The Chlamydomonas reinhardtii cia3 mutant lacking a thylakoid lumen-localized carbonic anhydrase is limited by CO2 supply to Rubisco and not photosystem II function in vivo

David Thomas Hanson, Linda A. Franklin, Goran Samuelsson, Murray R. Badger*

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    71 Citations (Scopus)

    Abstract

    The Chlamydomonas reinhardtii cia3 mutant has a phenotype indicating that it requires high-CO2 levels for effective photosynthesis and growth. It was initially proposed that this mutant was defective in a carbonic anhydrase (CA) that was a key component of the photosynthetic CO 2-concentrating mechanism (CCM). However, more recent identification of the genetic lesion as a defect in a lumenal CA associated with photosystem II (PSII) has raised questions about the role of this CA in either the CCM or PSII function. To resolve the role of this lumenal CA, we re-examined the physiology of the cia3 mutant. We confirmed and extended previous gas exchange analyses by using membrane-inlet mass spectrometry to monitor 16O2, 18O2, and CO2 fluxes in vivo. The results demonstrate that PSII electron transport is not limited in the cia3 mutant at low inorganic carbon (Ci). We also measured metabolite pools sizes and showed that the RuBP pool does not fall to abnormally low levels at low Ci as might be expected by a photosynthetic electron transport or ATP generation limitation. Overall, the results demonstrate that under low Ci conditions, the mutant lacks the ability to supply Rubisco with adequate CO2 for effective CO2 fixation and is not limited directly by any aspect of PSII function. We conclude that the thylakoid CA is primarily required for the proper functioning of the CCM at low Ci by providing an ample supply of CO2 for Rubisco.

    Original languageEnglish
    Pages (from-to)2267-2275
    Number of pages9
    JournalPlant Physiology
    Volume132
    Issue number4
    DOIs
    Publication statusPublished - 1 Aug 2003

    Fingerprint

    Dive into the research topics of 'The Chlamydomonas reinhardtii cia3 mutant lacking a thylakoid lumen-localized carbonic anhydrase is limited by CO2 supply to Rubisco and not photosystem II function in vivo'. Together they form a unique fingerprint.

    Cite this