Biology subjects

Laurans, F.

Publications and source records attributed to Laurans, F..

3 recordsLinked to original sources

bioRxiv2024

Immunolocalization of fasciclin-like arabinogalactan proteins in the G-layers of poplar tension wood fibers

In hardwood trees, tension wood (TW) is an adaptive mechanism used by trees to orient their stems and branches, withstand their own weight, and improve wind resistance. In many species, such as poplar, TW fiber cell walls exhibit a supplemental layer, named the G-layer, which is responsible for the mechanical properties of TW. However, the molecular mechanisms involved still need to be clarified. The synthesis of a number of fasciclin-like arabinogalactan proteins (FLA) has been shown to be highly upregulated during tension wood formation in poplar and is potentially associated with the outstanding mechanical properties of tension wood. Three polyclonal antibodies directed against different poplar TW-specific FLA epitopes were produced and used to assess the presence of these FLAs in differentiating and mature tension wood fibers. Using immunohistochemistry, FLAs were detected at early stages of G-layer differentiation, specifically at the inner side of G-fiber cell walls, whereas a weaker signal was detected in mature G-fibers. However, western blot analyses of protein extracts from differentiating and mature tension wood revealed increased levels of FLA in mature TW fibers, suggesting that these FLAs remained present in mature G layers but were not accessible to anti-FLA antibodies in TW histological sections. Overall, specific FLAs involved in secondary cell wall construction are located at the inner side of the G-layer and are likely actors in the unique mechanical properties of TWs.

plant biology↗

bioRxiv2021

Mechanical characterisation of the developing cell wall layers of tension wood fibres by Atomic Force Microscopy

AO_SCPLOWBSTRACTC_SCPLOWTrees generate mechanical stresses at periphery of stem and branches to improve their strength and to control the orientation of their axes. This key factor in the biomechanical design of trees, named "maturation stress", occurs in wood fibres during cellular maturation when their secondary cell wall thickens. In this study, the spatial and temporal stiffening kinetics of the different cell wall layers were recorded during fibre maturation on a sample of poplar tension wood using atomic force microscopy. The thickening of the different layers was also recorded. The stiffening of the CML, S1 and S2-layers was initially synchronous with the thickening of the S2-layer and continued a little after the S2-layer reached its final thickness as the G-layer began to develop. In contrast, the global stiffness of the G-layer, which initially increased with its thickening, was close to stable long before it reached its final maximum thickness. A limited radial gradient of stiffness was observed in the G-layer, but it decreased sharply on the lumen side, where the new sub-layers are deposited during cell wall thickening. Although very similar at the ultrastructural and biochemical levels, the stiffening kinetics of the poplar G-layer appears to be very different from that described in maturing bast fibres.

biophysics↗

bioRxiv2021

The PMT-driven p-coumaroylation of poplar lignins impacts lignin structure and improves wood saccharification

Transgenic poplars (Populus tremula x Populus alba, clone INRA 717-1B4) were produced by introducing the Brachypodium distachyon Bradi2g36910 (BdPMT1) gene driven by the Arabidopsis (Arabidopsis thaliana) Cinnamate 4-Hydroxylase (AtC4H) promoter in the wild-type (WT) line and in a line overexpressing the Arabidopsis Ferulate 5-Hydroxylase (AtF5H). BdPMT1 encodes a transferase which catalyzes the acylation of monolignols by p-coumaric acid (CA). Several BdPMT1- OE/WT and BdPMT1-OE/AtF5H-OE transgenic lines were grown in the greenhouse and BdPMT1 expression in xylem was confirmed by RT-PCR. The analysis of the cell walls (CW) of poplar stems and of corresponding purified dioxan lignins (DL) revealed that the BdPMT1-OE lignins were as p-coumaroylated as the lignins of C3 grass straws. For some transformants, CA levels even reached about 11 mg/g CW and 66 mg/g DL, which by far exceeds those of Brachypodium or wheat samples. This unprecedentedly high p-coumaroylation of poplar lignins affected neither the poplar growth, nor the stem lignin content. By contrast, the transgenic lignins were structurally modified, with an increase of terminal units with free phenolic groups. Relative to controls, this increase argues for a reduced polymerization degree of BdPMT1-OE lignins and makes them more soluble in cold NaOH solution. The p-coumaroylation of poplar samples, up to the levels of C3 grasses, improved the saccharification yield of alkali-pretreated poplar CW. These results establish that the genetically-driven p-coumaroylation of lignins is a promising strategy to make wood lignins more susceptible to the alkaline treatments that can be used during the industrial processing of lignocellulosics. One-sentence summaryThe expression of a grass p-coumaroyl-CoA:monolignol transferase induces a high p-coumaroylation of poplar lignins and a better saccharification of alkali-pretreated poplar wood without growth penalty

plant biology↗