Identification of the mutation responsible for negative phototaxis in a "wild-type" strain of .

The unicellular green alga is a model organism for various studies in biology. CC-124 is a laboratory strain widely used as a wild type. However, this strain is known to carry mutation, which causes cells to swim away from the light source (negative phototaxis), in contrast to the cells of other wild-type strains, which swim toward the light source (positive phototaxis).

Eyespot-dependent determination of the phototactic sign in Chlamydomonas reinhardtii.

The biflagellate green alga Chlamydomonas reinhardtii exhibits both positive and negative phototaxis to inhabit areas with proper light conditions. It has been shown that treatment of cells with reactive oxygen species (ROS) reagents biases the phototactic sign to positive, whereas that with ROS scavengers biases it to negative. Taking advantage of this property, we isolated a mutant, lts1-211, which displays a reduction-oxidation (redox) dependent phototactic sign opposite to that of the wild type.

Redox regulation of phototactic migration in the green alga Chlamydomonas reinhardtii and its possible application.

Most flagellated green algae swim toward or away from the light source, i.e., display positive or negative phototaxis.

Reduction-oxidation poise regulates the sign of phototaxis in Chlamydomonas reinhardtii.

In many phototrophic microorganisms and plants, chloroplasts change their positions relative to the incident light to achieve optimal photosynthesis. In the case of motile green algae, cells change their swimming direction by switching between positive and negative phototaxis, i.e.