The long-term responses of the photosynthetic proton circuit to drought

Kaori Kohzuma, Jeffrey A. Cruz, Kinya Akashi, Saki Hoshiyasu, Yuri Nakajima Munekage, Akiho Yokota, David M. Kramer

Research output: Contribution to journalArticlepeer-review

110 Citations (Scopus)


Proton motive force (pmf) across thylakoid membranes is not only for harnessing solar energy for photosynthetic CO2 fixation, but also for triggering feedback regulation of photosystem II antenna. The mechanisms for balancing these two roles of the proton circuit under the long-term environmental stress, such as prolonged drought, have been poorly understood. In this study, we report on the response of wild watermelon thylakoid 'proton circuit' to drought stress using both in vivo spectroscopy and molecular analyses of the representative photosynthetic components. Although drought stress led to enhanced proton flux via a ∼34% increase in cyclic electron flow around photosystem I (PS I), an observed ∼fivefold decrease in proton conductivity, gH+, across thylakoid membranes suggested that decreased ATP synthase activity was the major factor for sustaining elevated qE. Western blotting analyses revealed that ATP synthase content decreased significantly, suggesting that quantitative control of the complex plays a pivotal role in down-regulation of gH+. The expression level of cytochrome b6f complex - another key control point in photosynthesis - also declined, probably to prevent excess-reduction of PS I electron acceptors. We conclude that plant acclimation to long-term environmental stress involves global changes in the photosynthetic proton circuit, in which ATP synthase represents the key control point for regulating the relationship between electron transfer and pmf.

Original languageEnglish
Pages (from-to)209-219
Number of pages11
JournalPlant, Cell and Environment
Issue number3
Publication statusPublished - 2009 Mar
Externally publishedYes


  • ATP synthase
  • Cyclic electron transfer
  • Drought
  • Electrochromic shift
  • Non-photochemical quenching
  • Photoprotection
  • Photosynthesis
  • Proton motive force
  • qE
  • Wild watermelon (Citrullus lanatus)

ASJC Scopus subject areas

  • Physiology
  • Plant Science


Dive into the research topics of 'The long-term responses of the photosynthetic proton circuit to drought'. Together they form a unique fingerprint.

Cite this