Arogenate Dehydratase Isoenzymes Profoundly and Differentially Modulate Carbon Flux into Lignins

Abstract

Background:The plastid-localized arogenate dehydratase (ADT) gene family is hypothesized to differentially control carbon flux for lignin deposition, with lignin being the main contributor to lignocellulosic recalcitrance. Results: Single and multiple ADT knock-outs resulted in differential control over lignin content/composition. Conclusion: The first evidence for Phe upstream metabolism differentially controlling carbon flux into distinct secondary cell wall types was discovered. Significance: Upstream metabolic networks regulate secondary cell wall formation.

Subcellular localization of Arabidopsis arogenate dehydratases suggests novel and non-enzymatic roles

“…Interestingly, no T-DNA insertion knockout lines that abolish ADT2 mRNA are available (Corea et al , 2012 b ). This makes ADT2 unique and raises the possibility that an adt2 knockout is lethal.…”

A Key Role for Apoplastic H2O2 in Norway Spruce Phenolic Metabolism

“…7; Supplemental Table S6). Certain isoenzymes of arogenate dehydratase have been shown to profoundly and differentially modulate carbon flux into the downstream lignin biosynthesis pathway in Arabidopsis (Corea et al, 2012a(Corea et al, , 2012b. It seems likely that the induced genes in spruce encode isoenzymes responsible for the synthesis of Phe destined for monolignol and/or flavonoid biosynthesis, while some other isoenzymes are responsible for the formation of Phe utilized for protein synthesis.…”

Phylobiochemical Characterization of Class-Ib Aspartate/Prephenate Aminotransferases Reveals Evolution of the Plant Arogenate Phenylalanine Pathway

“…The eukaryotic host of the plant ancestor, or the free-living cyanobacterium that gave rise to the primary plastid, acquired both PPA-AT and ADT from an ancestor of Chlorobi/Bacteroidetes bacteria. The introduction of the PPA-AT and ADT enzymes allowed plants to synthesize Phe predominantly via the arogenate pathway (Jung et al, 1986;Maeda et al, 2010;Yoo et al, 2013), which currently supports the production of diverse and abundant phenylpropanoid natural products, including lignin (Corea et al, 2012b).…”

“…Biochemical characterization of recombinant plant ADT enzymes showed that they have substrate preference toward arogenate over prephenate (Cho et al, 2007;Yamada et al, 2008;Maeda et al, 2010). Genetic analysis of plant ADTs further demonstrated that Phe is predominantly synthesized via the arogenate in plants (Maeda et al, 2010;Corea et al, 2012aCorea et al, , 2012b. However, phylogenetic analyses showed that the arogenate and prephenate specificity of ADH/PDH and ADT/PDT do not map tidily onto a single clade of the gene tree, suggesting that their substrate specificity has been gained and/or lost multiple times in the gene family's evolution (Jensen, 1985;Song et al, 2005).…”

“…Unlike the major effect of ADT suppression on the levels of Phe and Phe-derived compounds (Maeda et al, 2010, Corea et al, 2012a, 2012b, PPA-AT suppression led to a minor reduction in Phe levels (Maeda et al, 2011;de la Torre et al, 2014). However, this was due to compensatory operation of Phe biosynthesis via alternative phenylpyruvate pathway mediated by a separate phenylpyruvate aminotransferase (Yoo et al, 2013), which is homologous to tyrosine aminotransferase and has a broad substrate specificity (Gelfand and Steinberg, 1977;Gonda et al, 2010;Lee and Facchini, 2011;Riewe et al, 2012).…”