DMSP biosynthesis by an animal and its role in coral thermal stress response

Until now, dimethylsulphoniopropionate (DMSP), an important component in the sulphur cycle, has been thought to be produced solely by algae and some plants; however, this study shows that the coral animal also produces DMSP, in addition to that produced by the coral’s algal symbiont, with potential implications for the sulphur cycle and its climatic consequences as corals and their symbionts are affected by global change. DMSP biosynthesis in coral animals Dimethylsulphoniopropionate (DMSP) is a widely distributed metabolite that is converted by marine bacteria to the volatile gas dimethylsulphide (DMS), a major contributor of sulphur to the atmosphere that contributes to cloud formation and hence influences climate. Here Jean-Baptiste Raina et al . report DMSP formation by two common reef-building coral species, Acropora millepora and Acropora tenuis . This comes as a surprise — previously it was thought that DMSP was produced solely by algae (including species symbiotic in coral) and some plants. DMSP biosynthesis may help the coral animals to survive conditions of thermal stress. This finding could have implications for how DMSP production responds to the effects of global change on corals and their symbionts. Globally, reef-building corals are the most prolific producers of dimethylsulphoniopropionate (DMSP) 1 , 2 , a central molecule in the marine sulphur cycle and precursor of the climate-active gas dimethylsulphide 3 , 4 . At present, DMSP production by corals is attributed entirely to their algal endosymbiont, Symbiodinium 2 . Combining chemical, genomic and molecular approaches, we show that coral juveniles produce DMSP in the absence of algal symbionts. DMSP levels increased up to 54% over time in newly settled coral juveniles lacking algal endosymbionts, and further increases, up to 76%, were recorded when juveniles were subjected to thermal stress. We uncovered coral orthologues of two algal genes recently identified in DMSP biosynthesis, strongly indicating that corals possess the enzymatic machinery necessary for DMSP production. Our results overturn the paradigm that photosynthetic organisms are the sole biological source of DMSP, and highlight the double jeopardy represented by worldwide declining coral cover, as the potential to alleviate thermal stress through coral-produced DMSP declines correspondingly.