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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Towards an Understanding of Enhanced Biomass Digestibility by In Planta Expression of a Family 5 Glycoside Hydrolase

In planta expression of a thermophilic endoglucanase (AcCel5A) reduces recalcitrance by creating voids and other irregularities in cell walls of Arabidopsis thaliana that increase enzyme accessibility without negative impacts on plant growth or cell wall composition. Furthermore, our results suggest that cellulose β-1–4 linkages can be cut sparingly in the assembling wall and that these minimal changes, made at the proper time, have an impact on plant cell wall recalcitrance without negative effects on overall plant development.

09 BIOMASS FUELS↗
DOE OSTI2015

Phylogenomic Analyses Indicate that Early Fungi Evolved Digesting Cell Walls of Algal Ancestors of Land Plants

As decomposers, fungi are key players in recycling plant material in global carbon cycles. We hypothesized that genomes of early diverging fungi may have inherited pectinases from an ancestral species that had been able to extract nutrients from pectin-containing land plants and their algal allies (Streptophytes). We aimed to infer, based on pectinase gene expansions and on the organismal phylogeny, the geological timing of the plant–fungus association. We analyzed 40 fungal genomes, three of which, including Gonapodya prolifera , were sequenced for this study. In the organismal phylogeny from 136 housekeeping loci, Rozella diverged first from all other fungi. Gonapodya prolifera was included among the flagellated, predominantly aquatic fungal species in Chytridiomycota. Sister to Chytridiomycota were the predominantly terrestrial fungi including zygomycota I and zygomycota II, along with the ascomycetes and basidiomycetes that comprise Dikarya. The Gonapodya genome has 27 genes representing five of the seven classes of pectin-specific enzymes known from fungi. Most of these share a common ancestry with pectinases from Dikarya. Indicating functional and sequence similarity, Gonapodya , like many Dikarya, can use pectin as a carbon source for growth in pure culture. Shared pectinases of Dikarya and Gonapodya provide evidence that even ancient aquatic fungi had adapted to extract nutrients from the plants in the green lineage. This implies that 750 million years, the estimated maximum age of origin of the pectin-containing streptophytes represents a maximum age for the divergence of Chytridiomycota from the lineage including Dikarya.

Evolutionary Biology↗
DOE OSTI2018

Suppression of a single BAHD gene in Setaria viridis causes large, stable decreases in cell wall feruloylation and increases biomass digestibility

Summary Feruloylation of arabinoxylan ( AX ) in grass cell walls is a key determinant of recalcitrance to enzyme attack, making it a target for improvement of grass crops, and of interest in grass evolution. Definitive evidence on the genes responsible is lacking so we studied a candidate gene that we identified within the BAHD acyl‐CoA transferase family. We used RNA interference (RNAi) silencing of orthologs in the model grasses Setaria viridis ( Sv BAHD 01 ) and Brachypodium distachyon ( Bd BAHD 01 ) and determined effects on AX feruloylation. Silencing of Sv BAHD 01 in Setaria resulted in a c . 60% decrease in AX feruloylation in stems consistently across four generations. Silencing of Bd BAHD 01 in Brachypodium stems decreased feruloylation much less, possibly due to higher expression of functionally redundant genes. Setaria Sv BAHD 01 RNA i plants showed: no decrease in total lignin, approximately doubled arabinose acylated by p ‐coumarate, changes in two‐dimensional NMR spectra of unfractionated cell walls consistent with biochemical estimates, no effect on total biomass production and an increase in biomass saccharification efficiency of 40–60%. We provide the first strong evidence for a key role of the BAHD 01 gene in AX feruloylation and demonstrate that it is a promising target for improvement of grass crops for biofuel, biorefining and animal nutrition applications.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2015

Loss of function of folylpolyglutamate synthetase 1 reduces lignin content and improves cell wall digestibility in Arabidopsis

One-carbon (C1) metabolism is important for synthesizing a range of biologically important compounds that are essential for life. In plants, the C1 pathway is crucial for the synthesis of a large number of secondary metabolites, including lignin. Tetrahydrofolate and its derivatives, collectively referred to as folates, are crucial co-factors for C1 metabolic pathway enzymes. Given the link between the C1 and phenylpropanoid pathways, we evaluated whether folylpolyglutamate synthetase (FPGS), an enzyme that catalyzes the addition of a glutamate tail to folates to form folylpolyglutamates, can be a viable target for reducing cell wall recalcitrance in plants. Consistent with its role in lignocellulosic formation, FPGS1 was preferentially expressed in vascular tissues. Total lignin was low in fpgs1 plants leading to higher saccharification efficiency of the mutant. The decrease in total lignin in fpgs1 was mainly due to lower guaiacyl (G) lignin levels. Glycome profiling revealed subtle alterations in the cell walls of fpgs1. Further analyses of hemicellulosic polysaccharides by NMR showed that the degree of methylation of 4-O-methyl glucuronoxylan was reduced in the fpgs1 mutant. Microarray analysis and real-time qRT-PCR revealed that transcripts of a number of genes in the C1 and lignin pathways had altered expression in fpgs1 mutants. Consistent with the transcript changes of C1-related genes, a significant reduction in S-adenosyl-l-methionine content was detected in the fpgs1 mutant. The modified expression of the various methyltransferases and lignin-related genes indicate possible feedback regulation of C1 pathway-mediated lignin biosynthesis. In conclusion, our observations provide genetic and biochemical support for the importance of folylpolyglutamates in the lignocellulosic pathway and reinforces previous observations that targeting a single FPGS isoform for down-regulation leads to reduced lignin in plants. Because fpgs1 mutants had no dramatic defects in above ground biomass, selective down-regulation of individual components of C1 metabolism is an approach that should be explored further for the improvement of lignocellulosic feedstocks.

59 BASIC BIOLOGICAL SCIENCES↗