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Evolutionary Maintenance of the PTS2 Protein Import Pathway in the Stramenopile Alga Nannochloropsis

The stramenopile alga Nannochloropsis evolved by secondary endosymbiosis of a red alga by a heterotrophic host cell and emerged as a promising organism for biotechnological applications, such as the production of polyunsaturated fatty acids and biodiesel. Peroxisomes play major roles in fatty acid m...

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Autores principales: Kechasov, Dmitry, de Grahl, Imke, Endries, Pierre, Reumann, Sigrun
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Frontiers Media S.A. 2020
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7710942/
https://www.ncbi.nlm.nih.gov/pubmed/33330478
http://dx.doi.org/10.3389/fcell.2020.593922
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author Kechasov, Dmitry
de Grahl, Imke
Endries, Pierre
Reumann, Sigrun
author_facet Kechasov, Dmitry
de Grahl, Imke
Endries, Pierre
Reumann, Sigrun
author_sort Kechasov, Dmitry
collection PubMed
description The stramenopile alga Nannochloropsis evolved by secondary endosymbiosis of a red alga by a heterotrophic host cell and emerged as a promising organism for biotechnological applications, such as the production of polyunsaturated fatty acids and biodiesel. Peroxisomes play major roles in fatty acid metabolism but experimental analyses of peroxisome biogenesis and metabolism in Nannochloropsis are not reported yet. In fungi, animals, and land plants, soluble proteins of peroxisomes are targeted to the matrix by one of two peroxisome targeting signals (type 1, PTS1, or type 2, PTS2), which are generally conserved across kingdoms and allow the prediction of peroxisomal matrix proteins from nuclear genome sequences. Because diatoms lost the PTS2 pathway secondarily, we investigated its presence in the stramenopile sister group of diatoms, the Eustigmatophyceae, represented by Nannochloropsis. We detected a full-length gene of a putative PEX7 ortholog coding for the cytosolic receptor of PTS2 proteins and demonstrated its expression in Nannochloropsis gaditana. The search for predicted PTS2 cargo proteins in N. gaditana yielded several candidates. In vivo subcellular targeting analyses of representative fusion proteins in different plant expression systems demonstrated that two predicted PTS2 domains were indeed functional and sufficient to direct a reporter protein to peroxisomes. Peroxisome targeting of the predicted PTS2 cargo proteins was further confirmed in Nannochloropsis oceanica by confocal and transmission electron microscopy. Taken together, the results demonstrate for the first time that one group of stramenopile algae maintained the import pathway for PTS2 cargo proteins. To comprehensively map and model the metabolic capabilities of Nannochloropsis peroxisomes, in silico predictions needs to encompass both the PTS1 and the PTS2 matrix proteome.
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spelling pubmed-77109422020-12-15 Evolutionary Maintenance of the PTS2 Protein Import Pathway in the Stramenopile Alga Nannochloropsis Kechasov, Dmitry de Grahl, Imke Endries, Pierre Reumann, Sigrun Front Cell Dev Biol Cell and Developmental Biology The stramenopile alga Nannochloropsis evolved by secondary endosymbiosis of a red alga by a heterotrophic host cell and emerged as a promising organism for biotechnological applications, such as the production of polyunsaturated fatty acids and biodiesel. Peroxisomes play major roles in fatty acid metabolism but experimental analyses of peroxisome biogenesis and metabolism in Nannochloropsis are not reported yet. In fungi, animals, and land plants, soluble proteins of peroxisomes are targeted to the matrix by one of two peroxisome targeting signals (type 1, PTS1, or type 2, PTS2), which are generally conserved across kingdoms and allow the prediction of peroxisomal matrix proteins from nuclear genome sequences. Because diatoms lost the PTS2 pathway secondarily, we investigated its presence in the stramenopile sister group of diatoms, the Eustigmatophyceae, represented by Nannochloropsis. We detected a full-length gene of a putative PEX7 ortholog coding for the cytosolic receptor of PTS2 proteins and demonstrated its expression in Nannochloropsis gaditana. The search for predicted PTS2 cargo proteins in N. gaditana yielded several candidates. In vivo subcellular targeting analyses of representative fusion proteins in different plant expression systems demonstrated that two predicted PTS2 domains were indeed functional and sufficient to direct a reporter protein to peroxisomes. Peroxisome targeting of the predicted PTS2 cargo proteins was further confirmed in Nannochloropsis oceanica by confocal and transmission electron microscopy. Taken together, the results demonstrate for the first time that one group of stramenopile algae maintained the import pathway for PTS2 cargo proteins. To comprehensively map and model the metabolic capabilities of Nannochloropsis peroxisomes, in silico predictions needs to encompass both the PTS1 and the PTS2 matrix proteome. Frontiers Media S.A. 2020-11-19 /pmc/articles/PMC7710942/ /pubmed/33330478 http://dx.doi.org/10.3389/fcell.2020.593922 Text en Copyright © 2020 Kechasov, de Grahl, Endries and Reumann. http://creativecommons.org/licenses/by/4.0/ This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
spellingShingle Cell and Developmental Biology
Kechasov, Dmitry
de Grahl, Imke
Endries, Pierre
Reumann, Sigrun
Evolutionary Maintenance of the PTS2 Protein Import Pathway in the Stramenopile Alga Nannochloropsis
title Evolutionary Maintenance of the PTS2 Protein Import Pathway in the Stramenopile Alga Nannochloropsis
title_full Evolutionary Maintenance of the PTS2 Protein Import Pathway in the Stramenopile Alga Nannochloropsis
title_fullStr Evolutionary Maintenance of the PTS2 Protein Import Pathway in the Stramenopile Alga Nannochloropsis
title_full_unstemmed Evolutionary Maintenance of the PTS2 Protein Import Pathway in the Stramenopile Alga Nannochloropsis
title_short Evolutionary Maintenance of the PTS2 Protein Import Pathway in the Stramenopile Alga Nannochloropsis
title_sort evolutionary maintenance of the pts2 protein import pathway in the stramenopile alga nannochloropsis
topic Cell and Developmental Biology
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7710942/
https://www.ncbi.nlm.nih.gov/pubmed/33330478
http://dx.doi.org/10.3389/fcell.2020.593922
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