Chemical Genetics Uncovers Novel Inhibitors of Lignification, Including p-Iodobenzoic Acid Targeting CINNAMATE-4-HYDROXYLASE

Abstract

Plant secondary-thickened cell walls are characterized by the presence of lignin, a recalcitrant and hydrophobic polymer that provides mechanical strength and ensures long-distance water transport. Exactly the recalcitrance and hydrophobicity of lignin put a burden on the industrial processing efficiency of lignocellulosic biomass. Both forward and reverse genetic strategies have been used intensively to unravel the molecular mechanism of lignin deposition. As an alternative strategy, we introduce here a forward chemical genetic approach to find candidate inhibitors of lignification. A high-throughput assay to assess lignification in Arabidopsis (Arabidopsis thaliana) seedlings was developed and used to screen a 10-k library of structurally diverse, synthetic molecules. Of the 73 compounds that reduced lignin deposition, 39 that had a major impact were retained and classified into five clusters based on the shift they induced in the phenolic profile of Arabidopsis seedlings. One representative compound of each cluster was selected for further lignin-specific assays, leading to the identification of an aromatic compound that is processed in the plant into two fragments, both having inhibitory activity against lignification. One fragment, p-iodobenzoic acid, was further characterized as a new inhibitor of CINNAMATE 4-HYDROXYLASE, a key enzyme of the phenylpropanoid pathway synthesizing the building blocks of the lignin polymer. As such, we provide proof of concept of this chemical biology approach to screen for inhibitors of lignification and present a broad array of putative inhibitors of lignin deposition for further characterization.

The allelochemical MDCA inhibits lignification and affects auxin homeostasis

“…S5). Similar results were found with inhibitors targeting other steps of the lignin biosynthetic pathway (Naseer et al, 2012;Van de Wouwer et al, 2016). The formation of the Casparian strip was rescued by supplying MDCA-treated plants with a mixture of coniferyl and sinapyl alcohol (both end-products of the monolignol biosynthetic pathway, and building blocks of lignin), confirming that MDCA affects the biosynthesis of lignin ( Fig.…”

Cellular and Genetic Regulation of Coniferaldehyde Incorporation in Lignin of Herbaceous and Woody Plants by Quantitative Wiesner Staining

“…This spatial regulation could therefore also depend on the type of coniferaldehydecontaining precursor used to lignify. Metabolomic analyses of lignifying tissues in Arabidopsis and poplar have in fact shown the presence of many phenolic compounds containing coniferaldehyde residues such as b-5-linked dilignols, b-O-4/b-5, and b-O-4/b-O-4-linked trilignols as well as glucosides (Vanholme et al, 2012b;Sundin et al, 2014;Van de Wouwer et al, 2016;Saleme M de et al, 2017). Our results therefore question whether the same coniferaldehyde-containing precursor is used by the different cell types and cell wall layer for lignin biosynthesis.…”

SelectedAspects of Iodate and Iodosalicylate Metabolism in Lettuce Including the Activity of Vanadium Dependent Haloperoxidases as Affected by Exogenous Vanadium

“…On the other hand, 2,3,5-triiodobenzoic acid (2,3,5-triIBeA) plays a role of auxin inhibitor [52]. Van de Wouwer et al [53] revealed that p-iodobenzoic acid (synonym: 4-IBeA) and its derivatives inhibit the process of lignification by reducing the activity of cinnamate 4-hydroxylase-a key enzyme in the phenylopropanoid pathway leading to the synthesis of lignin polymers. Crisan [54] revealed that exogenous 3-iodobenzoic acid (3-IBeA-its content was not determined in our study) stimulated root elongation and the formation of adventitious roots.…”