Accumulation of triacylglycerol in green algae

Sulfoquinovosyl diacylglycerol is one of lipids that construct chloroplast membranes. We recently reported that a green alga, Chlamydomonas reinhardtii, when starved for sulfur (S), degrades sulfoquinovosyl diacylglycerol to ensure an intracellular S-source for protein synthesis [1]. In the course of this study, it was newly found that green algae accumulate triacylglycerol (TG) under S-starved conditions. C. reinhardtii contained TG and free fatty acids as neutral lipids at minor amounts under normal growth conditions, then increasing the TG content specifically 24-96 h after onset of S-starvation. A similarly specific increase in the TG content was observed also with another green alga, Chlorella kesslerli 11h. In contrast, neither TG nor free fatty acids accumulated in C. reinhardtii when starved for phosphorus. These results indicated that accumulation of TG is a response that is not general to nutrition-deficient stresses, but specific to S-starvation at least. Green algae are known to accumulate TG under nitrogen-starved conditions. Accumulation of TG may be related to a decrease in protein synthesis.<br>[1] K. Sugimoto, M. Tsuzuki and N. Sato: New Phytol. 185, 676 (2010).