Biology subjects

Vilaplana, F.

Publications and source records attributed to Vilaplana, F..

4 recordsLinked to original sources

bioRxiv2024

Zymoseptoria tritici stealth infection is facilitated by stage-specific down-regulation of a β-glucanase

Plant cell walls constitute a major defence barrier against pathogens, although it is unclear how specific cell wall components impact pathogen colonisation. Pathogens secrete cell wall degrading enzymes (CWDEs) to facilitate plant colonisation, but damaged, infected cells are often a source of cell wall-derived oligosaccharides that trigger host immunity. The mechanisms by which pathogens minimize the release of cell wall-derived oligosaccharides while colonizing the host remain to be elucidated. We combined biochemical, molecular genetics and transcriptomic analyses to functionally characterize a glycoside hydrolase (ZtGH45) from the wheat pathogen Zymoseptoria tritici. ZtGH45 gene is expressed during the necrotrophic phase of the fungus, coinciding with an accumulation of wheat {beta}-1,3/1,4-mixed-linked glucan (MLG)-derived oligosaccharides. We show that overexpression of ZtGH45 enhances {beta}-1,3/1,4-glucan hydrolysis and the derived oligosaccharides trigger an immune response in wheat, which hinders Z. tritici virulence. The results demonstrate that tight regulation of ZtGH45 is critical for the infection process to prevent early accumulation of MLG oligosaccharides that would prematurely induce host immunity counterbalancing fungal virulence. We suggest that the balance between plant cell wall degradation by fungal CWDE and the release of immunogenic wall-derived oligosaccharides governs the outcome of host invasion by pathogens.

plant biology↗

bioRxiv2024

Transcriptomic analysis of Picea abies tissue culture reveals the impact of culture conditions and the presence of glucuronoxylan on extracellular lignin production

Tissue cultures are an important study model for woody plant tissue and can be used to study lignin biosynthesis. The greatest disadvantage of protocols based on extraction of lignin from wood biomass is the almost inevitable alteration of the native structure of lignin. Using a Norway spruce tissue culture with the ability to secrete monolignols into a liquid culture medium, fundamental aspects of lignin have been studied in the past, such as its structure, the enzyme activity related to its polymerization, and its interactions with a secondary cell wall hemicellulose. In this study, parameters that can induce monolignol production and secretion in the tissue culture are investigated via gene expression analysis. The impact of the composition of the solid growth medium, which was in some cases supplemented with xylan, was studied in depth through transcriptomic investigation. We find that the state (i.e. liquid or solid) and the xylan content of the medium can impact gene expression, although microscopic analysis suggests that cellular morphology is consistent. Extracellular lignin was collected from a formulation of liquid medium with the same composition as that used for cellular growth, which was previously presumed to be "non-inducing" of lignin biosynthesis. Chemical analysis of this lignin was performed using nuclear magnetic resonance spectroscopy and size exclusion chromatography, which revealed changes in its structure compared to the polymer produced in the previously developed "inducing" liquid medium. These experiments show that there is still much we do not understand about an oft-used tissue culture system, but show the way to a deeper understanding of the genetic control of lignin biosynthesis.

plant biology↗

bioRxiv2024

Modification of xylan in secondary walls alters cell wall biosynthesis and wood formation programs

Wood of broad-leaf tree species is a valued source of renewable biomass for biorefinery and a target for genetic improvement efforts to reduce its recalcitrance. Glucuronoxylan (GX) plays a key role in recalcitrance through its interactions with cellulose and lignin. To reduce recalcitrance, we modified wood GX by expressing GH10 and GH11 endoxylanases from Aspergillus nidulans in hybrid aspen (Populus tremula L. x tremuloides Michx.) and targeting the enzymes to cell wall. The xylanases reduced tree height, modified cambial activity by increasing phloem and reducing xylem production, and reduced secondary wall deposition. Xylan molecular weight was decreased, and the spacing between acetyl and MeGlcA side chains was reduced in transgenic lines. The transgenic trees produced hypolignified xylem having thin secondary walls and deformed vessels. Glucose yields of enzymatic saccharification without pretreatment almost doubled indicating decreased recalcitrance. The transcriptomics, hormonomics and metabolomics data provided evidence for activation of cytokinin and ethylene signaling pathways, decrease in ABA levels, transcriptional suppression of lignification and a subset of secondary wall biosynthetic program, including xylan glucuronidation and acetylation machinery. Several candidate genes for perception of impairment in xylan integrity were detected. These candidates could provide a new target for uncoupling negative growth effects from reduced recalcitrance. In conclusion, our study supports the hypothesis that xylan modification generates intrinsic signals and evokes novel pathways regulating tree growth and secondary wall biosynthesis.

plant biology↗

bioRxiv2023

Altering the substitution and crosslinking of glucuronoarabinoxylans affects cell wall porosity and assembly in Brachypodium distachyon.

O_LIThe Poaceae family of plants provides cereal crops that are critical for human and animal nutrition and also they are an important source of biomass. Interacting plant cell wall components give rise to recalcitrance to digestion, thus understanding the wall molecular architecture is important to improve biomass properties. Xylan is the main hemicellulose in grass cell walls. Recently, we reported structural variation in grass xylans, suggesting functional specialisation and distinct interactions with cellulose and lignin. Here, we investigated the functions of these xylans by perturbing the biosynthesis of specific xylan types. C_LIO_LIWe generated CRISPR/Cas9 knockout mutants in Brachypodium distachyon XAX1 and GUX2 genes involved in xylan biosynthesis. Using carbohydrate gel electrophoresis we identified biochemical changes in different xylan types. Saccharification, cryo-SEM, subcritical water extraction and ssNMR were used to study wall architecture. C_LIO_LIBdXAX1A and BdGUX2 enzymes modify different types of grass xylan. Brachypodium mutant walls are more porous, suggesting the xylan substitutions directed by both BdXAX1A andGUX2 enzymes influence xylan-xylan and/or xylan-lignin interactions. C_LIO_LISince xylan substitutions influence wall architecture and digestibility, our findings open new avenues to improve cereals for food and to use grass biomass for feed and the production of bioenergy and biomaterials. C_LI

biochemistry↗