Silencing of Hydroxycinnamoyl-Coenzyme A Shikimate/Quinate Hydroxycinnamoyltransferase Affects Phenylpropanoid Biosynthesis[W]

Abstract

The hydroxyl group in the 3-position of the phenylpropanoid compounds is introduced at the level of coumarate shikimate/ quinate esters, whose synthesis implicates an acyltransferase activity. Specific antibodies raised against the recombinant tobacco (Nicotiana tabacum) acyltransferase revealed the accumulation of the enzyme in stem vascular tissues of tobacco, in accordance with a putative role in lignification. For functional analysis, the acyltransferase gene was silenced in Arabidopsis thaliana and N. benthamiana by RNA-mediated posttranscriptional gene silencing. In Arabidopsis, gene silencing resulted in a dwarf phenotype and changes in lignin composition as indicated by histochemical staining. An indepth study of silenced N. benthamiana plants by immunological, histochemical, and chemical methods revealed the impact of acyltransferase silencing on soluble phenylpropanoids and lignin content and composition. In particular, a decrease in syringyl units and an increase in p-hydroxyphenyl units were recorded. Enzyme immunolocalization by confocal microscopy showed a correlation between enzyme accumulation levels and lignin composition in vascular cells. These results demonstrate the function of the acyltransferase in phenylpropanoid biosynthesis.

Maize Homologs of CCoAOMT and HCT, Two Key Enzymes in Lignin Biosynthesis, Form Complexes with the NLR Rp1 Protein to Modulate the Defense Response

“…Knocking down the expression of HCT in both Arabidopsis and alfalfa (Medicago sativa) leads to a dwarf phenotype, with constitutive activation of defense responses, including increased PR gene expression and elevated SA levels (Hoffmann et al, 2004;Li et al, 2010;Gallego-Giraldo et al, 2011a, 2011b. HCT-down-regulated alfalfa also enhances disease resistance to the fungus Colletotrichum trifolii, the causal agent of alfalfa anthracnose (GallegoGiraldo et al, 2011b).…”

“…The phenylpropanoid pathway, adapted from previous studies (Hoffmann et al, 2004;Li et al, 2010;Wang et al, 2015c).…”

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

“…Similar substrate specificity may have evolved independently in different species for some BAHD acyltransferases; therefore, experimental validation tests are needed to definitively identify acyltransferase function (D'Auria, 2006;Luo et al, 2007). Enzymes with HQT activity and showing a preference for quinate over shikimate as acyl acceptor cluster together in phylogenetic trees and are clearly distinct from HCT enzymes, which generally prefer shikimate to quinate as an acyl acceptor and are thought to work principally in lignin biosynthesis (Hoffmann et al, 2003(Hoffmann et al, , 2004Sullivan, 2009). This clear conservation of catalytic specificity within phylogenetically distinct clades of the BAHD family is surprising given that not all plant species accumulate caffeoylquinate; it might have been predicted that HQT activity would have evolved de novo in species that develop the ability to synthesize CGA, as reported for acylation of anthocyanins (Suzuki et al, 2004).…”

Identification of an Arabidopsis Feruloyl-Coenzyme A Transferase Required for Suberin Synthesis

“…Apart from its demonstrated activity as a feruloyl transferase to an aliphatic acyl acceptor, analysis of the genetic relationships in the BAHD gene family shows it is not closely related to the hydroxycinnamoyl transferase(s) that are implicated in monolignol biosynthesis (Supplemental Fig. S1; Hoffmann et al, 2003Hoffmann et al, , 2004. Cell wall ferulate appears to share a common biosynthetic pathway with monolignols .…”