The fine-tuning of NPQ in diatoms relies on the regulation of both xanthophyll cycle enzymes

Abstract Diatoms possess an efficient mechanism to dissipate photons as heat in conditions of excess light, which is visualized as the Non-Photochemical Quenching of chlorophyll a fluorescence (NPQ). In most diatom species, NPQ is proportional to the concentration of the xanthophyll cycle pigment di...

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Autores principales:	Lander Blommaert, Lamia Chafai, Benjamin Bailleul
Formato:	article
Lenguaje:	EN
Publicado:	Nature Portfolio 2021
Materias:	Medicine R Science Q
Acceso en línea:	https://doaj.org/article/1472e972068643ecaec51dbc415821e9
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spelling	oai:doaj.org-article:1472e972068643ecaec51dbc415821e92021-12-02T17:41:07ZThe fine-tuning of NPQ in diatoms relies on the regulation of both xanthophyll cycle enzymes10.1038/s41598-021-91483-x2045-2322https://doaj.org/article/1472e972068643ecaec51dbc415821e92021-06-01T00:00:00Zhttps://doi.org/10.1038/s41598-021-91483-xhttps://doaj.org/toc/2045-2322Abstract Diatoms possess an efficient mechanism to dissipate photons as heat in conditions of excess light, which is visualized as the Non-Photochemical Quenching of chlorophyll a fluorescence (NPQ). In most diatom species, NPQ is proportional to the concentration of the xanthophyll cycle pigment diatoxanthin formed from diadinoxanthin by the diadinoxanthin de-epoxidase enzyme. The reverse reaction is performed by the diatoxanthin epoxidase. Despite the xanthophyll cycle’s central role in photoprotection, its regulation is not yet well understood. The proportionality between diatoxanthin and NPQ allowed us to calculate the activity of both xanthophyll cycle enzymes in the model diatom Phaeodactylum tricornutum from NPQ kinetics. From there, we explored the light-dependency of the activity of both enzymes. Our results demonstrate that a tight regulation of both enzymes is key to fine-tune NPQ: (i) the rate constant of diadinoxanthin de-epoxidation is low under a light-limiting regime but increases as photosynthesis saturates, probably due to the thylakoidal proton gradient ΔpH (ii) the rate constant of diatoxanthin epoxidation exhibits an optimum under low light and decreases in the dark due to an insufficiency of the co-factor NADPH as well as in higher light through an as yet unresolved inhibition mechanism, that is unlikely to be related to the ΔpH. We observed that the suppression of NPQ by an uncoupler was due to an accelerated diatoxanthin epoxidation enzyme rather than to the usually hypothesized inhibition of the diadinoxanthin de-epoxidation enzyme.Lander BlommaertLamia ChafaiBenjamin BailleulNature PortfolioarticleMedicineRScienceQENScientific Reports, Vol 11, Iss 1, Pp 1-16 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	Medicine R Science Q
spellingShingle	Medicine R Science Q Lander Blommaert Lamia Chafai Benjamin Bailleul The fine-tuning of NPQ in diatoms relies on the regulation of both xanthophyll cycle enzymes
description	Abstract Diatoms possess an efficient mechanism to dissipate photons as heat in conditions of excess light, which is visualized as the Non-Photochemical Quenching of chlorophyll a fluorescence (NPQ). In most diatom species, NPQ is proportional to the concentration of the xanthophyll cycle pigment diatoxanthin formed from diadinoxanthin by the diadinoxanthin de-epoxidase enzyme. The reverse reaction is performed by the diatoxanthin epoxidase. Despite the xanthophyll cycle’s central role in photoprotection, its regulation is not yet well understood. The proportionality between diatoxanthin and NPQ allowed us to calculate the activity of both xanthophyll cycle enzymes in the model diatom Phaeodactylum tricornutum from NPQ kinetics. From there, we explored the light-dependency of the activity of both enzymes. Our results demonstrate that a tight regulation of both enzymes is key to fine-tune NPQ: (i) the rate constant of diadinoxanthin de-epoxidation is low under a light-limiting regime but increases as photosynthesis saturates, probably due to the thylakoidal proton gradient ΔpH (ii) the rate constant of diatoxanthin epoxidation exhibits an optimum under low light and decreases in the dark due to an insufficiency of the co-factor NADPH as well as in higher light through an as yet unresolved inhibition mechanism, that is unlikely to be related to the ΔpH. We observed that the suppression of NPQ by an uncoupler was due to an accelerated diatoxanthin epoxidation enzyme rather than to the usually hypothesized inhibition of the diadinoxanthin de-epoxidation enzyme.
format	article
author	Lander Blommaert Lamia Chafai Benjamin Bailleul
author_facet	Lander Blommaert Lamia Chafai Benjamin Bailleul
author_sort	Lander Blommaert
title	The fine-tuning of NPQ in diatoms relies on the regulation of both xanthophyll cycle enzymes
title_short	The fine-tuning of NPQ in diatoms relies on the regulation of both xanthophyll cycle enzymes
title_full	The fine-tuning of NPQ in diatoms relies on the regulation of both xanthophyll cycle enzymes
title_fullStr	The fine-tuning of NPQ in diatoms relies on the regulation of both xanthophyll cycle enzymes
title_full_unstemmed	The fine-tuning of NPQ in diatoms relies on the regulation of both xanthophyll cycle enzymes
title_sort	fine-tuning of npq in diatoms relies on the regulation of both xanthophyll cycle enzymes
publisher	Nature Portfolio
publishDate	2021
url	https://doaj.org/article/1472e972068643ecaec51dbc415821e9
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The fine-tuning of NPQ in diatoms relies on the regulation of both xanthophyll cycle enzymes

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