Abstract
Cell mortality is a key mechanism that shapes phytoplankton blooms and species dynamics in aquatic environments. Here we show that sterol sulfates (StS) are regulatory molecules of a cell death program in Skeletonema marinoi, a marine diatom-blooming species in temperate coastal waters. The molecules trigger an oxidative burst and production of nitric oxide in a dose-dependent manner. The intracellular level of StS increases with cell ageing and ultimately leads to a mechanism of apoptosis-like death. Disrupting StS biosynthesis by inhibition of the sulfonation step significantly delays the onset of this fatal process and maintains steady growth in algal cells for several days. The autoinhibitory activity of StS demonstrates the functional significance of small metabolites in diatoms. The StS pathway provides another view on cell regulation during bloom dynamics in marine habitats and opens new opportunities for the biochemical control of mass-cultivation of microalgae.
Highlights
Cell mortality is a key mechanism that shapes phytoplankton blooms and species dynamics in aquatic environments
We show that a specific class of secondary metabolites, namely sterol sulfates (StS), can act as cellular signals to induce cell death and growth termination of Skeletonema marinoi, a marine diatom often dominating spring blooms in temperate coastal waters[16]
Magnitude and longevity of the S. marinoi blooms are difficult to model but the species is easy to isolate and maintain in monoclonal cultures that conserve the metabolic characteristics of the original field strains[17,18,19]
Summary
Cell mortality is a key mechanism that shapes phytoplankton blooms and species dynamics in aquatic environments. We show that sterol sulfates (StS) are regulatory molecules of a cell death program in Skeletonema marinoi, a marine diatom-blooming species in temperate coastal waters. Recent evidence suggests that diatoms have sophisticated cell surveillance systems to sense and transduce biotic and abiotic signals at the cellular level[14,15], but the physiological mechanisms controlling the dramatic and abrupt termination of phytoplankton blooms remain very poorly understood[5]. We show that a specific class of secondary metabolites, namely sterol sulfates (StS), can act as cellular signals to induce cell death and growth termination of Skeletonema marinoi, a marine diatom often dominating spring blooms in temperate coastal waters[16]
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