The mammalian-type thioredoxin reductase 1 confers a high-light tolerance to the green alga Chlamydomonas reinhardtii

Reactive oxygen species (ROS) can both act as a poison causing cell death and important signaling molecules among various organisms. Photosynthetic organisms inevitably produce ROS, making the appropriate elimination of ROS an essential strategy for survival. Interestingly, the unicellular green alga Chlamydomonas reinhardtii expresses a mammalian form of thioredoxin reductase, TR1, which functions as a ROS scavenger in animal cells. To investigate the properties of TR1 in C. reinhardtii, we generated TR1 knockout strains using CRISPR/Cas9-based genome editing. We found a reduced tolerance to high-light and ROS stresses in the TR1 knockout strains compared to the parental strain. In addition, the regulation of phototactic orientation, known to be regulated by ROS, was affected in the knockout strains. These results suggest that TR1 contributes to a ROS-scavenging pathway in C. reinhardtii. •The mammalian-type thioredoxin reductase 1 (TR1) was knocked out in Chlamydomonas.•The knockout (Δ)TR1 strains displayed a reduced tolerance to high-light stress.•The ΔTR1 strains showed positive phototaxis with low-concentration H2O2 treatment.•TR1 is suggested to scavenge reactive oxygen species in Chlamydomonas cytoplasm.