Metabolic Engineering for Production of Lipids in Vegetative Sugarcane Biomass

Metabolic engineering to divert carbon flux from sucrose to oil in a high biomass crop like sugarcane has been proposed as a strategy to boost lipid yields per acre for biodiesel production. The energy content of plant oils in the form of triacylglycerols (TAGs) is two-fold greater compared to carbohydrates. However, vegetative plant tissues do not accumulate oil to a significant amount since fatty acid synthesis in these tissues serves primarily membrane construction, in addition TAGs undergo rapid turnover. Therefore, our objectives include:

1.) increasing fatty acid synthesis by expressing a transcription activator of fatty acid biosynthetic genes,

2.) increasing fatty acid synthesis by suppressing lipid re-import into the plastids from the cytoplasm,

3.) increasing TAG synthesis from diacyl-glycerol and acyl-CoA by over-expression of rate limiting enzymes,

4.) optimizing TAG storage by limiting the access of lipases to TAG storage compartments.

Constitutive single or multiple gene expression/suppression cassettes were generated and co-delivered with the selectable nptII expression cassette by biolistic gene transfer into sugarcane. Plants were regenerated on geneticin containing culture medium and analyzed for presence and expression of target constructs by PCR and RT-PCR, respectively. Plants were analyzed for TAG content by Gas-Chromatography and Mass Spectrometry (GC-MS).

The presented research outcome will add value to sugarcane for production of advanced biofuels.