Last publication: In Simple Words


Does phytoplankton protect itself from stress during photosynthesis in the same way as plants?

Cover New Phytologist, Volume 234, Issue 2 Copyright: © New Phytologist


  • Diatoms are successful phytoplankton clades able to acclimate to changing environmental conditions, including for example variable light intensity. Diatoms are outstanding at dissipating light energy exceeding the maximum photosynthetic electron transfer, called PET, capacity via the nonphotochemical quenching, called NPQ, process. While the molecular effectors of NPQ as well as the involvement of the proton motive force, called PMF, in its regulation are known, the regulators of the PET/PMF relationship remain unidentified in diatoms.
  • We generated mutants of the H+/K+ antiporter KEA3 in the model diatom Phaeodactylum tricornutum.
  • Loss of KEA3 activity affects the PET/PMF coupling and NPQ responses at the onset of illumination, during transients and in steady-state conditions. Thus, this antiporter is a main regulator of the PET/PMF coupling. Consistent with this conclusion, a parsimonious model including only two free components, KEA3 and the diadinoxanthin de-epoxidase, describes most of the feedback loops between PET and NPQ.
  • This simple regulatory system allows for efficient responses to fast or slow, for example diel, changes in light environment, thanks to the presence of a regulatory calcium ion-binding domain in KEA3 modulating its activity. This circuit is likely tuned by the NPQ-effector proteins, LHCXs, providing diatoms with the required flexibility to thrive in different ocean provinces.

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