Uptake of dimethylsulphoniopropionate (DMSP) reduces free reactive oxygen species (ROS) during late exponential growth in the diatom Thalassiosira weissflogii grown under three salinities

Abstract

Dimethylsulphoniopropionate (DMSP) is one of the most abundant and widespread organic sulfur molecules in the marine environment and has substantial physiological and ecological importance, from subcellular to global scales. Despite its diverse range of implications in the environment, little understanding of the physiological role of DMSP in the cell exists. Here, we report the physiological response of a non-DMSP-producing diatom Thalassiosira weissflogii grown at different salinities (15, 35 and 55 ppt) in the presence and absence of DMSP. Hypersaline conditions (55 ppt) negatively affected growth rate and hyposaline conditions (15 ppt) caused an increase in cell volume, yet no effect was observed on the photophysiological state of the algae, demonstrating a broad salinity tolerance in T. weissflogii. Addition of DMSP and subsequent uptake by T. weissflogii had no effect on the salinity-induced symptoms. Importantly, using a non-DMSP-producing diatom, we observed some of the first direct evidence of the intracellular role of DMSP as an antioxidant through the quenching of damaging reactive oxygen species (ROS), which based on its pattern, was likely due to the growth phase of the culture. This study confirms the utility of T. weissflogii as a model organism for DMSP-related physiological studies, with results revealing that DMSP accumulation reduces growth-related reactive oxygen in T. weissflogii.