Screen of Diatom Dissolved Lipidomes Reveals Oxylipins Associated with Silicon Limitation and Growth Phase

Marine diatoms are an important group of phytoplankton that can shape marine ecosystems and global carbon cycling. When stressed, either physiologically or by grazing, diatoms release oxidized, lipid-derived signals known as oxylipins. Diatom-derived oxylipins are proposed to serve as defense and signaling chemicals that affect multiple components of marine ecosystems. Despite their role as chemical mediators, much less is known about types of stressors that induce oxylipin release and the diversity of those compounds. Therefore, to elucidate the kinds of diatom-derived oxylipins produced during stress, we profiled the spectrum of dissolved lipids of five diatom species in culture under silicon limitation and across growth phase using ultra-high performance liquid chromatography coupled to a high-resolution accurate mass spectrometer. In this study, we present evidence that physiological changes associated with Si-limitation elicit the extracellular release of LOFAs across five diatom species. For diatoms like Skeletonema japonicum and Pseudo-nitzschia multiseries, silicon limitation also induced a distinct lipidomic signature driven by various oxylipins known to be allelopathic. While their lipoxygenases were found to be different, S. japonicum and P. multiseries had the most similar dissolved lipidomes which suggests alternative controls on oxylipin biosynthesis. Consequently, the increased release of oxylipins with silicon limitation poses implications for diatoms at sea which can elevate local oxylipin concentrations during blooms, potentially affecting ecosystems and biogeochemistry.