scholarly journals Photoinhibition and continuous growth of the wild-type and a high-light tolerant strain of Chlamydomonas reinhardtii

2019 ◽  
Vol 57 (2) ◽  
pp. 617-626 ◽  
Author(s):  
O. VIRTANEN ◽  
D. VALEV ◽  
O. KRUSE ◽  
L. WOBBE ◽  
E. TYYSTJARVI
Keyword(s):  
Chlamydomonas Reinhardtii ◽  
High Light ◽  
Wild Type ◽  
Continuous Growth ◽  
Tolerant Strain

scholarly journals The non-photochemical quenching protein LHCSR3 prevents oxygen-dependent photoinhibition in Chlamydomonas reinhardtii

2020 ◽  
Vol 71 (9) ◽  
pp. 2650-2660 ◽  
Author(s):  
Thomas Roach ◽  
Chae Sun Na ◽  
Wolfgang Stöggl ◽  
Anja Krieger-Liszkay
Keyword(s):  
Chlamydomonas Reinhardtii ◽  
Colony Growth ◽  
High Light ◽  
Photochemical Quenching ◽  
Oxygen Species ◽  
Wild Type ◽  
Psii Activity ◽  
High O2 ◽  
Non Photochemical Quenching ◽  
Repair Cycle

Abstract Non-photochemical quenching (NPQ) helps dissipate surplus light energy, preventing formation of reactive oxygen species (ROS). In Chlamydomonas reinhardtii, the thylakoid membrane protein LHCSR3 is involved in pH-dependent (qE-type) NPQ, lacking in the npq4 mutant. Preventing PSII repair revealed that npq4 lost PSII activity faster than the wild type (WT) in elevated O2, while no difference between strains was observed in O2-depleted conditions. Low Fv/Fm values remained 1.5 h after moving cells out of high light, and this qH-type quenching was independent of LHCSR3 and not accompanied by losses of maximum PSII activity. Culturing cells in historic O2 atmospheres (30–35%) increased the qE of cells, due to increased LHCSR1 and PsbS levels, and LHCSR3 in the WT, showing that atmospheric O2 tensions regulate qE capacity. Colony growth of npq4 was severely restricted at elevated O2, and npq4 accumulated more reactive electrophile species (RES) than the WT, which could damage PSI. Levels of PsaA (PSI) were lower in npq4 grown at 35% O2, while PsbA (PSII) levels remained stable. We conclude that even at high O2 concentrations, the PSII repair cycle is sufficient to maintain net levels of PSII. However, LHCSR3 has an important function in protecting PSI against O2-mediated damage, such as via RES.

scholarly journals Acclimation of Chlamydomonas reinhardtii to extremely strong light

2020 ◽  
Vol 147 (1) ◽  
pp. 91-106
Author(s):  
Olli Virtanen ◽  
Sergey Khorobrykh ◽  
Esa Tyystjärvi
Keyword(s):  
Chlamydomonas Reinhardtii ◽  
Photosynthetic Photon Flux Density ◽  
High Light ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Wild Type ◽  
Strong Light ◽  
Photosynthetic Organisms ◽  
Arrhenius Factor ◽  
And Control

AbstractMost photosynthetic organisms are sensitive to very high light, although acclimation mechanisms enable them to deal with exposure to strong light up to a point. Here we show that cultures of wild-type Chlamydomonas reinhardtii strain cc124, when exposed to photosynthetic photon flux density 3000 μmol m−2 s−1 for a couple of days, are able to suddenly attain the ability to grow and thrive. We compared the phenotypes of control cells and cells acclimated to this extreme light (EL). The results suggest that genetic or epigenetic variation, developing during maintenance of the population in moderate light, contributes to the acclimation capability. EL acclimation was associated with a high carotenoid-to-chlorophyll ratio and slowed down PSII charge recombination reactions, probably by affecting the pre-exponential Arrhenius factor of the rate constant. In agreement with these findings, EL acclimated cells showed only one tenth of the 1O2 level of control cells. In spite of low 1O2 levels, the rate of the damaging reaction of PSII photoinhibition was similar in EL acclimated and control cells. Furthermore, EL acclimation was associated with slow PSII electron transfer to artificial quinone acceptors. The data show that ability to grow and thrive in extremely strong light is not restricted to photoinhibition-resistant organisms such as Chlorella ohadii or to high-light tolerant mutants, but a wild-type strain of a common model microalga has this ability as well.

Molecular Markers for Rapidly Identifying Candidate Genes in Chlamydomonas reinhardtii: ERY1 and ERY2 Encode Chloroplast Ribosomal Proteins

Genetics ◽  
2003 ◽  
Vol 164 (4) ◽  
pp. 1345-1353
Author(s):  
Amber K Bowers ◽  
Jennifer A Keller ◽  
Susan K Dutcher
Keyword(s):  
Molecular Markers ◽  
Chlamydomonas Reinhardtii ◽  
Candidate Genes ◽  
Splice Site ◽  
Genomic Dna ◽  
Ribosomal Proteins ◽  
Genomic Sequence ◽  
Point Mutations ◽  
Acceptor Site ◽  
Wild Type

Abstract To take advantage of available expressed sequence tags and genomic sequence, we have developed 64 PCR-based molecular markers in Chlamydomonas reinhardtii that map to the 17 linkage groups. These markers will allow the rapid association of a candidate gene sequence with previously identified mutations. As proof of principle, we have identified the genes encoded by the ERY1 and ERY2 loci. Mendelian mutations that confer resistance to erythromycin define three unlinked nuclear loci in C. reinhardtii. Candidate genes ribosomal protein L4 (RPL4) and L22 (RPL22) are tightly linked to the ERY1 locus and ERY2 locus, respectively. Genomic DNA for RPL4 from wild type and five mutant ery1 alleles was amplified and sequenced and three different point mutations were found. Two different glycine residues (G102 and G112) are replaced by aspartic acid and both are in the unstructured region of RPL4 that lines the peptide exit tunnel of the chloroplast ribosome. The other two alleles change a splice site acceptor site. Genomic DNA for RPL22 from wild type and three mutant ery2 alleles was amplified and sequenced and revealed three different point mutations. Two alleles have premature stop codons and one allele changes a splice site acceptor site.

Crystal structure of the wild-type and D30A mutant thioredoxin h of Chlamydomonas reinhardtii and implications for the catalytic mechanism

2001 ◽  
Vol 359 (1) ◽  
pp. 65-75 ◽  
Author(s):  
Valeria MENCHISE ◽  
Catherine CORBIER ◽  
Claude DIDIERJEAN ◽  
Michele SAVIANO ◽  
Ettore BENEDETTI ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Proton Transfer ◽  
Chlamydomonas Reinhardtii ◽  
Catalytic Mechanism ◽  
Structural Data ◽  
Careful Analysis ◽  
Wild Type ◽  
Thioredoxin H ◽  
Dynamics Simulations

Thioredoxins are ubiquitous proteins which catalyse the reduction of disulphide bridges on target proteins. The catalytic mechanism proceeds via a mixed disulphide intermediate whose breakdown should be enhanced by the involvement of a conserved buried residue, Asp-30, as a base catalyst towards residue Cys-39. We report here the crystal structure of wild-type and D30A mutant thioredoxin h from Chlamydomonas reinhardtii, which constitutes the first crystal structure of a cytosolic thioredoxin isolated from a eukaryotic plant organism. The role of residue Asp-30 in catalysis has been revisited since the distance between the carboxylate OD1 of Asp-30 and the sulphur SG of Cys-39 is too great to support the hypothesis of direct proton transfer. A careful analysis of all available crystal structures reveals that the relative positioning of residues Asp-30 and Cys-39 as well as hydrophobic contacts in the vicinity of residue Asp-30 do not allow a conformational change sufficient to bring the two residues close enough for a direct proton transfer. This suggests that protonation/deprotonation of Cys-39 should be mediated by a water molecule. Molecular-dynamics simulations, carried out either in vacuo or in water, as well as proton-inventory experiments, support this hypothesis. The results are discussed with respect to biochemical and structural data.

A mutation in the alpha 1-tubulin gene of Chlamydomonas reinhardtii confers resistance to anti-microtubule herbicides

1993 ◽  
Vol 106 (1) ◽  
pp. 209-218 ◽  
Author(s):  
S.W. James ◽  
C.D. Silflow ◽  
P. Stroom ◽  
P.A. Lefebvre
Keyword(s):  
Chlamydomonas Reinhardtii ◽  
Resistance Mutation ◽  
In Vitro Translation ◽  
Predicted Amino Acid Sequence ◽  
Two Dimensional ◽  
Wild Type ◽  
Tubulin Gene ◽  
Alpha Tubulin ◽  
Tubulin Genes

A mutation in the alpha 1-tubulin gene of Chlamydomonas reinhardtii was isolated by using the amiprophos-methyl-resistant mutation apm1-18 as a background to select new mutants that showed increased resistance to the drug. The upA12 mutation caused twofold resistance to amiprophos-methyl and oryzalin, and twofold hypersensitivity to the microtubule-stabilizing drug taxol, suggesting that the mutation enhanced microtubule stability. The resistance mutation was semi-dominant and mapped to the same interval on linkage group III as the alpha 1-tubulin gene. Two-dimensional gel immunoblots of proteins in the mutant cells revealed two electrophoretically altered alpha-tubulin isoforms, one of which was acetylated and incorporated into microtubules in the axoneme. The mutant isoforms co-segregated with the drug-resistance phenotypes when mutant upA12 was backcrossed to wild-type cells. Two-dimensional gel analysis of in vitro translation products showed that the non-acetylated variant alpha-tubulin was a primary gene product. DNA sequence analysis of the alpha 1-tubulin genes from mutant and wild-type cells revealed a single missense mutation, which predicted a change in codon 24 from tyrosine in wild type to histidine in mutant upA12. This alteration in the predicted amino acid sequence corroborated the approximately +1 basic charge shift observed for the variant alpha-tubulins. The mutant allele of the alpha 1-tubulin gene was designated tua1-1.

scholarly journals The role of LHCBM1 in non-photochemical quenching in Chlamydomonas reinhardtii

2022 ◽  
Author(s):  
Xin Liu ◽  
Wojciech J Nawrocki ◽  
Roberta Croce
Keyword(s):  
Chlamydomonas Reinhardtii ◽  
Protein Complexes ◽  
Ph Sensor ◽  
High Light ◽  
Photochemical Quenching ◽  
Knock Out ◽  
Photosynthetic Organisms ◽  
Pigment Protein Complexes ◽  
Non Photochemical Quenching

Non-photochemical quenching (NPQ) is the process that protects photosynthetic organisms from photodamage by dissipating the energy absorbed in excess as heat. In the model green alga Chlamydomonas reinhardtii, NPQ was abolished in the knock-out mutants of the pigment-protein complexes LHCSR3 and LHCBM1. However, while LHCSR3 was shown to be a pH sensor and switching to a quenched conformation at low pH, the role of LHCBM1 in NPQ has not been elucidated yet. In this work, we combine biochemical and physiological measurements to study short-term high light acclimation of npq5, the mutant lacking LHCBM1. We show that while in low light in the absence of this complex, the antenna size of PSII is smaller than in its presence, this effect is marginal in high light, implying that a reduction of the antenna is not responsible for the low NPQ. We also show that the mutant expresses LHCSR3 at the WT level in high light, indicating that the absence of this complex is also not the reason. Finally, NPQ remains low in the mutant even when the pH is artificially lowered to values that can switch LHCSR3 to the quenched conformation. It is concluded that both LHCSR3 and LHCBM1 need to be present for the induction of NPQ and that LHCBM1 is the interacting partner of LHCSR3. This interaction can either enhance the quenching capacity of LHCSR3 or connect this complex with the PSII supercomplex.

scholarly journals Increased metal tolerance and bioaccumulation of zinc and cadmium in Chlamydomonas reinhardtii expressing a AtHMA4 C-terminal domain protein

2020 ◽  
Author(s):  
Aniefon Ibuot ◽  
Rachel E. Webster ◽  
Lorraine E. Williams ◽  
Jon K. Pittman
Keyword(s):  
Chlamydomonas Reinhardtii ◽  
Metal Binding ◽  
Metal Tolerance ◽  
Alginate Beads ◽  
Full Length ◽  
Wild Type ◽  
Microalgal Biomass ◽  
Terminal Domain ◽  
Metal Biosorption ◽  
Transgenic Cells

AbstractThe use of microalgal biomass for metal pollutant bioremediation might be improved by genetic engineering to modify the selectivity or capacity of metal biosorption. A plant cadmium (Cd) and zinc (Zn) transporter (AtHMA4) was used as a transgene to increase the ability of Chlamydomonas reinhardtii to tolerate 0.2 mM Cd and 0.3 mM Zn exposure. The transgenic cells showed increased accumulation and internalisation of both metals compared to wild type. AtHMA4 was expressed either as the full-length protein or just the C-terminal tail, which is known to have metal binding sites. Similar Cd and Zn tolerance and accumulation was observed with expression of either the full-length protein or C-terminal domain, suggesting that enhanced metal tolerance was mainly due to increased metal binding rather than metal transport. The effectiveness of the transgenic cells was further examined by immobilisation in calcium alginate to generate microalgal beads that could be added to a metal contaminated solution. Immobilisation maintained metal tolerance, while AtHMA4-expressing cells in alginate showed a concentration-dependent increase in metal biosorption that was significantly greater than alginate beads composed of wild type cells. This demonstrates that expressing AtHMA4 full-length or C-terminus has great potential as a strategy for bioremediation using microalgal biomass.

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