Unravelling Chemical Composition of Agave Spines: News from Agave fourcroydes Lem.

Spines are key plant modifications developed to deal against herbivores; however, its physical structure and chemical composition have been little explored in plant species. Here, we took advantage of high-throughput chromatography to characterize chemical composition of Agave fourcroydes Lem. spines, a species traditionally used for fiber extraction. Analyses of structural carbohydrate showed that spines have lower cellulose content than leaf fibers (52 and 72%, respectively) but contain more than 2-fold the hemicellulose and 1.5-fold pectin. Xylose and galacturonic acid were enriched in spines compared to fibers. The total lignin content in spines was 1.5-fold higher than those found in fibers, with elevated levels of syringyl (S) and guaiacyl (G) subunits but similar S/G ratios within tissues. Metabolomic profiling based on accurate mass spectrometry revealed the presence of phenolic compounds including quercetin, kaempferol, (+)-catechin, and (-)-epicatechin in A. fourcroydes spines, which were also detected in situ in spines tissues and could be implicated in the color of these plants' structures. Abundance of (+)-catechins could also explain proanthocyanidins found in spines. Agave spines may become a plant model to obtain more insights about cellulose and lignin interactions and condensed tannin deposition, which is valuable knowledge for the bioenergy industry and development of naturally dyed fibers, respectively

Ectopic callose deposition into woody biomass modulates the nano-architecture of macrofibrils

Plant biomass plays an increasingly important role in the circular bioeconomy, replacing non-renewable fossil resources. Genetic engineering of this lignocellulosic biomass could benefit biorefinery transformation chains by lowering economic and technological barriers to industrial processing. However, previous efforts have mostly targeted the major constituents of woody biomass: cellulose, hemicellulose and lignin. Here we report the engineering of wood structure through the introduction of callose, a polysaccharide novel to most secondary cell walls. Our multiscale analysis of genetically engineered poplar trees shows that callose deposition modulates cell wall porosity, water and lignin contents and increases the lignin–cellulose distance, ultimately resulting in substantially decreased biomass recalcitrance. We provide a model of the wood cell wall nano-architecture engineered to accommodate the hydrated callose inclusions. Ectopic polymer introduction into biomass manifests in new physico-chemical properties and offers new avenues when considering lignocellulose engineering

Transcriptome Mining Provides Insights into Cell Wall Metabolism and Fiber Lignification in Agave tequilana Weber.

Resilience of growing in arid and semiarid regions and a high capacity of accumulating sugar-rich biomass with low lignin percentages have placed Agave species as an emerging bioenergy crop. Although transcriptome sequencing of fiber-producing agave species has been explored, molecular bases that control wall cell biogenesis and metabolism in agave species are still poorly understood. Here, through RNAseq data mining, we reconstructed the cellulose biosynthesis pathway and the phenylpropanoid route producing lignin monomers in A. tequilana, and evaluated their expression patterns in silico and experimentally. Most of the orthologs retrieved showed differential expression levels when they were analyzed in different tissues with contrasting cellulose and lignin accumulation. Phylogenetic and structural motif analyses of putative CESA and CAD proteins allowed to identify those potentially involved with secondary cell wall formation. RT-qPCR assays revealed enhanced expression levels of AtqCAD5 and AtqCESA7 in parenchyma cells associated with extraxylary fibers, suggesting a mechanism of formation of sclerenchyma fibers in Agave similar to that reported for xylem cells in model eudicots. Overall, our results provide a framework for understanding molecular bases underlying cell wall biogenesis in Agave species studying mechanisms involving in leaf fiber development in monocots

Ectopic callose deposition into woody biomass modulates the nano2 architecture of macrofibrils

Plant biomass plays an increasingly important role in the circular bioeconomy, replacing non-renewable fossil resources. Genetic engineering of this lignocellulosic biomass could benefit biorefinery transformation chains by lowering economic and technological barriers to industrial processing. However, previous efforts have mostly targeted the major constituents of woody biomass: cellulose, hemicellulose and lignin. Here we report the engineering of wood structure through the introduction of callose, a polysaccharide novel to most secondary cell walls. Our multiscale analysis of genetically engineered poplar trees shows that callose deposition modulates cell wall porosity, water and lignin contents and increases the lignin–cellulose distance, ultimately resulting in substantially decreased biomass recalcitrance. We provide a model of the wood cell wall nano-architecture engineered to accommodate the hydrated callose inclusions. Ectopic polymer introduction into biomass manifests in new physico-chemical properties and offers new avenues when considering lignocellulose engineering

CHOLINE TRANSPORTER-LIKE1 is required for sieve plate development to mediate long-distance cell-to-cell communication

Phloem, a plant tissue responsible for long-distance molecular transport, harbours specific junctions, sieve areas, between the conducting cells. To date, little is known about the molecular framework related to the biogenesis of these sieve areas. Here we identify mutations at the CHER1/AtCTL1 locus of Arabidopsis thaliana. The mutations cause several phenotypic abnormalities, including reduced pore density and altered pore structure in the sieve areas associated with impaired phloem function. CHER1 encodes a member of a poorly characterized choline transporter-like protein family in plants and animals. We show that CHER1 facilitates choline transport, localizes to the trans-Golgi network, and during cytokinesis is associated with the phragmoplast. Consistent with its function in the elaboration of the sieve areas, CHER1 has a sustained, polar localization in the forming sieve plates. Our results indicate that the regulation of choline levels is crucial for phloem development and conductivity in plants