Investigating a novel role of LARP along the algal TOR pathway

Abstract

Over the last few decades, global warming has become an increasingly desperate rallying cry for the need to find and optimize efficient renewable energy sources.1 Microalgae are considered apromising source of energy because they contain a high concentration of lipids, but due to inefficiencies in their lipid production, microalgae cannot produce enough biofuel to replace current fuel needs.2Chlamydomonas reinhardtiiis a unicellular green alga that is a great candidate for manipulation and an excellent model organism used to better understand algal metabolic pathways and improve biofuels. Our previous research has shown that inhibiting the target of rapamycin (TOR) kinase of C. reinhardtii with AZD8055 causes the growth of the cell cultures to stagnate, the photosynthetic efficiency to decrease, as well as a direct link between oxidative signaling and the upregulation of TAGs.3 Additionally, our work has indicated that La‐related protein 1 (LARP1) is a TOR target and involved in propagating the intracellular response following inhibition. In mammalian systems, LARP1 interacts directly with mTOR and regulates protein synthesis by binding and stabilizing mRNA before recruiting polysomes to initiate translation. LARP1 is essential in mammalian systems, and deficiencies lead to inhibited growth, defects, and increased apoptosis. However, LARP1 deficiency in C. reinhardtii does not cause the same phenotype, indicating a distinct uncharacterized role in phototrophic organisms.This study seeks to understand this role by using a LARP1 knockout mutant to compare the physiological changes following inhibition with the parent strain. Both strains were assessed for biochemical composition, cell size, and photosynthetic electron fluxes. Together, these data support LARP1 as a regulator of protein degradation along the TOR pathway. The differential delineation of metabolic processes in LARP1 knockouts provides a framework for further TOR pathway characterization in phototrophic eukaryotes.Literature References1 IPCC, 2014: Climate Change 2014: Synthesis Report. Contribution of Working Groups I, II and III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Core Writing Team, R.K. Pachauri and L.A. Meyer (eds.)]. IPCC, Geneva, Switzerland, 151 pp.2 Sharma, Kalpesh K., Holger Schuhmann, and Peer M. Schenk.. High Lipid Induction in Microalgae for Biodiesel Production. 2012. Energies. 5:1532‐1553.3 Ford, M. M., Smythers, A. L., McConnell, E. W., Lowery, S. C., Kolling, D. R. J., & Hicks, L. M. (2019). Inhibition of TOR in Chlamydomonas reinhardtii leads to rapid cysteine oxidation reflecting sustained physiological changes. Cells, 8(10), 1171.