AMP deaminase suppression increases biomass, cold tolerance and oil content in green algae

Abstract

The green algae, Chlamydomonas reinhardtii, is currently one of the most targeted organisms for renewable biofuel production, yet its growth depends strictly on warm (subtropical) conditions. This requirement makes C. reinhardtii not only susceptible to cold stress, but also unsuitable for culturing large scale algae year round in temperate regions. Using RNAi mediated gene knockdown, we targeted the AMP degradation enzyme, AMP deaminase (AMPD), to reflect psychrophilic-like purine metabolism (purine metabolism in cold adapted organisms) in C. reinhardtii. The engineered C. reinhardtii strains elevated intracellular steady-state ATP levels by more than twofold across their viable temperature range, displayed ~3-fold higher growth rate and biomass, and ~25% higher lipid/oil accumulation compared to wild-type under both normal and cold growth conditions. Our findings can be extrapolated to engineer plants that grow under cold stress conditions for sustainable agriculture and plant-based biofuel production.