CAREER: Uncoupling Growth and Triacylglycerol Accumulation in Algae

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Photosynthetic microalgae show great promise for meeting US demands for renewable, sustainable, and affordable biofuels. Algae are dynamic living systems wherein external and internal signals are integrated to produce metabolic changes over time that can promote the accumulation of lipids, a component of biodiesel fuels. This CAREER project will determine how internal signals regulate the flow of carbon from basic functions like cell growth to alternative pathways such as production of lipids. The focus of this project is on the TARGET of RAPAMYCIN signaling network that has been characterized extensively in animals and fungi, but is much less understood in photosynthetic organisms. This information will provide insights into whether this signaling network can be harnessed and/or bypassed to improve lipid production. A diverse population of graduate, undergraduate and high-school students will be trained in mass spectrometry, proteomics, molecular biology, analytical chemistry and bioinformatics as part of the research and tightly aligned research-oriented educational aims of this project.Understanding the regulatory processes governing energy-dense compound production is essential for controlling carbon capture, partitioning, and storage in photosynthetic microalgae. In this work, the TARGET of RAPAMYCIN (TOR) signaling pathway in Chlamydomonas will be elucidated in order to facilitate strategies to decouple cellular growth from triacylglycerol accumulation. The TOR kinase pathway is a conserved eukaryotic regulator of growth in response to stress, nutrients and energy supply. There is only a nascent understanding of its role in photosynthetic organisms. There is not yet a comprehensive understanding of the pathway, its coordination, or of the interplay between nutrient deprivation and kinase-mediated signal transduction. This project will employ an integrative strategy of genetics, molecular biology, and mass spectrometry to i) identify direct and indirect substrates of TOR kinase activity in vivo, ii) establish TOR protein network connectivity through delineation of substrates and effectors, and iii) develop a research-inspired mass spectrometry curriculum for undergraduate/graduate education. This systems-level description of TOR signaling will provide insight into how the TOR pathway can be harnessed and/or bypassed in order to uncouple the process of cell growth from triacylglycerol accumulation.