Physiological stress and cell death in marine phytoplankton: Induction of proteases in response to nitrogen or light limitation

John A. Berges, Paul Falkowski

Research output: Contribution to journalArticle

220 Scopus citations

Abstract

The physiological processes of natural phytoplankton mortality due to environmental stress (vs. that caused by sedimentation and predation) are poorly understood. Cell survival was examined in batch cultures of the diatom Thalassiosira weissflogii and the chlorophyte Dunaliella tertiolecta during deprivation of fixed nitrogen or light. Despite severe impairment of photosynthetic efficiencies, both species remained viable during 2 weeks of N starvation. Under N stress, a specific protease was induced in the diatom, overall activity of proteases doubled, and there was gradual, selective loss of certain proteins, especially ribulose 1,5-bisphosphate carboxylase/oxygenase. Light-deprived diatoms were virtually unaffected, but the chlorophyte underwent catastrophic cell death after about 6 d of darkness. Cell death coincided with a large increase in protease activity and the induction of a specific protease. Although we cannot completely rule out roles for viruses or bacteria in the losses of cells, the consistent timing, the unique response to stress, and the coincident expression of a specific protease strongly suggest that the process is a form of autocatalyzed cell death, such as apoptosis. While of uncertain adaptive significance, phytoplankton cell death may have implications for species succession and cycling of organic matter in aquatic ecosystems.

Original languageEnglish (US)
Pages (from-to)129-135
Number of pages7
JournalLimnology and Oceanography
Volume43
Issue number1
DOIs
StatePublished - Jan 1998

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All Science Journal Classification (ASJC) codes

  • Oceanography
  • Aquatic Science

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