TOR kinase activity in Chlamydomonas  reinhardtii is modulated by cellular metabolic states

Target of rapamycin (TOR) kinase is a sensor and a central integrator of internal and external metabolic cues. However, in algae and in higher plants, the components of TOR kinase signaling are yet to be characterized. Here, we establish an assay system to study TOR kinase activity inChlamydomonas  reinhardtii using the phosphorylation status of its putative downstream target, CrS6K. Using this assay, we probe the modulation of cellular TOR kinase activity under various physiological states such as photoautotrophy, heterotrophy, mixotrophy, and nitrogen (N) starvation. Importantly, we uncover that excess acetate in the medium leads to high cellular reactive oxygen species levels, triggering autophagy and a concomitant drop in TOR kinase activity in a dose ‐dependent manner, thus leading to a N‐starvation‐like cellular phenotype, even when nitrogen is present.

Source: FEBS Letters - August 2, 2020 Category: Biochemistry Authors: Shivani Upadhyaya, Shreya Agrawal, Anmol Gorakshakar, Basuthkar Jagadeeshwar Rao Tags: Research Article Source Type: research