Plants naturally make these compounds for protection. Engineering the system so the cells produce marketable amounts is not. We are trying to identify the rate limiting step. What the researchers have found is that the levels of secondary metabolite in the growth media regulate its production rate. When the level does drop, enzymes in the cell can rapidly produce more.
Plants produce secondary metabolites as a defensive measure.
These chemicals defend against attach by microbes with antibiotics, fungi with antifungals, predators with pesticides and other plants with herbicides. The researchers are currently looking at production of sesquiterpenes, antifungal agents produced by plants in the potato, tomato and tobacco family. Because of their food value and susceptibility to disease, the molecular biology and biochemistry of these crops is better known than most plants. In biological systems, it's more complicated and there is a whole series of steps, any one of which can limit production. The plant, logically, identifies a piece of fungus or other elicitor as an indication that the entire, active enemy will follow shortly.