A mutant of Chlamydomonas reinhardtii that cannot acclimate to low CO2 conditions has an insertion in the Hdh1 gene

2005 ◽  
Vol 32 (1) ◽  
pp. 55 ◽  
Author(s):  
James E. Adams ◽  
Sergio L. Colombo ◽  
Catherine B. Mason ◽  
Ruby A. Ynalvez ◽  
Baran Tural ◽  
...  
Keyword(s):  
Chlamydomonas Reinhardtii ◽  
Inorganic Carbon ◽  
Single Copy ◽  
Wild Type ◽  
Poor Growth ◽  
Altered Expression ◽  
Haloacid Dehalogenase ◽  
Low Co2 ◽  
Photosynthetic Microorganisms ◽  
Zeocin Resistance

Photosynthetic microorganisms must acclimate to environmental conditions, such as low CO2 environments or high light intensities, which may lead to photo-oxidative stress. In an effort to understand how photosynthetic microorganisms acclimate to these conditions, Chlamydomonas reinhardtii was transformed using the BleR cassette, selected for Zeocin resistance and screened for colonies that showed poor growth at low CO2 levels. One of the insertional mutants obtained, named slc-230, was shown to have a BleR insert in the first exon of Hdh1, a novel, single copy gene. The predicted Hdh1 gene product has similarity to bacterial haloacid dehalogenase-like proteins, a protein family that includes phosphatases and epoxide hydrolases. In addition, Hdh1 is predicted to be localised to the chloroplast or mitochondria in C. reinhardtii. It was found that a genomic copy of wild type Hdh1 can complement slc-230. Physiological studies were conducted to determine the effects of the altered expression of Hdh1 in slc-230. slc-230 grows slowly autotrophically in low CO2, exhibits a lower affinity for inorganic carbon, a decreasing photosynthetic rate over time and a lower content of chlorophylls and quenching xanthophylls than wild type cells. Some possible roles of Hdh1 in the acclimation to low CO2 conditions are discussed.

Identification and characterisation of a novel inorganic carbon acquisition gene, CIA7, from an insertional mutant of Chlamydomonas reinhardtii

2008 ◽  
Vol 35 (5) ◽  
pp. 373 ◽  
Author(s):  
Ruby A. Ynalvez ◽  
James V. Moroney
Keyword(s):  
Chlamydomonas Reinhardtii ◽  
Metal Ion ◽  
Inorganic Carbon ◽  
Antibiotic Resistance Gene ◽  
Inverse Pcr ◽  
Chloroplast Targeting ◽  
Calculated Molecular Mass ◽  
Prediction Program ◽  
Metal Transporter ◽  
Low Co2

Chlamydomonas reinhardtii is a unicellular eukaryotic alga which possesses a CO2-concentrating mechanism (CCM) that enables it to grow at low CO2 concentrations. Previously, insertional mutants were generated to enable isolation of inorganic carbon transporters and other proteins that might be essential for a functional CCM. These mutants have an antibiotic resistance gene that encodes a protein that binds to Zeocin inhibiting Zeocin’s DNA strand cleavage activity. The DNA flanking the BleR insert of one of the high CO2 requiring strains, named cia7, was cloned with inverse-PCR and sequenced. Sequence analysis showed homology to conserved bacterial proteins of unknown function, but there were no ESTs in this region of the genome. However, the presence of a gene was established by PCR and RLM-RACE. CIA7 was found to have four exons and the BleR insert was in the fourth exon. CIA7 encodes a protein of 104 amino acids with a calculated molecular mass of 11.3 kDa. Based on the ChloroP prediction program, the protein is predicted to have a chloroplast targeting signal. Complementation analyses results showed possible partially rescued mutants, and RNAi showed several transformants with a sick on low CO2 phenotype with reduced expression of CIA7. These results suggest that CIA7 is a gene that facilitates growth in C. reinhardtii under low CO2 conditions. One possible role of CIA7 would be in the delivery or storage of a metal ion. It may play a potential role as either a domain of a metal transporter or as a metallochaperone.

Adaptation of a Chlamydomonas mutant with reduced rate of photorespiration to different concentrations of CO2

2005 ◽  
Vol 83 (7) ◽  
pp. 834-841 ◽  
Author(s):  
Kensaku Suzuki ◽  
Hidenori Onodera
Keyword(s):  
Chlorophyll Fluorescence ◽  
Chlamydomonas Reinhardtii ◽  
Inorganic Carbon ◽  
Electron Flow ◽  
Effective Quantum Yield ◽  
Wild Type ◽  
Chlorophyll Fluorescence Parameters ◽  
Phosphoglycolate Phosphatase ◽  
Concentrating Mechanism ◽  
Type Strains

It has been widely accepted that Chlamydomonas reinhardtii cells utilize inorganic carbon very efficiently for photosynthesis by operating a CO2-concentrating mechanism (CCM) under conditions of limited CO2. To help define the mechanism, 7FR2N, one of the suppressor double mutants of phosphoglycolate phosphatase-deficient (pgp1) mutants that have a reduced photorespiration rate (RPR) was crossed with wild-type strains to generate the strain N21 as a single RPR mutant. The comparison of photosynthetic characteristics with wild-type strains after the cells adapted to different concentrations of CO2 revealed that photosynthetic affinity for inorganic carbon was higher than that in wild-type strains after adaptation to concentrations between 50 µL·L–1 CO2 and 5% CO2. Chlorophyll fluorescence parameters were also compared, and the biggest difference between N21 and the wild-type strains was observed in the photochemical quenching and effective quantum yield of photosystem II (ΔF/Fm′) at the CO2 compensation point. These values in N21 increased in a similar manner to the photosynthetic affinity for CO2, and increased significantly when the cells adapted to low-CO2 levels, whereas the values in the wild-type strains were apparently lower without any significant changes, regardless of the CO2 concentrations to which they were adapted. Although it was not clear if a nonphotochemical quenching parameter (NPQ) in N21 was higher than that in wild-type strains, NPQ increased coincidentally with the increase in photosynthetic affinity for inorganic carbon when the CO2 concentrations to which the strains were adapted decreased, in both the mutant and wild-type strain, suggesting that this form of NPQ reflects the operation of CCM in certain conditions. Possible candidates for the RPR mutation and the relationship between CCM and photosynthetic electron flow are discussed.Key words: Chlamydomonas reinhardtii, chlorophyll fluorescence, CO2-concentrating mechanism, low-CO2 responsive gene, phosphoglycolate phosphatase, photorespiration.

scholarly journals Expression of a Low CO2–Inducible Protein, LCI1, Increases Inorganic Carbon Uptake in the Green Alga Chlamydomonas reinhardtii

2010 ◽  
Vol 22 (9) ◽  
pp. 3105-3117 ◽  
Author(s):  
Norikazu Ohnishi ◽  
Bratati Mukherjee ◽  
Tomoki Tsujikawa ◽  
Mari Yanase ◽  
Hirobumi Nakano ◽  
...  
Keyword(s):  
Chlamydomonas Reinhardtii ◽  
Green Alga ◽  
Inorganic Carbon ◽  
Carbon Uptake ◽  
Low Co2 ◽  
Inducible Protein ◽  
Inorganic Carbon Uptake

scholarly journals The Entner-Doudoroff Pathway Contributes to Glycogen Breakdown During High to Low CO2 Shifts in the Cyanobacterium Synechocystis sp. PCC 6803

2021 ◽  
Vol 12 ◽  
Author(s):  
Stefan Lucius ◽  
Alexander Makowka ◽  
Klaudia Michl ◽  
Kirstin Gutekunst ◽  
Martin Hagemann
Keyword(s):  
Organic Compounds ◽  
Inorganic Carbon ◽  
Pentose Phosphate ◽  
Oxygenic Photosynthesis ◽  
Wild Type ◽  
Low Co2 ◽  
Glycogen Breakdown ◽  
Synechocystis Sp ◽  
Mutant Collection ◽  
Pcc 6803

Cyanobacteria perform plant-like oxygenic photosynthesis to convert inorganic carbon into organic compounds and can also use internal carbohydrate reserves under specific conditions. A mutant collection with defects in different routes for sugar catabolism was studied to analyze which of them is preferentially used to degrade glycogen reserves in light-exposed cells of Synechocystis sp. PCC 6803 shifted from high to low CO2 conditions. Mutants defective in the glycolytic Embden–Meyerhof–Parnas pathway or in the oxidative pentose-phosphate (OPP) pathway showed glycogen levels similar to wild type under high CO2 (HC) conditions and were able to degrade it similarly after shifts to low CO2 (LC) conditions. In contrast, the mutant Δeda, which is defective in the glycolytic Entner-Doudoroff (ED) pathway, accumulated elevated glycogen levels under HC that were more slowly consumed during the LC shift. In consequence, the mutant Δeda showed a lowered ability to respond to the inorganic carbon shifts, displayed a pronounced lack in the reactivation of growth when brought back to HC, and differed significantly in its metabolite composition. Particularly, Δeda accumulated enhanced levels of proline, which is a well-known metabolite to maintain redox balances via NADPH levels in many organisms under stress conditions. We suggest that deletion of eda might promote the utilization of the OPP shunt that dramatically enhance NADPH levels. Collectively, the results point at a major regulatory contribution of the ED pathway for the mobilization of glycogen reserves during rapid acclimation to fluctuating CO2 conditions.

Sign in / Sign up

Export Citation Format

Share Document