UCLA

Modern agriculture relies heavily on a small selection of widespread market-dominant herbicides, many of which share overlapping modes of action such as ALS inhibition from Chlorsulfuron and EPSP inhibition from Round-Up ready. This widespread use has caused a substantial increase in the number and types of herbicide resistant weeds throughout the world which underlies the near future need for herbicides with novel modes of action. Aspterric acid is a sesquiterpenoid herbicide which inhibits the DHAD enzyme of the branched chain amino acid pathway (BCAA); this enzyme is not targeted by any commercial herbicide on the market which makes aspterric acid an ideal candidate for a novel herbicide. Yarrowia lipolytica, an oleaginous yeast strain, stands out as a promising microbial platform for biosynthetic production of aspterric acid due to its high acetyl-CoA flux and a growing body of literature affirming Y. lipolytica as particularly suited for the over-production of terpenoids. The four ast genes (A,B,C,D) involved in the aspterric acid synthesis pathway were markerlessly integrated into the Y. lipolytica host genome, along with gene copies for HMGCR and FPPS which would overexpress commonly noted rate-limiting enzymes involved in terpenoid synthesis so as to further enhance carbon flux towards terpenoid production. However, the engineered strains of Y. lipolytica failed to produce aspterric acid and instead yielded an isomer, demonstrating the continued challenges that follow from attempts at heterologous pathway introduction into this microbe.