β -Glucuronidase (GUS) Gene (uidA).
The enzyme -glucuronidase, popularly described as GUS, breaks down glucuronides giving a coloured reaction, so that its presence can be detected in situ, i.e. inside the plant tissue, used either as thin sections or in any other form. Several glucuronides, which can be used as substrates, include p-nitro phenyl glucuronide (PNPG), 5-bromo, 4-chloro, 3-indolyl glucuronide (BCIG), naphthol AS-B 1 glucuronide (NAG) and resorufin glucuronide (REG). The enzyme GUS is coded by a gene uidA,first isolated from E. coli.The major advantage of using this reporter gene (scoreable marker lies in its assay, which requires no DNA extraction, electrophoresis or autoradiography.