Conserved role of PROTON GRADIENT REGULATION 5 in the regulation of PSI cyclic electron transport

Terri A. Long, Yuki Okegawa, Toshiharu Shikanai, Gregory W. Schmidt, Sarah F. Covert

Research output: Contribution to journalArticlepeer-review

22 Citations (Scopus)


There are at least two photosynthetic cyclic electron transport (CET) pathways in most C3 plants: the NAD(P)H dehydrogenase (NDH)-dependent pathway and a pathway dependent upon putative ferredoxin:plastoquinone oxidoreductase (FQR) activity. While the NDH complex has been identified, and shown to play a role in photosynthesis, especially under stress conditions, less is known about the machinery of FQR-dependent CET. Recent studies indicate that FQR-dependent CET is dependent upon PGR5, a small protein of unknown function. In a previous study we found that overexpression of PGR5 causes alterations in growth and development associated with decreased chloroplast development and a transient increase in nonphotochemical quenching (NPQ) after the shift from dark to light. In the current study we examine the spatiotemporal expression pattern of PGR5, and the effects of overexpression of PGR5 in Arabidopsis under a host of light and stress conditions. To investigate the conserved function of PGR5, we cloned PGR5 from a species which apparently lacks NDH, loblolly pine, and overexpressed it in Arabidopsis. Although greening of cotyledons was severely delayed in overexpressing lines under low light, mature plants survived exposure to high light and drought stress better than wild-type. In addition, PSI was more resistant to high light in the PGR5 overexpressors than in wild-type plants, while PSII was more sensitive to this stress. These complex responses corresponded to alterations in linear and cyclic electron transfer, suggesting that over-accumulation of PGR5 induces pleiotropic effects, probably via elevated CET. We conclude that PGR5 has a developmentally-regulated, conserved role in mediating CET.

Original languageEnglish
Pages (from-to)907-918
Number of pages12
Issue number6
Publication statusPublished - Nov 2008
Externally publishedYes


  • Arabidopsis
  • Cyclic electron transport
  • Nonphotochemical quenching
  • PGR5
  • Photosynthesis
  • Stress tolerance

ASJC Scopus subject areas

  • Genetics
  • Plant Science


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