Isolation and characterization of high-CO2 requiring mutants from Chlamydomonas reinhardtii by gene tagging

1998 ◽  
Vol 76 (6) ◽  
pp. 1092-1097 ◽  
Author(s):  
Hideya Fukuzawa ◽  
Kimitsune Ishizaki ◽  
Kenji Miura ◽  
Shoji Matsueda ◽  
Tatsuya Ino-ue ◽  
...  
Keyword(s):  
Carbonic Anhydrase ◽  
Nitrate Reductase ◽  
Chlamydomonas Reinhardtii ◽  
Insertional Mutagenesis ◽  
Class Ii ◽  
Gene Tagging ◽  
Carbon Concentrating Mechanism ◽  
Isolation And Characterization ◽  
Concentrating Mechanism ◽  
Carbonic Anhydrase Gene

To isolate genes essential to the carbon concentrating mechanism and the CO2-signal transduction mechanisms, seven high-CO2 requiring mutants were isolated from Chlamydomonas reinhardtii by the insertion of nit1 gene encoding nitrate reductase. These mutants were grouped into two classes. Class I contains mutants that show a severe CO2-requiring phenotype (C1 and C3). Class II includes those with a moderate CO2-requiring phenotype (C2, C5, C7, C15, and C16). One of the class II mutants, C5, appeared to be defective in the utilization of intracellularly accumulated inorganic carbon. On the other hand, the mutant C16 appeared to be defective not only in the uptake of carbon but also in the induction of the periplasmic carbonic anhydrase gene, CAH1, as well as in the development of pyrenoid structure under low-CO2 conditions. These mutations in C5 and C16 mutants appeared to be caused by single insertional events of the introduced DNA fragment into the genomic DNA, suggesting that their corresponding genes could be tagged using the nit1 gene.Key words: carbon concentrating mechanism, carbonic anhydrase, gene tagging, insertional mutagenesis, nitrate reductase.

The carbonic anhydrase gene families of Chlamydomonas reinhardtii

2005 ◽  
Vol 83 (7) ◽  
pp. 780-795 ◽  
Author(s):  
Mautusi Mitra ◽  
Catherine B Mason ◽  
Ying Xiao ◽  
Ruby A Ynalvez ◽  
Scott M Lato ◽  
...  
Keyword(s):  
Carbonic Anhydrase ◽  
Chlamydomonas Reinhardtii ◽  
Gene Families ◽  
Carbonic Anhydrases ◽  
Photosynthetic Organisms ◽  
Surrounding Environment ◽  
Concentrating Mechanism ◽  
Chloroplast Stroma ◽  
Carbonic Anhydrase Gene

Carbonic anhydrases (CAs) are zinc-containing metalloenzymes that catalyze the reversible interconversion of CO2 and HCO3–. Aquatic photosynthetic organisms have evolved different forms of CO2-concentrating mechanisms to aid Rubisco in capturing CO2 from the surrounding environment. One aspect of all CO2-concentrating mechanisms is the critical roles played by various specially localized extracellular and intracellular CAs. There are three evolutionarily unrelated CA families designated α-, β-, and γ-CA. In the green alga, Chlamydomonas reinhardtii Dangeard, eight CAs have now been identified, including three α-CAs and five β-CAs. In addition, C. reinhardtii has another CA-like gene, Glp1 that is similar to known γ-CAs. To characterize these different CA isoforms, some of the CA genes have been overexpressed to determine whether the proteins have CA activity and to generate antibodies for in vivo immunolocalization. The CA proteins Cah3, Cah6, and Cah8, and the γ-CA-like protein, Glp1, have been overexpressed. Cah3, Cah6, and Cah8 have CA activity, but Glp1 does not. At least two of these proteins, Cah3 and Cah6, are localized to the chloroplast. Using immunolocalization and sequence analyses, we have determined that Cah6 is located to the chloroplast stroma and confirmed that Cah3 is localized to the chloroplast thylakoid lumen. Activity assays show that Cah3 is 100 times more sensitive to sulfonamides than Cah6. We present a model on how these two chloroplast CAs might participate in the CO2-concentrating mechanism of C. reinhardtii. Key words: carbonic anhydrase, CO2-concentrating mechanism, Chlamydomonas, immunolocalization.

scholarly journals The Induction of Pyrenoid Synthesis by Hyperoxia and its Implications for the Natural Diversity of Photosynthetic Responses in Chlamydomonas

2021 ◽  
Author(s):  
Peter Neofotis ◽  
Joshua Temple ◽  
Oliver L. Tessmer ◽  
Jacob Bibik ◽  
Nicole Norris ◽  
...  
Keyword(s):  
Chlamydomonas Reinhardtii ◽  
Genetic Variations ◽  
Carbon Concentrating Mechanism ◽  
Concentrating Mechanism ◽  
Show Evidence ◽  
Natural Diversity ◽  
Photosynthetic Responses

ABSTRACTIn algae, it is well established that the pyrenoid, a component of the carbon-concentrating mechanism (CCM), is essential for efficient photosynthesis at low CO2. However, the signal that triggers the formation of the pyrenoid has remained elusive. Here, we show that, in Chlamydomonas reinhardtii, the pyrenoid is strongly induced by hyperoxia, even at high CO2 or bicarbonate levels. These results suggest that the pyrenoid can be induced by a common product of photosynthesis specific to low CO2 or hyperoxia. Consistent with this view, the photorespiratory by-product, H2O2, induced the pyrenoid, suggesting that it acts as a signal. Finally, we show evidence for linkages between genetic variations in hyperoxia tolerance, H2O2 signaling, and pyrenoid morphologies.

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