Rapid, systemic repression of the synthesis of ribulose 1,5-bisphosphate carboxylase small-subunit mRNA in fungus-infected or elicitor-treated potato leaves.

The levels of ribulose 1,5-bisphosphate carboxylase small-subunit (SSU) mRNA and protein decreased considerably in potato (Solanum tuberosum L.) leaves upon infection with the pathogenic fungus,Phytophthora infestans, or upon treatment with an elicitor preparation from the fungal culture fluid. This effect occurred systemically throughout the affected leaf, regardless of whether the interaction withP. infestans was compatible or incompatible. Using the comparatively drastic and synchronous response to fungal elicitor, we demonstrated that the repression of SSU synthesis was caused by rapid gene inactivation. The timing of repression was similar to that observed previously for the transcriptional activation of various pathogen defense reactions. This supports the hypothesis that induction of the extensive, multi-component defense response requires repression of other cellular functions to ensure metabolic balance.