Photosynthesis & Glycogen Metabolism

Cyanobacteria drastically change their carbon metabolism under daily light-dark cycles. Carbon fixed during the day is partially stored as glycogen to support cellular respiration in the dark. Cellular respiration contributes largely to the survival of cyanobacteria in the dark, and the smooth dark-to-light transition. Recent studies in the field highlighted the genetic background important for the fitness of cyanobacterial during diurnal growth. Expanding from these research, we found that the cyanobacterium Synechococcus elongatus can leverage cellular respiration to support photosynthesis during dark-light transition. It is likely that this strategy has empowered cyanobacteria and green plants with evolutionary advantages to stabilize photosynthetic reactions. We are working to dissect the metabolic engagement during dark-to-light transition in cyanobacteria.

Photosynthetic Terpene Biofuels

Terpenes are the largest family of secondary metabolites produced by plants, and have diverse industrial applications. Terpene molecules are generated from two C5 precursor molecules, IPP and DMAPP. In cyanobacteria, the MEP pathway condenses two glycolysis intermediates, glyceraldehyde 3-phosphate (G3P) and pyruvate into IPP/DMAPP. Cells also invest large amount of energy and reducing equivalents to form the high-energy diphosphate bond in IPP/DMAPP and to saturate the carbon chain. 

Currently, metabolic regulation to the MEP pathway is largely unknown, which posts as a major challenge for the study of the MEP pathway and to metabolic engineering efforts. Our research expands from an engineered Synechococcus elongatus strain that can produce limonene at high titer. Through various omics (transcriptomics, proteomics, metabolomics, and fluxomics) approaches, we intend to better understand the carbon flux distribution between terpene and central metabolism. The ultimate goal is to dissect cell regulation on carbon flux distribution among various metabolic processes, and infer genetic perturbation to alter carbon flux for practical applications.