The Cia5 gene controls formation of the carbon concentrating mechanism in Chlamydomonas reinhardtii.
Wild-type Chlamydomonas reinhardtii cells shifted from high concentrations (5%) of CO2 to low, ambient levels (0.03%) rapidly increase transcription of mRNAs from several CO2-responsive genes. Simultaneously, they develop a functional carbon concentrating mechanism that allows the cells to greatly increase internal levels of CO2 and HCO3-. The cia5 mutant is defective in all of these phenotypes. A newly isolated gene, designated Cia5, restores transformed cia5 cells to the phenotype of wild-type cells. The 6,481-bp gene produces a 5.1-kb mRNA that is present constitutively in light in high and low CO2 both in wild-type cells and the cia5 mutant. It encodes a protein that has features of a putative transcription factor and that, likewise, is present constitutively in low and high CO2 conditions. Complementation of cia5 can be achieved with a truncated Cia5 gene that is missing the coding information for 54 C-terminal amino acids. Unlike wild-type cells or cia5 mutants transformed with an intact Cia5 gene, cia5 mutants complemented with the truncated gene exhibit constitutive synthesis of mRNAs from CO2-responsive genes in light under both high and low CO2 conditions. These discoveries suggest that posttranslational changes to the C-terminal domain control the ability of CIA5 to act as an inducer and directly or indirectly control transcription of CO2-responsive genes. Thus, CIA5 appears to be a master regulator of the carbon concentrating mechanism and is intimately involved in the signal transduction mechanism that senses and allows immediate responses to fluctuations in environmental CO2 and HCO3- concentrations.
Xiang
Y
Y
Department of Biochemistry and School of Biological Sciences, University of Nebraska, Lincoln, NE 68588-0664, USA.
Zhang
J
J
Weeks
D P
DP
D021581:Active Transport, Cell Nucleus; D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D002244:Carbon / Q000378:metabolism*; D002245:Carbon Dioxide / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D016825:Chlamydomonas reinhardtii / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D004817:Epidermis / Q000378:metabolism; D005786:Gene Expression Regulation; D005816:Genetic Complementation Test; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D019697:Onions / Q000235:genetics; D010788:Photosynthesis / Q000235:genetics; D010940:Plant Proteins; D011506:Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D015800:Protozoan Proteins; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D014170:Transformation, Genetic
C425932:Cia5 protein, Chlamydomonas reinhardtii; D010940:Plant Proteins; D011506:Proteins; D015800:Protozoan Proteins; D012333:RNA, Messenger; D014157:Transcription Factors; D002245:Carbon Dioxide; D002244:Carbon