Expression of a gene at high levels results in production of large quantities of its protein product. This can be useful for production of some important protein on an industrial scale, or for the physiological effects of overexpression.

Overexpression of phytochrome in tomatoes

Phytochrome is an intracellular protein which governs processes in the plant that are switched on or off by light.
Undisplayed Graphic

Tomato plants overexpressing oat phytochrome (right) are dwarfed, but set fruit earlier than untransformed plants (left). Fruit from transformed plants had a normal color and size.

The USDA-ARS Plant Genome Research Program. USDA Program Aid 1500. March 1994.
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