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Identification of sequence motifs in Lhcx proteins that confer qE-based photoprotection in the diatom Phaeodactylum tricornutum

Identification of sequence motifs in Lhcx proteins that confer qE-based photoprotection in the diatom Phaeodactylum tricornutum

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BUCK, Jochen M., Peter G. KROTH, Bernard LEPETIT, 2021. Identification of sequence motifs in Lhcx proteins that confer qE-based photoprotection in the diatom Phaeodactylum tricornutum. In: The Plant Journal. Wiley. 108(6), pp. 1721-1734. ISSN 0960-7412. eISSN 1365-313X. Available under: doi: 10.1111/tpj.15539

@article{Buck2021-12Ident-55293, title={Identification of sequence motifs in Lhcx proteins that confer qE-based photoprotection in the diatom Phaeodactylum tricornutum}, year={2021}, doi={10.1111/tpj.15539}, number={6}, volume={108}, issn={0960-7412}, journal={The Plant Journal}, pages={1721--1734}, author={Buck, Jochen M. and Kroth, Peter G. and Lepetit, Bernard} }

Photosynthetic organisms in nature often experience light fluctuations. While low light conditions limit the energy uptake by algae, light absorption exceeding the maximal rate of photosynthesis may go along with enhanced formation of potentially toxic reactive oxygen species. To preempt high light induced photodamage, photosynthetic organisms evolved numerous photoprotective mechanisms. Amongst these, energy-dependent fluorescence quenching (qE) provides a rapid mechanism to thermally dissipate excessively absorbed energy.<br /><br />Diatoms thrive in all aquatic environments and thus belong to the most important primary producers on earth. qE in diatoms is provided by a concerted action of Lhcx proteins and the xanthophyll cycle pigment diatoxanthin. While the exact Lhcx activation mechanism of diatom qE is unknown, two lumen-exposed acidic amino acids within Lhcx proteins were proposed to function as regulatory switches upon light induced lumenal acidification. By introducing a modified Lhcx1 lacking these amino acids into a Phaeodactylum tricornutum Lhcx1-null qE knockout line, we demonstrate that qE is unaffected by these two amino acids. Based on sequence comparisons with Lhcx4, being incapable of providing qE, we perform domain swap experiments of Lhcx4 with Lhcx1 and identify two peptide motifs involved in conferring qE. Within one of these motifs, we identify a tryptophan residue with a major influence on qE establishment. This tryptophan residue is located in close proximity to the diadinoxanthin/diatoxanthin binding site based on the recently revealed diatom Lhc crystal structure. Our findings provide a structural explanation for the intimate link of Lhcx and diatoxanthin in providing qE in diatoms. eng 2021-12 Identification of sequence motifs in Lhcx proteins that confer qE-based photoprotection in the diatom Phaeodactylum tricornutum terms-of-use 2021-10-19T14:00:01Z 2021-10-19T14:00:01Z Kroth, Peter G. Kroth, Peter G. Lepetit, Bernard Buck, Jochen M. Buck, Jochen M. Lepetit, Bernard

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