Physiological links among alternative electron transport pathways that reduce and oxidize plastoquinone in Arabidopsis

Yuki Okegawa, Yoshichika Kobayashi, Toshiharu Shikanai

Research output: Contribution to journalArticlepeer-review

68 Citations (Scopus)


In addition to linear electron transport from water to NADP+, alternative electron transport pathways are believed to regulate photosynthesis. In the two routes of photosystem I (PSI) cyclic electron transport, electrons are recycled from the stromal reducing pool to plastoquinone (PQ), generating additional ΔpH (proton gradient across thylakoid membranes). Plastid terminal oxidase (PTOX) accepts electrons from PQ and transfers them to oxygen to produce water. Although both electron transport pathways share the PQ pool, it is unclear whether they interact in vivo. To investigate the physiological link between PSI cyclic electron transport-dependent PQ reduction and PTOX-dependent PQ oxidation, we characterized mutants defective in both functions. Impairment of PSI cyclic electron transport suppressed leaf variegation in the Arabidopsis immutans (im) mutant, which is defective in PTOX. The im variegation was more effectively suppressed in the pgr5 mutant, which is defective in the main pathway of PSI cyclic electron transport, than in the crr2-2 mutant, which is defective in the minor pathway. In contrast to this chloroplast development phenotype, the im defect alleviated the growth phenotype of the crr2-2 pgr5 double mutant. This was accompanied by partial suppression of stromal over-reduction and restricted linear electron transport. We discuss the function of the alternative electron transport pathways in both chloroplast development and photosynthesis in mature leaves.

Original languageEnglish
Pages (from-to)458-468
Number of pages11
JournalPlant Journal
Issue number3
Publication statusPublished - Aug 2010
Externally publishedYes


  • chloroplast
  • immutans
  • plastid terminal oxidase
  • PSI cyclic electron transport
  • redox regulation
  • variegation

ASJC Scopus subject areas

  • Genetics
  • Plant Science
  • Cell Biology


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