The trehalose metabolism in different stress responses of chlamydomonas reinhardtii

Dissaccharide trehalose ( α -D-glycopyranosy1-1,1- α -D-glucopyranoside) is present in many organisms ranging from bacteria to vertebrates. In yeast, trehalose serves not only as energy source but also serves as stress protectant in a variety of stresses including cold, heat, dehydration and oxidation. We use unicellular green flagellates C. reinhardtii, which is highly adaptable to various environments, to study the trehalose metabolism. It involves 2 synthetic enzymes (trehalose-6-phospate synthase, TPS, and trehalose-6-phosphate phosphatase, TPP) and 1 hydrolytic enzyme (trehalase, Treh). In our study, we detected one putative TPS, TPP and Treh gene in C. reinhardtii genome by bioinformatic searching. Their transcriptions were illustrated by RT-PCR. Treh transcription was down regulated immediately in the early stage of cold, heat, NaC1, sorbitol and H2O2 treatment. Therefore, trehalose was predicted to accumulate in algal cells adapting those treatments. Trehalose did not respond in UV, paraquat, Cu, Hg, Pb and Cd treatment. In the detailed study of H2O2 treatment causing 50% growth retardation, we detected the decrease of trehalase activity and the increase of trehalose content. This result is consistent with the protective role of trehalose in C. reinhardtii cells subjected to H2O2 stress