INHIBITION OF PHENOLIC-ACID METABOLISM RESULTS IN PRECOCIOUS CELL-DEATH AND ALTERED CELL MORPHOLOGY IN LEAVES OF TRANSGENIC TOBACCO PLANTS

Several complex phenotypic changes are induced when the transcription factor AmMYB308 is overexpressed in transgenic tobacco plants. We have previously shown that the primary effect of this transcription factor is to inhibit phenolic acid metabolism. In the plants that we produce d, two morphological features were prominent: abnormal leaf palisade d evelopment and induction of premature cell death in mature leaves. Evi dence from the analysis of these transgenic plants suggests that both changes resulted from the lack of phenolic intermediates. These result s emphasize the importance of phenolic secondary metabolites in the no rmal growth and development of tobacco. We suggest that phenolic acid derivatives are important signaling molecules in the final stages of l eaf palisade formation and that phenolic acid derivatives also play a prominent role in tissue senescence.