Inhibition of Phenolic Acid Metabolism Results in Precocious Cell Death and Altered Cell Morphology in Leaves of Transgenic Tobacco Plants

Abstract

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 produced, two morphological features were prominent: abnormal leaf palisade development and induction of premature cell death in mature leaves. Evidence from the analysis of these transgenic plants suggests that both changes resulted from the lack of phenolic intermediates. These results emphasize the importance of phenolic secondary metabolites in the normal growth and development of tobacco. We suggest that phenolic acid derivatives are important signaling molecules in the final stages of leaf palisade formation and that phenolic acid derivatives also play a prominent role in tissue senescence.

A coumaroyl-ester-3-hydroxylase Insertion Mutant Reveals the Existence of Nonredundant meta-Hydroxylation Pathways and Essential Roles for Phenolic Precursors in Cell Expansion and Plant Growth

“…Phenolic compounds have been reported to play a role in cell division and expansion, either directly or as components of a cytokinin-dependent signaling cascade . A major role in this respect was attributed to dehydrodiconiferyl alcohol glucoside (DCG), which was shown to directly activate cell growth and division in tobacco (Nicotiana tabacum) pith, leaves, or cell cultures (Binns et al, 1987;Tamagnone et al, 1998). DCG, as lignin G monomers, is expected to directly derive from CYP98A3 products (Fig.…”

“…The pathways inactivated are shown in gray. The monolignol DCG has been described as a growth regulator (Binns et al, 1987;Tamagnone et al, 1998). Aromatic amino acids, including Phe, are synthesized in the plastids via the so-called shikimate pathway (Herrmann and Weaver, 1999).…”

Transcript-Based Cloning ofRRP46, a Regulator of rRNA Processing andRGene–Independent Cell Death in Barley–Powdery Mildew Interactions

“…In plants, cell death is often correlated with development and metabolism and their associated differentiation, reproduction, and vegetative growth (Beers, 1997;Tamagnone et al, 1998). RNA processing represents an essential metabolic pathway throughout these stages.…”

Novel Hydroxycinnamoyl-Coenzyme A Quinate Transferase Genes from Artichoke Are Involved in the Synthesis of Chlorogenic Acid

“…tomato [Solanum lycopersicum], tobacco [Nicotiana tabacum], and eggplant [Solanum melongena]), apple (Malus domestica), pear (Pyrus communis), plum (Prunus domestica), coffee (Coffea arabica), and artichoke (Tamagnone et al, 1998a;Clifford, 1999;Wang et al, 2003;Schü tz et al, 2004) and is believed to play important roles in free radical scavenging (Chen and Ho, 1997;Tamagnone et al, 1998b), enzymatic browning of fruits and vegetables (Walker, 1995), defense against fungal pathogens (Maher et al, 1994), and resistance to pathogenic insects (Dowd and Vega, 1996;Bushman et al, 2002). The biosynthetic routes leading to CGA in plants are not completely defined yet, and three possible paths have been proposed.…”