 m depth (high irradiance) than 20 m. In M. pharensis-which occupies exposed and shaded locations-GlyB, ProB, and AlaB were 30-44% more abundant in unshaded than shaded colonies at one depth. M. senaria exhibited 45-93% increases in concentrations of betaines-GlyB, AlaB, HProB, TauB, and Trig-between early and late in the day, although M. mirabilis and pharensis did not. The results indicate that multiple betaines occur commonly in reef-building coral species, and betaine concentrations are modulated in response to growth light conditions in ways consistent with betaines acting as agents of photoprotection of coral photosynthesis.

• 出版日期2010-12