Induction of the maize GapC4 promoter in transgenic potato under anaerobiosis and in Erwinia carotovora-inoculated tuber tissue

The induction pattern of the GapC4 promoter from maize in transgenic potato has been analyzed by fusion to the beta-glucuronidase (gus) gene. Under an aerobic conditions this promoter confers high level expression not only in leaves, stems, and roots but also in tubers. After inoculation of potato tu ber disks with Erwinia carotovora subsp, atroseptica, beta-glucuronidase (G US) activity could be detected in macerated tissue as well as in surroundin g intact tissue. In mock controls no induction was detected, ruling out any induction due to an overall limitation in oxygen in the experimental syste m. In addition, it could be proven that no diffusion of GUS protein from ma cerated into intact tissue occurred. The promoter was shown to be aerobical ly induced even in the absence of live bacteria by incubation with purified Erwinia spp, pectolytic enzymes alone, Therefore, promoter induction seems to be mediated by a mobile factor instead of by limitation in oxygen. Thes e results demonstrate that the maize GapC4 promoter is suitable for directi ng foreign genes encoding antibacterial proteins in transgenic potato.