Regulation and function of photo-oxidative stress induced crGPX5/GPXH in Chlamydomonas reinhardtii

Rik I.L. Eggen1, Régine Dayer1 and Beat B Fischer2

1Eawag, Swiss Federal Institute of Aquatic Science and Technology, Dübendorf, Switzerland 2 Department of Plant and Microbial Biology, University of California, Berkeley, USA.

Photosynthetic organisms are confronted with reactive oxygen species (ROS) such as superoxide, hydrogen peroxide, hydroxyl radicals and singlet oxygen. These ROS are produced during normal cell metabolism and are increasingly produced upon photo-oxidatives stress caused by harsh environmental conditions such as high light, drought or exposure to pollutants. ROS can damage biomolecules and cause death. As all aerobic organisms, Chlamydomonas reinhardtii has developed efficient defense mechanisms against ROS by preventing ROS formation, removing them or repairing damaged biomolecules. Among the various enzymatic defense systems, we have examined the expression and function of crGPX5/GPXH in detail. Transcription of the crGPX5 gene is strongly activated by singlet oxygen. Due to mRNA stabilization, levels of crGPX5 mRNA slowly but continuously increase upon exposure to organic hydroperoxides. Details on both regulatory mechanisms and its physiological function in the context of photo-oxidative stress conditions will be discussed. Further research was aimed at identifying the localization and enzymatic activity of the crGPX5/GPXH protein. Our newest results will be presented and discussed during the conference.

e-mail address of presenting author: eggen@eawag.ch