Biology subjects

Pilate, G.

Publications and source records attributed to Pilate, G..

5 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↗

bioRxiv2024

Natural variation in chalcone isomerase defines a major locus controlling growth variation between Populus nigra populations

Poplar is a promising resource for wood production and the development of lignocellulosic biomass, but currently available varieties have not been optimized for these purposes. Therefore, it is critical to investigate the genetic variability and mechanisms underlying traits that affect biomass yield. Previous studies have shown that target traits in different poplar species are complex, with a small number of genetic factors having relatively low effects compared to medium to high heritability. In this study, a systems biology approach was implemented, combining genomic, transcriptomic, and phenotypic information from a large collection of individuals from natural populations of black poplar from Western Europe. Such an approach identified a QTL and a gene, coding for chalcone isomerase (CHI), as a candidate for controlling radial growth. Additionally, analysis of the structure and diversity of traits as well as CHI gene expression revealed a high allelic fixation index, linked to the geographical origin of the natural populations under study. These findings provide insights into how adaptive traits arise, are selected, and maintained in the populations. Overall, this study contributes to enhancing the use of poplar as a valuable resource for sustainable biomass production.

genomics↗

bioRxiv2021

Duplication of NRAMP3 gene in poplars generated two homologous transporters with distinct functions

Transition metals are essential for a wealth of metabolic reactions, but their concentrations need to be tightly controlled across cells and cell compartments, as metal excess or imbalance has deleterious effects. Metal homeostasis is achieved by a combination of metal transport across membranes and metal binding to a variety of molecules. Gene duplication is a key process in evolution, as emergence of advantageous mutations on one of the copies can confer a new function. Here, we report that the poplar genome contains two paralogues encoding NRAMP3 metal transporters localized in tandem. All Populus species analyzed had two copies of NRAMP3, whereas only one could be identified in Salix species indicating that duplication occurred when the two genera separated. Both copies are under purifying selection and encode functional transporters, as shown by expression in the yeast heterologous expression system. However, genetic complementation revealed that only one of the paralogues has retained the original function in release of metals stored in the vacuole previously characterized in A. thaliana. Confocal imaging showed that the other copy has acquired a distinct localization to the Trans Golgi Network (TGN). Expression in poplar suggested that the copy of NRAMP3 localized on the TGN has a novel function in the control of cell-to-cell transport of manganese. This work provides a clear case of neo-functionalization through change in the subcellular localization of a metal transporter as well as evidence for the involvement of the secretory pathway in cell-to-cell transport of manganese.

evolutionary 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↗