Michael G Hahn

University of Georgia | UGA · Complex Carbohydrate Research Center

A large and diverse library of glycan-directed monoclonal antibodies (mAbs) was used to determine if plant cell walls are modified by low-gravity conditions encountered during spaceflight. This method called glycome profiling (glycomics) revealed global differences in non-cellulosic cell wall epitopes in Arabidopsis thaliana root extracts recovered...

Postharvest fungal pathogens benefit from the increased host susceptibility that occurs during fruit ripening. In unripe fruit, pathogens often remain quiescent and unable to cause disease until ripening begins, emerging at this point into destructive necrotrophic lifestyles that quickly result in fruit decay. Here, we demonstrate that one such pat...

There is a knowledge gap regarding the factors that impede the ruminal digestion of plant cell walls or if rumen microbiota possess the functional activities to overcome these constraints. Innovative experimental methods were adopted to provide a high-resolution understanding of plant cell wall chemistries, identify higher-order structures that res...

The bulk of plant biomass is comprised of plant cell walls, which are complex polymeric networks, composed of diverse polysaccharides, proteins, polyphenolics, and hydroxyproline-rich glycoproteins (HRGPs). Glycosyltransferases (GTs) work together to synthesize the saccharide components of the plant cell wall. The Arabidopsis thaliana fucosyltransf...

Significance Plant cells are surrounded by an extracellular matrix known as the cell wall. We have analyzed the contribution of the Arabidopsis cell wall to disease resistance to pathogens with different parasitic styles. Here, we demonstrate that plant cell walls are determinants of immune responses since modification of their composition in a set...

A combination of thermochemical pretreatment and biological digestion technologies is usually required to overcome lignocellulosic recalcitrance and accomplish effective biomass deconstruction. This study is aimed at understanding switchgrass breakdown by hydrothermal, dilute acid, dilute alkali, and co-solvent enhanced lignocellulosic fractionatio...

The dynamic endomembrane system facilitates sorting and transport of diverse cargo. Therefore, it is crucial for plant growth and development. Vesicle proteomic studies have made substantial progress in recent years. In contrast, much less is known about the identity of vesicle compartments that mediate the transport of polysaccharides to and from...

Plant cell walls are complex structures subject to dynamic remodeling in response to developmental and environmental cues, and play essential functions in disease resistance responses. We tested the specific contribution of plant cell walls to immunity by determining the susceptibility of a set of Arabidopsis cell wall mutants (cwm) to pathogens wi...

Growing plants with modified cell wall compositions is a promising strategy to improve resistance to pathogens, increase biomass digestibility, and tune other important properties. In order to alter biomass architecture, a detailed knowledge of cell wall structure and biosynthesis is a prerequisite. We report here a glycan array‐based assay for the...

Express and screen : A high‐throughput assay based on the application of azido‐functionalized sugar nucleotide donors on a synthetic glycan array for screening heterologously expressed plant glycosyltransferases was developed. The opportunity to express and screen large numbers of glycosyltransferases instead of rationally selected candidates will...

The lignin biosynthetic pathway is highly conserved in angiosperms, yet pathway manipulations give rise to a variety of taxon-specific outcomes. Knockout of lignin-associated 4-coumarate:CoA ligases (4CLs) in herbaceous species mainly reduces guaiacyl (G) lignin and enhances cell wall saccharification. Here we show that CRISPR-knockout of 4CL1 in p...

There is considerable interest in engineering plant cell wall components, particularly lignin, to improve forage quality and biomass properties for processing to fuels and bioproducts. However, modifying lignin content and/or composition in transgenic plants through down-regulation of lignin biosynthetic enzymes can induce expression of defense res...

The lignin biosynthetic pathway is highly conserved in angiosperms, yet pathway manipulations give rise to a variety of taxon-specific outcomes. Knockout of lignin-associated 4-coumarate:CoA ligases ( 4CLs ) in herbaceous species mainly reduces guaiacyl (G) lignin and enhances cell wall saccharification. Here we show that CRISPR-knockout of 4CL1 in...

Lignocellulosic biomass is highly recalcitrant and requires a pretreatment step to improve the enzyme accessibility and fermentable sugar yields during enzymatic hydrolysis. Our previous studies demonstrated the rearrangement of the hydrogen bond network within CIII, makes it “amorphous-like” and facilitates easier glucan chain extraction by enzyme...

In late 2018, the IPCC recommended that in order to limit global warming to 1.5°C above pre-industrial levels, among other measures, by 2050, up to 85% of global electricity must be supplied by renewable resources, including energy-crops. Miscanthus spp. are promising lignocellulosic crops for biorefining, and their continuing study is paving the w...

Background: Downregulation of genes involved in lignin biosynthesis and related biochemical pathways has been used as a strategy to improve biofuel production. Plant C1 metabolism provides the methyl units used for the methylation reactions carried out by two methyltransferases in the lignin biosynthetic pathway: caffeic acid 3-O-methyltransferase...

Background Lignocellulosic biomass from dedicated energy crops such as Miscanthus spp. is an important tool to combat anthropogenic climate change. However, we still do not exactly understand the sources of cell wall recalcitrance to deconstruction, which hinders the efficient biorefining of plant biomass into biofuels and bioproducts. Results We...

The plant endoplasmic reticulum-Golgi apparatus is the site of synthesis, assembly, and trafficking of all noncellulosic polysaccharides, proteoglycans, and proteins destined for the cell wall. As grass species make cell walls distinct from those of dicots and noncommelinid monocots, it has been assumed that the differences in cell-wall composition...

The plant endomembrane system facilitates the transport of polysaccharides, associated enzymes, and glycoproteins through its dynamic pathways. Although enzymes involved in cell wall biosynthesis have been identified, little is known about the endomembrane-based transport of glycan components. This is partially attributed to technical challenges in...

An indigenous maize landrace from the Sierra Mixe region of Oaxaca, Mexico exhibits extensive formation of aerial roots which exude large volumes of a polysaccharide-rich gel matrix or “mucilage” that harbors diazotrophic microbiota. We hypothesize that the mucilage associated microbial community carries out multiple functions, including disassembl...

Cell walls in crops and trees have been engineered for production of biofuels and commodity chemicals, but engineered varieties often fail multi-year field trials and are not commercialized. We engineered reduced expression of a pectin biosynthesis gene (Galacturonosyltransferase 4, GAUT4) in switchgrass and poplar, and find that this improves biom...

Mitogen-activated protein kinases (MAPKs) cascades play essential roles in plants by transducing developmental cues and environmental signals into cellular responses. Among the latter are microbe-associated molecular patterns perceived by pattern recognition receptors (PRRs), which trigger immunity. We found that YODA (YDA) – a MAPK kinase kinase r...

Background The development of fast-growing hardwood trees as a source of lignocellulosic biomass for biofuel and biomaterial production requires a thorough understanding of the plant cell wall structure and function that underlie the inherent recalcitrance properties of woody biomass. Downregulation of GAUT12.1 in Populus deltoides was recently rep...

Background The development of fast-growing hardwood trees as a source of lignocellulosic biomass for biofuel and biomaterial production requires a thorough understanding of the plant cell wall structure and function that underlie the inherent recalcitrance properties of woody biomass. Downregulation of GAUT12.1 in Populus deltoides was recently rep...

Background Plant cell walls contribute the majority of plant biomass that can be used to produce transportation fuels. However, the complexity and variability in composition and structure of cell walls, particularly the presence of lignin, negatively impacts their deconstruction for bioenergy. Metabolic and genetic changes associated with secondary...

Background Populus natural variants have been shown to realize a broad range of sugar yields during saccharification, however, the structural features responsible for higher sugar release from natural variants are not clear. In addition, the sugar release patterns resulting from digestion with two distinct biological systems, fungal enzymes and Clo...