TY - JOUR
T1 - Chloroplast ATP synthase modulation of the thylakoid proton motive force
T2 - implications for photosystem I and photosystem II photoprotection
AU - Kanazawa, Atsuko
AU - Ostendorf, Elisabeth
AU - Kohzuma, Kaori
AU - Hoh, Donghee
AU - Strand, Deserah D.
AU - Sato-Cruz, Mio
AU - Savage, Linda
AU - Cruz, Jeffrey A.
AU - Fisher, Nicholas
AU - Froehlich, John E.
AU - Kramer, David M.
N1 - Funding Information:
We thank Prof. Donald Ort for providing the cfq seeds and for interesting discussions, Prof. Alice Barkan (Institute of Molecular Biology/Department of Biology, University of Oregon) for the AtpB and Cytochrome f antibodies, Prof. Kinya Akashi (Agricultural Plant Science, Molecular Biology, Tottori University) for the AtpE antibody. We also thank Dr. Douglas Whitten for his assistance at the MSU Proteomics facility, and Mr. Geoffrey Davis for the stimulating discussions.
Publisher Copyright:
© 2017 Kanazawa, Ostendorf, Kohzuma, Hoh, Strand, Sato-Cruz, Savage, Cruz, Fisher, Froehlich and Kramer.
PY - 2017/5/3
Y1 - 2017/5/3
N2 - In wild type plants, decreasing CO2 lowers the activity of the chloroplast ATP synthase, slowing proton efflux from the thylakoid lumen resulting in buildup of thylakoid proton motive force (pmf). The resulting acidification of the lumen regulates both light harvesting, via the qE mechanism, and photosynthetic electron transfer through the cytochrome b6 f complex. Here, we show that the cfq mutant of Arabidopsis, harboring single point mutation in its γ-subunit of the chloroplast ATP synthase, increases the specific activity of the ATP synthase and disables its down-regulation under low CO2. The increased thylakoid proton conductivity (gH+) in cfq results in decreased pmf and lumen acidification, preventing full activation of qE and more rapid electron transfer through the b6 f complex, particularly under low CO2 and fluctuating light. These conditions favor the accumulation of electrons on the acceptor side of PSI, and result in severe loss of PSI activity. Comparing the current results with previous work on the pgr5 mutant suggests a general mechanism where increased PSI photodamage in both mutants is caused by loss of pmf, rather than inhibition of CEF per se. Overall, our results support a critical role for ATP synthase regulation in maintaining photosynthetic control of electron transfer to prevent photodamage.
AB - In wild type plants, decreasing CO2 lowers the activity of the chloroplast ATP synthase, slowing proton efflux from the thylakoid lumen resulting in buildup of thylakoid proton motive force (pmf). The resulting acidification of the lumen regulates both light harvesting, via the qE mechanism, and photosynthetic electron transfer through the cytochrome b6 f complex. Here, we show that the cfq mutant of Arabidopsis, harboring single point mutation in its γ-subunit of the chloroplast ATP synthase, increases the specific activity of the ATP synthase and disables its down-regulation under low CO2. The increased thylakoid proton conductivity (gH+) in cfq results in decreased pmf and lumen acidification, preventing full activation of qE and more rapid electron transfer through the b6 f complex, particularly under low CO2 and fluctuating light. These conditions favor the accumulation of electrons on the acceptor side of PSI, and result in severe loss of PSI activity. Comparing the current results with previous work on the pgr5 mutant suggests a general mechanism where increased PSI photodamage in both mutants is caused by loss of pmf, rather than inhibition of CEF per se. Overall, our results support a critical role for ATP synthase regulation in maintaining photosynthetic control of electron transfer to prevent photodamage.
KW - ATP synthase
KW - PSI
KW - PSII
KW - Photoprotection
KW - Pmf
KW - Proton motive force
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U2 - 10.3389/fpls.2017.00719
DO - 10.3389/fpls.2017.00719
M3 - Article
AN - SCOPUS:85018860348
VL - 8
JO - Frontiers in Plant Science
JF - Frontiers in Plant Science
SN - 1664-462X
M1 - 719
ER -