Production of the storage lipid triacylglycerol in vegetative plant tissues
has emerged as a promising strategy to meet the world's need for vegetable
oil. Sorghum (Sorghum bicolor) is an attractive target crop due to its high
biomass, drought resistance and C4 photosynthesis. While oilseed-like
triacylglycerol levels have been engineered in the C3 model plant tobacco,
progress in C4 monocot crops has been relatively slow. This prompted
researchers from CSIRO Agriculture and Food in Australia to modify sorghum
so its leaf tissues produce and accumulate triacylglycerol.
The team overexpressed the maize (Zea mays) WRI1 transcription factor gene,
the UrDGAT2a acyltransferase gene from the fungus Umbelopsis ramanniana and
Oleosin$B!>(BL oil body protein from sesame (Sesamum indicum). Overexpressing
these three genes led to the upregulation of lipid synthesis in the
transgenic sorghum. The resulting transgenics exhibited increased oil
content, which was visible as lipid droplets in the leaf mesophyll cells.
These results present the first step forward towards the development of
sorghum as a biomass oil crop.