Ccm1, a Regulatory Gene Controlling the Induction of a Carbon-Concentrating Mechanism in Chlamydomonas reinhardtii by Sensing CO2Availability

Aquatic photosynthetic organisms, including the green alga Chlamydomonas reinhardtii, induce a set of genes for a carbon-concentrating mechanism (CCM) to acclimate to CO2-limiting conditions. This acclimation is modulated by some mechanisms in the cell to sense CO2availability. Previously, a high-CO...

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Published inProceedings of the National Academy of Sciences - PNAS Vol. 98; no. 9; pp. 5347 - 5352
Main Authors Fukuzawa, Hideya, Miura, Kenji, Ishizaki, Kimitsune, Kucho, Ken-ichi, Saito, Tatsuaki, Kohinata, Tsutomu, Ohyama, Kanji
Format Journal Article
LanguageEnglish
Published National Academy of Sciences 24.04.2001
Subjects
Acclimatization
Biological Sciences
Carbon dioxide
Complementary DNA
DNA
Genes
Genetic mutation
Genomics
Messenger RNA
Proteins
RNA
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Summary:Aquatic photosynthetic organisms, including the green alga Chlamydomonas reinhardtii, induce a set of genes for a carbon-concentrating mechanism (CCM) to acclimate to CO2-limiting conditions. This acclimation is modulated by some mechanisms in the cell to sense CO2availability. Previously, a high-CO2-requiring mutant C16 defective in an induction of the CCM was isolated from C. reinhardtii by gene tagging. By using this pleiotropic mutant, we isolated a nuclear regulatory gene, Ccm1, encoding a 699-aa hydrophilic protein with a putative zinc-finger motif in its N-terminal region and a Gln repeat characteristic of transcriptional activators. Introduction of Ccm1 into this mutant restored an active carbon transport through the CCM, development of a pyrenoid structure in the chloroplast, and induction of a set of CCM-related genes. That a 5,128-base Ccm1 transcript and also the translation product of 76 kDa were detected in both high- and low-CO2conditions suggests that CCM1 might be modified posttranslationally. These data indicate that Ccm1 is essential to control the induction of CCM by sensing CO2availability in Chlamydomonas cells. In addition, complementation assay and identification of the mutation site of another pleiotropic mutant, cia5, revealed that His-54 within the putative zinc-finger motif of the CCM1 is crucial to its regulatory function.
ISSN:0027-8424
1091-6490