Modification of plant cell walls with hydroxycinnamic acids by BAHD acyltransferases

Abstract

In the last decade it has become clear that enzymes in the “BAHD” family of acyl-CoA transferases play important roles in the addition of phenolic acids to form ester-linked moieties on cell wall polymers. We focus here on the addition of two such phenolics—the hydroxycinnamates, ferulate and p-coumarate—to two cell wall polymers, glucuronoarabinoxylan and to lignin. The resulting ester-linked feruloyl and p-coumaroyl moities are key features of the cell walls of grasses and other commelinid monocots. The capacity of ferulate to participate in radical oxidative coupling means that its addition to glucuronoarabinoxylan or to lignin has profound implications for the properties of the cell wall – allowing respectively oxidative crosslinking to glucuronoarabinoxylan chains or introducing ester bonds into lignin polymers. A subclade of ~10 BAHD genes in grasses is now known to (1) contain genes strongly implicated in addition of p-coumarate or ferulate to glucuronoarabinoxylan (2) encode enzymes that add p-coumarate or ferulate to lignin precursors. Here, we review the evidence for functions of these genes and the biotechnological applications of manipulating them, discuss our understanding of mechanisms involved, and highlight outstanding questions for future research.

Altered cell wall hydroxycinnamate composition impacts leaf and canopy-level CO2-uptake and water-use in rice

“…Hydroxycinnamates on arabinoxylan are another unique component of CWs of grasses and other recently evolved monocots, modification of which affects biomass properties Chandrakanth et al, 2023). Our data suggests that overexpression of OsAT10, which results in lower CW FA and greater p-CA content, leads to thinner CWs in the transgenics compared to WT plants.…”

“…Overall, we observed similar compositional, physiological, and anatomical changes in Ubi pro -AT10 transgenics compared to the activation tagged OsAT10-D1 (OsAT10-Dominant 1) . Grass Ubi promoters generally have strong foliar expression, whereas the native AT10 gene has low expression in leaves compared to other related BAHDs (Chandrakanth et al, 2023). Thus, we focused on the Ubi pro -AT10 lines and measured a larger battery of traits, whereas, for OsAT10-D1 only important physiological and structural traits were measured.…”

“…In the current study we explored how modification of CW hydroxycinnamic acids affect mesophyll CW thickness, g m and other traits related to CO 2 -uptake and water-use. Hydroxycinnamates on arabinoxylan are another unique component of CWs of grasses and other recently evolved monocots, modification of which affects biomass properties (Bartley et al, 2013; Tian et al, 2021; Chandrakanth et al, 2023). Our data suggests that overexpression of OsAT10 , which results in lower CW FA and greater p -CA content, leads to thinner CWs in the transgenics compared to WT plants.…”

“…Instead, xylans (glucuronoarabinoxylan) and mixed-linkage glucan are the principal polymers that interact with cellulose microfibrils in grass primary CW(Cosgrove and Jarvis, 2012). Another feature that distinguishes grass CW from those of dicots is the incorporation of hydroxycinnamates like ferulic acid (FA) and para -coumaric acid ( p -CA) onto arabinoxylan (Chandrakanth et al, 2023). p -CA is also esterified to lignin present in secondary CW thickenings of leaf vascular bundles, and, at lower levels, FA has also been found on lignin of various species (Ralph, 2010; Karlen et al, 2016).…”

A high soluble-fibre allele in wheat encodes a defective cell wall peroxidase responsible for dimerization of ferulate moieties on arabinoxylan

“…This cross-linking is believed to bind AX more tightly into the endosperm cell wall (Saulnier et al, 2007) so decreasing the extent of cross-linking would be expected to increase the amount of WE-AX. Cross-linking of ferulate moities on AX has significance beyond wheat grain as it is a key process in all grass cell walls, determining primary wall extensibility and biomass recalcitrance to digestion and is likely a capability that contributed to evolutionary success of the grasses (Chandrakanth et al, 2023). It has been shown that dimerization of ferulate on AX in grass cell walls requires the action of an apoplastic peroxidase (Burr and Fry, 2009) but the peroxidase gene family is large (Passardi et al, 2004), and the identity of these peroxidases has not been established for any grass cell wall.…”