Analyses of CIA5, the master regulator of the carbon-concentrating mechanism in Chlamydomonas reinhardtii, and its control of gene expression

Abstract

In numerous studies, the CIA5 gene of Chlamydomonas reinhardtii Dangeard has been shown to control the expression of several "CO2-responsive genes" when cells are shifted to higher or lower levels of CO2. Using DNA microarray analyses with arrays containing 2764 unique cDNA sequences, we have demonstrated that several additional genes are controlled by the CIA5 gene, some increasing in expression when CO2 levels are lowered and others decreasing. Not all genes that respond to changes in CO2 concentrations are controlled by CIA5. For example, the RH1 gene, is markedly induced when both wild-type and cia5 mutant cells are shifted to high levels of CO2. We demonstrate that cycloheximide (an inhibitor of cytoplasmic protein synthesis) has no apparent effect on the initial induction of CO2-responsive genes, suggesting constitutive presence of all the molecular machinery needed by the cell to immediately respond to changes in CO2 levels. This observation is consistent with our earlier suggestions that CIA5 or another key component(s) of the carbon-concentrating mechanism must be rapidly "activated" (or "inactivated") as part of the response of C. reinhardtii to changes in external CO2 levels. We present new, direct evidence that CIA5 is localized to the nucleus in both low- and high-CO2 conditions.Key words: CIA5, CCM, carbon-concentrating mechanism, photosynthesis, gene regulation, Chlamydomonas reinhardtii, CO2.

Transcriptome-Wide Changes in Chlamydomonas reinhardtii Gene Expression Regulated by Carbon Dioxide and the CO2-Concentrating Mechanism Regulator CIA5/CCM1

“…classic LCI genes reported previously (Chen et al, 1996;Somanchi and Moroney, 1999;Miura et al, 2004;Wang et al, 2005;Wang and Spalding, 2006;Yamano and Fukuzawa, 2009). We selected 106 of these previously reported LCI genes for a direct comparison with genes identified as having a C-effect or CS-effect.…”

“…Because of the interest in the CCM specifically, at least 106 genes have been reported as LCI genes, many of which also reportedly require CIA5 for differential expression (Chen et al, 1996;Somanchi and Moroney, 1999;Miura et al, 2004;Wang et al, 2005;Wang and Spalding, 2006;Yamano and Fukuzawa, 2009). Some of these LCI genes, such as CAH3, LCI1, LCIA, LCIB, and HLA3, reportedly play important roles in the C. reinhardtii CCM (Galván et al, 2002;Wang and Spalding, 2006;Duanmu et al, 2009aDuanmu et al, , 2009bOhnishi et al, 2010), and the function of others, such as CCP1, CCP2, and LCIC, in the CCM also has been implicated (Pollock et al, 2004;Wang and Spalding, 2006;Yamano et al, 2010).…”

SUMOylation by a Stress-Specific Small Ubiquitin-Like Modifier E2 Conjugase Is Essential for Survival ofChlamydomonas reinhardtiiunder Stress Conditions

“…A 1:1,000 dilution of the third bleed was used for detection of SUMO proteins. Antibodies to inorganic carbon accumulation mutant5 protein have been previously described (Wang et al, 2005) and were used at a 1:10,000 dilution. Secondary antibody for anti-SUMO and anti-Cia5 primary antibodies were HRP-linked donkey anti-rabbit Igs used at a 1:10,000 dilution.…”

Proposed Carbon Dioxide Concentrating Mechanism in Chlamydomonas reinhardtii

“…In addition, when RH1 expression is reduced by mutation, C. reinhardtii can still grow on low levels of CO 2 but shows reduced growth on elevated levels of CO 2 (87). Likewise, RH1 is not regulated by CIA5 (101). The possible physiological role of this protein is to facilitate CO 2 entry into the cell when the CO 2 level is high.…”