Skip to Content
Merck
  • Characterization of singlet oxygen-accumulating mutants isolated in a screen for altered oxidative stress response in Chlamydomonas reinhardtii.

Characterization of singlet oxygen-accumulating mutants isolated in a screen for altered oxidative stress response in Chlamydomonas reinhardtii.

BMC plant biology (2010-12-21)
Beat B Fischer, Rik Il Eggen, Krishna K Niyogi
ABSTRACT

When photosynthetic organisms are exposed to harsh environmental conditions such as high light intensities or cold stress, the production of reactive oxygen species like singlet oxygen is stimulated in the chloroplast. In Chlamydomonas reinhardtii singlet oxygen was shown to act as a specific signal inducing the expression of the nuclear glutathione peroxidase gene GPXH/GPX5 during high light stress, but little is known about the cellular mechanisms involved in this response. To investigate components affecting singlet oxygen signaling in C. reinhardtii, a mutant screen was performed. Mutants with altered GPXH response were isolated from UV-mutagenized cells containing a GPXH-arylsulfatase reporter gene construct. Out of 5500 clones tested, no mutant deficient in GPXH induction was isolated, whereas several clones showed constitutive high GPXH expression under normal light conditions. Many of these GPXH overexpressor (gox) mutants exhibited higher resistance to oxidative stress conditions whereas others were sensitive to high light intensities. Interestingly, most gox mutants produced increased singlet oxygen levels correlating with high GPXH expression. Furthermore, different patterns of altered photoprotective parameters like non-photochemical quenching, carotenoid contents and α-tocopherol levels were detected in the various gox mutants. Screening for mutants with altered GPXH expression resulted in the isolation of many gox mutants with increased singlet oxygen production, showing the relevance of controlling the production of this ROS in photosynthetic organisms. Phenotypic characterization of these gox mutants indicated that the mutations might lead to either stimulated triplet chlorophyll and singlet oxygen formation or reduced detoxification of singlet oxygen in the chloroplast. Furthermore, changes in multiple protection mechanisms might be responsible for high singlet oxygen formation and GPXH expression, which could either result from mutations in multiple loci or in a single gene encoding for a global regulator of cellular photoprotection mechanisms.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Sulfatase from Aerobacter aerogenes, Type VI, buffered aqueous glycerol solution, 2-5 units/mg protein (biuret), 10-20 units/mL
Sigma-Aldrich
Sulfatase from Helix pomatia, Type H-1, sulfatase ≥10,000 units/g solid
Sigma-Aldrich
Sulfatase from abalone entrails, Type VIII, lyophilized powder, 20-40 units/mg solid
Sigma-Aldrich
Sulfatase from Helix pomatia, Type H-2, aqueous solution, ≥2,000 units/mL
Sigma-Aldrich
Sulfatase from Patella vulgata (keyhole limpet), Type IV, essentially salt-free, lyophilized powder, ≥10 units/mg solid