Chlamydomonas urium Genome sequencing. Chlamydomonas urium strain:IBVF

The genome of Chlamydomonas urium was sequenced, assembled and annotated to identify autophagy-related genes. Furthermore, transmission electron microscopy, immunoblotting, metabolomic and photosynthetic analyses were performed to study autophagy in this extremophilic microalga. Conservation of core autophagy-related genes was revealed by analysis of the Chlamydomonas urium genome. We investigated the role of autophagy in Chlamydomonas urium by blocking autophagic flux using the vacuolar ATPase inhibitor concanamycin A. Our results showed that inhibiting autophagic flux in this microalgae resulted in massive accumulation of triacylglycerols and lipid droplets. Metabolomic and photosynthetic analyses indicated that Chlamydomonas urium cells with impaired vacuolar function maintained an active central metabolism. In the neutrophilic model green alga Chlamydomonas reinhardtii, no such effects were observed. Inhibition of autophagic flux in Chlamydomonas urium revealed active recycling of lipid droplets by lipophagy, a selective autophagic pathway for lipid turnover. This study provided the metabolic basis by which extremophilic algae can catabolize vacuolar lipids.