Impaired Photoprotection in Phaeodactylum Tricornutum KEA3 Mutants Reveals the Proton Regulatory Circuit of Diatoms Light Acclimation

Overview

Journal New Phytol

Specialty Biology

Date 2022 Jan 29

PMID 35092009

Authors

Claire Seydoux

Mattia Storti

Vasco Giovagnetti

Anna Matuszynska

Erika Guglielmino

Xue Zhao

Cecile Giustini

Yufang Pan

Lander Blommaert

Jhoanell Angulo

Alexander V Ruban

Hanhua Hu

Benjamin Bailleul

Florence Courtois

Guillaume Allorent

Giovanni Finazzi

Affiliations

Soon will be listed here.

Abstract

Diatoms are successful phytoplankton clades able to acclimate to changing environmental conditions, including e.g. variable light intensity. Diatoms are outstanding at dissipating light energy exceeding the maximum photosynthetic electron transfer (PET) capacity via the nonphotochemical quenching (NPQ) process. While the molecular effectors of NPQ as well as the involvement of the proton motive force (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 (minutes) or slow (e.g. diel) changes in light environment, thanks to the presence of a regulatory calcium ion (Ca )-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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