CSIRO Agriculture and Food, Clunies Ross St, Acton 2601, ACT, Australia
Demand for vegetable oil is projected to double world-wide within the next decades due to increasing food, feed, fuel and industrial requirements. Accumulation of excess photosynthetic energy in the form of leaf oil could be a solution to this growing demand. However, lipid (TAG) accumulation tends to be limited in leaves in favour of starch production. The aim of this study was to investigate the relationship between lipid, starch and soluble sugar accumulation in our unique high oil transgenic tobacco plants. In tobacco leaves, oil accumulation was correlated with greatly altered starch and soluble sugar content, although the relationship between carbohydrates and oil was highly dependent on plant and leaf developmental stage. Despite these dramatic shifts in carbon partitioning, high oil plants showed a relatively small reduction in final biomass. Evidence of diurnal cycles of TAG synthesis and degradation suggests that tobacco may be able to take advantage of this novel energy store to fuel growth at night. Further work is being undertaken to determine whether this and other mechanisms may allow tobacco to grow and accumulate oil even with such major changes to primary metabolism. In the long term, the aim of this project is to apply all knowledge gained to further increase agricultural lipid (TAG) productivity and to generate novel products for food and industry.