β Glucuronidase GUS Gene - The enzyme β-glucuronidase, popularly described as GUS, breaks down glucuronidase giving a coloured reaction, so that its presence can be detected in situ, i.e. inside the plant tissue, used either as thin section or in any other form.

Several glucuronidase, which can be used as substrates, include p-nitro phenyl glucuronide (PNPG), 5-bromo, 4-chloro, 3-indolyl / glucuronide (BCIG), naphthol AS-B1 glucuronide (NAG) and resorufin glucuronide (REG).

The enzyme GUS is coded by a gene gus, first isolated from E. coli. The major advantage of using this reporter gene (scoreable marker) lies in its assay, which requires no DNA extraction, electrophonesis or autoradiography