Manipulation of Metabolic Partitioning

The flow of metabolites through metabolic and biosynthetic pathways is regulated to respond to developmental and environmental conditions.
The distribution of metabolites (partitioning) controls the flux of carbon compounds towards the synthesis of sugars, starch and oils in storage organs and may change to meet developmental states, environmental constraints or in the activation of the diverse array of defence responses when a plant is attacked by pathogens. Metabolic fluxes can be manipulated and an understanding of the control of partitioning between metabolic pathways is required for metabolic engineering – this knowledge can be used to increase the production or yield of commercially important metabolites and products. Strategies to modify partitioning include:
(i) changing levels of signalling metabolites and hormones;
(ii) removal of end products to change reaction equilibria;
(iii) expression of heterologous enzymes to bypass endogenous regulatory mechanisms;
(iv) expression of transcriptional regulators that control pathways;
(v) switching off gene expression by sense/antisense suppression.

Most commercial applications of metabolic partitioning involve altered starch and oil biosynthesis, reducing lignin content or synthesis of biodegradable plastic (polyhydroxybutyrate, PHB), but this aspect is also relevant to all uses of plants as bioreactors to produce more of current or novel compounds efficiently.