ADP-RIBOSYLATION FACTOR (ARF) REGULATES CAMP SYNTHESIS IN POTATO

Transgenic potato plants expressing a reduced level of ADP-ribosylatio n factor (ARF) were created using the antisense RNA technique. The tra nsformants show slight differences in the process of tuber formation. The reduction of stolons and appearance of knobby tubers is a characte ristic feature of these potato plants. A significant increase in cAMP content in the leaves of transgenic plants has been detected. A parall el increase in the phosphorylation stare of a 60 kD protein is, howeve r, not the consequence of cAMP enhancement. It is demonstrated that wi ld type and transgenic potato plants contain two ARF fractions differi ng in extractability by Triton X-100. The very young (i.e. sink) leave s contain mostly a fraction that can be released by a high concentrati on of Triton X-100 (at least 1%); mature (i.e. source) leaves appear t o have an easily extractable ARF fraction (0.1% Triton X-100) protein. The decrease in the ARF content in transgenic potato lines results in accumulation of the 14-3-3 protein (27 kD isoform). It is postulated that most biochemical changes that appeared in ARF-antisense potato pl ants resulted from an increase in cAMP content in transgenic plants.