Identification and characterization of a stable intermediate in photosystem I assembly in tobacco.
Photosystem I (PSI) is the most efficient bioenergetic nanomachine in nature and one of the largest membrane protein complexes known. It is composed of 18 protein subunits that bind more than 200 co-factors and prosthetic groups. While the structure and function of PSI have been studied in great detail, very little is known about the PSI assembly process. In this work, we have characterized a PSI assembly intermediate in tobacco plants, which we named PSI*. We found PSI* to contain only a specific subset of the core subunits of PSI. PSI* is particularly abundant in young leaves where active thylakoid biogenesis takes place. Moreover, PSI* was found to overaccumulate in PsaF-deficient mutant plants, and we show that re-initiation of PsaF synthesis promotes the maturation of PSI* into PSI. The attachment of antenna proteins to PSI also requires the transition from PSI* to mature PSI. Our data could provide a biochemical entry point into the challenging investigation of PSI biogenesis and allow us to improve the model for the assembly pathway of PSI in thylakoid membranes of vascular plants.
Max-Planck-Institut für Molekulare Pflanzenphysiologie, Am Mühlenberg 1, D-14476, Potsdam-Golm, Germany.
Gal
http://orcid.org/0000-0003-1037-0040
G
Wittenberg
Department of Biochemistry, Molecular Plant Biology, University of Turku, FI-20014, Turku, Finland.
Sari
S
Järvi
Max-Planck-Institut für Molekulare Pflanzenphysiologie, Am Mühlenberg 1, D-14476, Potsdam-Golm, Germany.
Marta
M
Hojka
Max-Planck-Institut für Molekulare Pflanzenphysiologie, Am Mühlenberg 1, D-14476, Potsdam-Golm, Germany.
Szilvia Z
SZ
Tóth
Max-Planck-Institut für Molekulare Pflanzenphysiologie, Am Mühlenberg 1, D-14476, Potsdam-Golm, Germany.
Etienne H
http://orcid.org/0000-0003-4712-9824
EH
Meyer
Department of Biochemistry, Molecular Plant Biology, University of Turku, FI-20014, Turku, Finland.
Eva-Mari
EM
Aro
Max-Planck-Institut für Molekulare Pflanzenphysiologie, Am Mühlenberg 1, D-14476, Potsdam-Golm, Germany.
Mark A
MA
Schöttler
Max-Planck-Institut für Molekulare Pflanzenphysiologie, Am Mühlenberg 1, D-14476, Potsdam-Golm, Germany.
Ralph
R
Bock
D010788:Photosynthesis / Q000235:genetics / Q000502:physiology; D045331:Photosystem I Protein Complex / Q000235:genetics / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D020524:Thylakoids / Q000378:metabolism; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism*
D045331:Photosystem I Protein Complex; D010940:Plant Proteins
photosynthesis; photosystem assembly; photosystem biogenesis; thylakoid membrane