Affiliation:
1. School of Biological and Chemical Sciences, Queen Mary University of London, London E1 4NS, UK
2. Laboratoire de Biologie du Chloroplaste et Perception de la Lumière Chez les Micro-algues, UMR7141, CNRS, Sorbonne Université, Institut de Biologie Physico-Chimique, Paris 75005, France
Abstract
Abstract
Light harvesting is regulated by a process triggered by the acidification of the thylakoid lumen, known as nonphotochemical “energy-dependent quenching” (qE). In diatoms, qE is controlled by the light-harvesting complex (LHC) protein LHCX1, while the LHC stress-related (LHCSR) and photosystem II subunit S proteins are essential for green algae and plants, respectively. Here, we report a biochemical and molecular characterization of LHCX1 to investigate its role in qE. We found that, when grown under intermittent light, Phaeodactylum tricornutum forms very large qE, due to LHCX1 constitutive upregulation. This “super qE” is abolished in LHCX1 knockout mutants. Biochemical and spectroscopic analyses of LHCX1 reveal that this protein might differ in the character of binding pigments relative to the major pool of light-harvesting antenna proteins. The possibility of transient pigment binding or not binding pigments at all is discussed. Targeted mutagenesis of putative protonatable residues (D95 and E205) in transgenic P. tricornutum lines does not alter qE capacity, showing that they are not involved in sensing lumen pH, differently from residues conserved in LHCSR3. Our results suggest functional divergence between LHCX1 and LHCSR3 in qE modulation. We propose that LHCX1 evolved independently to facilitate dynamic tracking of light fluctuations in turbulent waters. The evolution of LHCX(-like) proteins in organisms with secondary red plastids, such as diatoms, might have conferred a selective advantage in the control of dynamic photoprotection, ultimately resulting in their ecological success.
Funder
The Leverhulme Trust
Biotechnology and Biological Sciences Research Council
The Royal Society Wolfson Research Merit Award
European Assemble plus
Association of European Marine Biological Research Laboratories Expanded
Fondation Bettencourt-Schueller
Gordon and Betty Moore Foundation
Publisher
Oxford University Press (OUP)
Subject
Plant Science,Genetics,Physiology
Cited by
8 articles.
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