OZONE-INDUCED ETHYLENE EMISSION ACCELERATES THE LOSS OF RIBULOSE-1,5-BISPHOSPHATE CARBOXYLASE OXYGENASE AND NUCLEAR-ENCODED MESSENGER-RNAS IN SENESCING POTATO LEAVES

The relationships among O-3-induced accelerated senescence, induction of ethylene, and changes in specific mRNA and protein levels were investigated in potato (Solanum toberosum L. cv Norland) plants. When plants were exposed to 0.08 mu L L(-1) O-3 for 5 h d(-)1, steady-state levels of rbcS mRNA declined at least 5-fold in expanding leaves after 3 d of O-3 exposure and ethylene levels increased 6- to 10-fold. The expression of OIP-1, a 1-aminocyclopropane-1-carboxylate synthase cDNA from potato, correlated with increased production of ethylene and decreased levels of rbs mRNA in foliage of plants treated with O-3. In plants exposed to 0.30 mu L L(-1) O-3 for 4 h, rbcS transcript levels were reduced 4-fold, whereas nuclear run-on experiments revealed that rbcS transcription declined an average of 50%. The loss of rbcS mRNA may be due, in part, to posttranscriptional regulation. The levels of transcripts for other chloroplast proteins, glyceraldehyde-3-phosphate dehydrogenase, and a photosystem II chlorophyll a/b-binding protein decreased in O-3-treated plants, in parallel with the decrease in rbcS mRNA. The steady-state mRNA level of a cytosolic glyceraldehyde-3-phosphate dehydrogenase increased in O-3-treated plants. The induction of ethylene and changes in transcript levels preceded visible leaf damage and decreases in ribulose-1,5-bisphosphate carboxylase/oxygenase protein levels.