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  • Oxford University Press (OUP)  (2)
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  • Oxford University Press (OUP)  (2)
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  • 1
    In: The Plant Cell, Oxford University Press (OUP), Vol. 35, No. 8 ( 2023-08-02), p. 3053-3072
    Kurzfassung: The ketocarotenoid fucoxanthin and its derivatives can absorb blue–green light enriched in marine environments. Fucoxanthin is widely adopted by phytoplankton species as a main light-harvesting pigment, in contrast to land plants that primarily employ chlorophylls. Despite its supreme abundance in the oceans, the last steps of fucoxanthin biosynthesis have remained elusive. Here, we identified the carotenoid isomerase-like protein CRTISO5 as the diatom fucoxanthin synthase that is related to the carotenoid cis–trans isomerase CRTISO from land plants but harbors unexpected enzymatic activity. A crtiso5 knockout mutant in the model diatom Phaeodactylum tricornutum completely lacked fucoxanthin and accumulated the acetylenic carotenoid phaneroxanthin. Recombinant CRTISO5 converted phaneroxanthin into fucoxanthin in vitro by hydrating its carbon–carbon triple bond, instead of functioning as an isomerase. Molecular docking and mutational analyses revealed residues essential for this activity. Furthermore, a photophysiological characterization of the crtiso5 mutant revealed a major structural and functional role of fucoxanthin in photosynthetic pigment–protein complexes of diatoms. As CRTISO5 hydrates an internal alkyne physiologically, the enzyme has unique potential for biocatalytic applications. The discovery of CRTISO5 illustrates how neofunctionalization leads to major diversification events in evolution of photosynthetic mechanisms and the prominent brown coloration of most marine photosynthetic eukaryotes.
    Materialart: Online-Ressource
    ISSN: 1040-4651 , 1532-298X
    Sprache: Englisch
    Verlag: Oxford University Press (OUP)
    Publikationsdatum: 2023
    ZDB Id: 623171-8
    ZDB Id: 2004373-9
    SSG: 12
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 2
    In: Plant And Cell Physiology, Oxford University Press (OUP), Vol. 64, No. 6 ( 2023-06-15), p. 622-636
    Kurzfassung: In addition to being important primary productive forces in marine ecosystems, diatoms are also rich in bioactive substances such as triacylglycerol and fucoxanthin. However, little is known about the transcriptional mechanisms underlying the biosynthesis of these substances. In this study, we found that the heat shock transcription factor PtHSF1 positively regulated the synthesis of triacylglycerol and fucoxanthin in Phaeodactylum tricornutum. Overexpression of PtHSF1 could increase the contents of triacylglycerol and fucoxanthin and upregulate key enzyme genes involved in the triacylglycerol and fucoxanthin biosynthesis pathways. On the other hand, gene silencing of PtHSF1 reduced the contents of triacylglycerol and fucoxanthin and the expression of the key enzyme genes involved in the triacylglycerol and fucoxanthin biosynthesis pathways. Further biochemical analysis revealed that PtHSF1 upregulated glycerol-2-phosphate acyltransferase 3 (GPAT3) and 1-deoxy-d-xylulose 5-phosphate synthase (DXS) by directly binding to their promoters, while genetic analysis demonstrated that PtHSF1 acted upstream of GPAT3 and DXS to regulate triacylglycerol and fucoxanthin synthesis. Therefore, in addition to elucidating the regulation mechanisms underlying PtHSF1-mediated triacylglycerol and fucoxanthin synthesis, this study also provided a candidate target for metabolic engineering of triacylglycerol and fucoxanthin in P. tricornutum.
    Materialart: Online-Ressource
    ISSN: 0032-0781 , 1471-9053
    RVK:
    Sprache: Englisch
    Verlag: Oxford University Press (OUP)
    Publikationsdatum: 2023
    ZDB Id: 2020758-X
    SSG: 12
    Standort Signatur Einschränkungen Verfügbarkeit
    BibTip Andere fanden auch interessant ...
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