start-ver=1.4
cd-journal=joma
no-vol=11
cd-vols=
no-issue=44
article-no=
start-page=eaea6241
end-page=
dt-received=
dt-revised=
dt-accepted=
dt-pub-year=2025
dt-pub=20251031
dt-online=
en-article=
kn-article=
en-subject=
kn-subject=
en-title=
kn-title=Structural insights into the divergent evolution of a photosystem I supercomplex in Euglena gracilis
en-subtitle=
kn-subtitle=
en-abstract=
kn-abstract=Photosystem I (PSI) forms supercomplexes with light-harvesting complexes (LHCs) to perform oxygenic photosynthesis. Here, we report a 2.82-angstrom cryo?electron microscopy structure of the PSI-LHCI supercomplex from Euglena gracilis, a eukaryotic alga with secondary green alga-derived plastids. The structure reveals a PSI monomer core with eight subunits and 13 asymmetrically arranged LHCI proteins. Euglena LHCIs bind diadinoxanthin, which is one of the carotenoids typically associated with red-lineage LHCs and is not present in the canonical LHCI belt found in green-lineage PSI-LHCI structures. Phylogenetic analysis shows that the Euglena LHCIs originated from LHCII-related clades rather than from the green-lineage LHCI group and that the nuclear-encoded PSI subunit PsaD likely originated from cyanobacteria via horizontal gene transfer. These observations indicate a mosaic origin of the Euglena PSI-LHCI. Our findings uncover a noncanonical light-harvesting architecture and highlight the structural and evolutionary plasticity of photosynthetic systems, illustrating how endosymbiotic acquisition and lineage-specific adaptation shape divergent light-harvesting strategies.
en-copyright=
kn-copyright=

en-aut-name=KatoKoji
en-aut-sei=Kato
en-aut-mei=Koji
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=1
ORCID=

en-aut-name=NakajimaYoshiki
en-aut-sei=Nakajima
en-aut-mei=Yoshiki
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=2
ORCID=

en-aut-name=SakamotoRuna
en-aut-sei=Sakamoto
en-aut-mei=Runa
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=3
ORCID=

en-aut-name=KumazawaMinoru
en-aut-sei=Kumazawa
en-aut-mei=Minoru
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=4
ORCID=

en-aut-name=IfukuKentaro
en-aut-sei=Ifuku
en-aut-mei=Kentaro
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=5
ORCID=

en-aut-name=IshikawaTakahiro
en-aut-sei=Ishikawa
en-aut-mei=Takahiro
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=6
ORCID=

en-aut-name=ShenJian-Ren
en-aut-sei=Shen
en-aut-mei=Jian-Ren
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=7
ORCID=

en-aut-name=TakabayashiAtsushi
en-aut-sei=Takabayashi
en-aut-mei=Atsushi
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=8
ORCID=

en-aut-name=NagaoRyo
en-aut-sei=Nagao
en-aut-mei=Ryo
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=9
ORCID=

affil-num=1
en-affil=Research Institute for Interdisciplinary Science, Advanced Research Field, and Graduate School of Environmental, Life, Natural Science and Technology, Okayama University
kn-affil=

affil-num=2
en-affil=Research Institute for Interdisciplinary Science, Advanced Research Field, and Graduate School of Environmental, Life, Natural Science and Technology, Okayama University
kn-affil=

affil-num=3
en-affil=Research Institute for Interdisciplinary Science, Advanced Research Field, and Graduate School of Environmental, Life, Natural Science and Technology, Okayama University
kn-affil=

affil-num=4
en-affil=Institute of Low Temperature Science, Hokkaido University
kn-affil=

affil-num=5
en-affil=Graduate School of Agriculture, Kyoto University
kn-affil=

affil-num=6
en-affil=Institute of Agricultural and Life Sciences, Academic Assembly, Shimane University
kn-affil=

affil-num=7
en-affil=Research Institute for Interdisciplinary Science, Advanced Research Field, and Graduate School of Environmental, Life, Natural Science and Technology, Okayama University
kn-affil=

affil-num=8
en-affil=Institute of Low Temperature Science, Hokkaido University
kn-affil=

affil-num=9
en-affil=Faculty of Agriculture, Shizuoka University
kn-affil=
END