Insights into the molecular regulation of monolignol-derived product biosynthesis in the growing hemp hypocotyl

Abstract

BackgroundLignin and lignans are both derived from the monolignol pathway. Despite the similarity of their building blocks, they fulfil different functions in planta. Lignin strengthens the tissues of the plant, while lignans are involved in plant defence and growth regulation. Their biosyntheses are tuned both spatially and temporally to suit the development of the plant (water conduction, reaction to stresses). We propose to study the general molecular events related to monolignol-derived product biosynthesis, especially lignin. It was previously shown that the growing hemp hypocotyl (between 6 and 20 days after sowing) is a valid system to study secondary growth and the molecular events accompanying lignification. The present work confirms the validity of this system, by using it to study the regulation of lignin and lignan biosynthesis. Microscopic observations, lignin analysis, proteomics, together with in situ laccase and peroxidase activity assays were carried out to understand the dynamics of lignin synthesis during the development of the hemp hypocotyl.ResultsBased on phylogenetic analysis and targeted gene expression, we suggest a role for the hemp dirigent and dirigent-like proteins in lignan biosynthesis. The transdisciplinary approach adopted resulted in the gene- and protein-level quantification of the main enzymes involved in the biosynthesis of monolignols and their oxidative coupling (laccases and class III peroxidases), in lignin deposition (dirigent-like proteins) and in the determination of the stereoconformation of lignans (dirigent proteins).ConclusionsOur work sheds light on how, in the growing hemp hypocotyl, the provision of the precursors needed to synthesize the aromatic biomolecules lignin and lignans is regulated at the transcriptional and proteomic level.Electronic supplementary materialThe online version of this article (10.1186/s12870-017-1213-1) contains supplementary material, which is available to authorized users.

Sucrose synthase gene expression analysis in the fibre nettle (Urtica dioica L.) cultivar “clone 13”

“…The quantification of total lignin was carried out as described previously (Behr et al, 2018) with some modifications concerning the cell wall residue (CWR) preparation. CWR was obtained by washing the powdered plant material first with 70% ethanol three times, followed by washing with acetone and methanol.…”

“…All washing steps were performed at room temperature with agitation for 15 min. Total lignin was determined by using the acetyl bromide protocol as described by Behr et al (2018).…”

Plant Fibers and Phenolics: A Review on Their Synthesis, Analysis and Combined Use for Biomaterials with New Properties

“…Laccases and peroxidases have been used to modify the surface of plant fibers by acting on the encrusting lignin and favor grafting of plant phenolics. Lignin is present in lignocellulosic, as well as in primary and secondary bast fibers (but in very small amounts) of fiber crops like hemp [102]. Laccases and peroxidases are oxidative enzymes that can transform phenols to their phenoxy radicals and are widely used as biocatalysts for different biotechnological applications [103].…”

Transcriptome Profiling of Ornithogalum dubium Leaves and Flowers to Identify Key Carotenoid Genes for CRISPR Gene Editing

“…The monolignol-derived lignins and lignans can strengthen mechanically the xylem by impregnating the secondary cell wall of both tracheary elements and fibers [20], while cuticle or cuticular waxes can provide mechanical strength and viscoelasticity by covering the outer surfaces of the plants [21]. Both above types of compounds mainly function as a physical barrier against pathogen infection, insect attack, UV exposure and high irradiance, as well as preventing water loss from the plant surface [20,21]. These upregulated metabolites may demonstrate evolutionary adaptations by which plants survive and protect the flowers from various environmental stresses.…”